F610
Orthopedic Problems

Introduction: Orthopedics is the branch of medicine and surgery that is concerned with the health of the bones and associated tissues. There are many types of orthopedic problems that affect dogs. It would actually be unusual for a dog to live its entire life-span without experiencing lameness of one degree or another. Many of these incidents are minor problems that can resolve on their own with rest and time. Minor sprains, twists, or muscle bruises account for a large percentage of these common problems. Persistent lameness, any lameness associated with trauma, and severe lameness problems should always receive the attention of a veterinarian. Recovery from an orthopedic problem may take weeks to months.

Locating the problem area and potential cause: Limping or lameness is one of the more common medical problems encountered by dog owners. Often, the challenge comes when trying to determine the location and then the cause for the lameness. At first, it is important to consider the following questions. These are also questions that a local veterinarian may ask when evaluating the animal:

Note: Basic bone and muscle anatomy of the dog can be found on page A34 of this manual. Pictures of actual radiographs showing different orthopedic problems can be found at the end of this information. The cost involved in treating an orthopedic problem may be substantial. However, the outcome is often good to excellent with proper treatment and patience.

Problems Found in the Front Limb:

1. Shoulder: The shoulder joint is the connection between the scapula (shoulder blade) and the humerus (upper leg). Dislocations and fractures in this area do occur but are unusual in dogs because the shoulder is well-protected by surrounding muscles and other tissues. Arthritis (see below) can also occur in the shoulder joint. Inflammation of a tendon running through the joint and attaching to the biceps muscle is a rather common source of pain in the shoulder. This is called "bicepital tenosynovitis" and may occur because of excessive stress or other shoulder conditions. Growing bone diseases, especially osteochondrosis (OCD) (see below) are relatively common in the shoulder area. The shoulder is also a common location for a deadly type of cancer called osteosarcoma (see below).
   1. Bicepital tenosynovitis is a condition seen mainly in large breed dogs. It can occur simply as a result of excessive exercise or working stress on the shoulder, or it can be secondary to any other shoulder condition. Exact diagnosis of this problem is usually not necessary but may be obtained by x-ray studies with special dye injected into the joint. Treatment consists of rest and the use of anti-inflammatory pain killers. Surgery may be needed in the most severe cases.
      
      
   2. Shoulder joint dislocation can occur as a result of trauma in dogs of any size or breed. X-rays are usually needed to tell the difference between a shoulder dislocation and a fracture. Treatment always requires professional help. Sometimes the dislocation may be successfully treated by moving the bones back into place and wearing a special bandage for 2 weeks. Often, however, surgery is a necessary part of the treatment.
      
      
2. Upper leg (humerus): The humerus is the long bone extending from the shoulder to the elbow. Fractures of the humerus are common. The radial nerve is one of the major nerves in the front limb and travels directly across the surface of the humerus. This nerve can be damaged when the humerus is fractured. Fractures of the humerus are easily diagnosed with x-rays and always require surgery to repair (see figures #1 & #13).
   
   

   Figure 1: Fractured Humerus - This is a fracture in the lower third of the humerus. The black arrow indicates the lower portion of the humerus that connects with the elbow. This type of fracture would need to be repaired surgically.

   
   
3. Elbow: The elbow joint is a "hinge" joint connecting the humerus of the upper front limb to the radius and ulna of the lower front limb. The elbow is relatively unprotected and can be easily damaged and fractured. Dislocations of the elbow joint can also occur but seem to be less common than fractures. Arthritis (see below) of the elbow joint occurs commonly, especially in large breed dogs. A variety of growing bone diseases affect the elbow joint. Some of these are discussed later. Osteochondrosis (OCD) is a growing bone disease affecting many areas of the skeleton and is discussed separately (see below). Bone and joint cancers can affect the elbow joint but seem to do so with less frequency than in other locations in the body.
   1. Fragmented medial coronoid process of the ulna (FMCP) is perhaps the most common cause of pain in the elbow joint of young large breed dogs. The ulna is a complex bone with several small projections at the hinge area where it connects to the humerus. Most of these projections develop separately in the young dog and attach themselves to their proper locations on the ulna as the dog matures. The medial coronoid process is one of these projections or attachments found on the inside surface of the elbow. A developmental "accident" occurs in which the process either attaches and then breaks off or fails to attach itself altogether. This small piece of bone "floats" around in the elbow, causing pain and inflammation. The fragment of bone is often too small to be seen on normal x-rays and may require arthroscopy (camera-assisted surgery) to diagnose. Treatment may be conservative, with anti-inflammatory pain killers and regular, gradually increasing exercise. Surgery to remove the fragment is also a possible treatment option. Arthritis is considered a common consequence of FMCP and seems to occur regardless of treatment.
      
      
   2. Ununited anconeal process (UAP) is another growing bone condition affecting the elbow. The ulna is a complex bone with several small projections. The very top projection, which is part of the hinge mechanism itself, is called the anconeal process. The anconeal process normally grows separately from the main ulna bone in the very young dog, attaching itself at about 4-5 months of age. If the process fails to attach itself, it becomes a source of pain and inflammation in the joint. UAP was first discovered in German shepherds and also occurs in Saint Bernards, Irish wolfhounds, basset hounds, Labrador retrievers, dachshunds, Great Danes, pointers, Newfoundlands, Great Pyrenees, weimaraners, and bloodhounds. UAP is best diagnosed with x-rays (see figure #2). Surgery is considered the best treatment option for most dogs, either by reattaching the process or removing it altogether. Arthritis occurs later on in many cases but may be lessened by early treatment. UAP is considered to have a genetic factor. While the genetics controlling the passing of this condition on to the next generation are complicated, it is recommended that any dog diagnosed with UAP not be bred.
      
      

      Figure 2: Ununited Anconeal Process - The white arrow identifies the anconeal process that has been separated from the rest of the ulna. See figure #14 below for a picture of a normal elbow joint.

      
      
   3. Elbow joint dislocation is uncommon but can occur as a result of severe trauma. The joint is quite stable, and severe trauma is more likely to result in a fractured bone than in a dislocation of the elbow. X-rays are needed to tell the difference between fractures and dislocations of this joint, and occasionally, both a fracture and dislocated elbow will be seen together following a severe blow to a front leg.
      
      Treatment of dislocations requires setting the bones in their proper positions while the dog is under anesthesia. If the procedure can be done within a few hours after the trauma, the setting of the bones can often be performed without surgery. The more time that has passed since the dislocation occurred, the more difficult it becomes to place the bones back in their normal positions. Surgery is necessary to set the bones if they cannot be replaced in their normal positions with anesthesia alone. Placement of a splint or bandage after setting the bones in place may be helpful to achieve rapid healing. Arthritis is common later in life in any joint that has been dislocated.
      
      
4. Lower leg (radius/ulna): The radius and ulna are paired bones that connect the elbow to the carpus or wrist joint. The radius is the major weight-bearing bone of the two. Fractures of the radius and/or ulna are fairly common in dogs (see figures #3 & #15). When fractures of the lower front limb occur, both bones are usually broken together. However, it is not uncommon to have a fractured radius and an intact ulna following trauma to a front limb. X-rays are usually not needed to know whether a fracture of the lower front limb is present but are important to determine the nature of the fracture (see below). Many fractures require surgery, while others can be properly treated with a cast or splint to stabilize the fractured bone(s).
   
   

   Figure 3: Fractured Radius and Ulna: This is a transverse fracture of both the radius and ulna.

   
   
5. Carpus (wrist): The carpus is a very complex structure. There are seven small bones in two rows that connect the lower front limb to the paw and make up the carpal joints. There is a separate joint connecting each row of bones, making a total of three joints in the carpus. Injuries to the carpal joints and bones are common in dogs. Most of these are soft tissue injuries, involving the ligaments and joint capsule only. X-rays are always needed following injury to this area to examine the small bones of the carpus and to determine if any fractures exist. Fractures can occur in any of the bones of the carpus, although they are infrequent. Dislocations of the carpus can occur along any of the joints. If there is severe damage to ligaments and other structures that support the carpus, fusion of the joint (a surgical procedure called arthrodesis) may be necessary. At least one condition related to nutrition in puppies affects the carpus. The radius near its attachment to the carpus is a very common site for a very serious type of cancer known as osteosarcoma (see below).
   1. Hyperflexion deformity is a condition seen in puppies 6-12 weeks of age. The Doberman pinscher breed is most commonly affected. The puppy stands abnormally on both front legs, with the paws seeming to knuckle under. Often, the condition improves on its own within a month or two. Exercise should be restricted, and the puppy should not be fed any nutritional supplements such as vitamin and mineral additives. Some studies show that this condition may be a result of "overnutrition."
      
      
   2. Dislocation of the carpus can occur at any of the three joints as a result of traumatic injury to the front limb. Damage to the ligaments and other tissues that support the carpus is usually difficult to repair and does not heal very well. Special x-ray pictures can help to diagnose a dislocation at one or more of the three joints in the carpus. A dislocation of any or all of these is generally termed "hyperextension." When weight-bearing, a hyperextended carpus allows the paw to drop closer to the ground than normal. The condition is usually quite painful. Minor cases of hyperextension of the carpus may be successfully treated with a splint or bandage and strict rest. However, most hyperextension situations require more aggressive treatment. This is especially true among the medium to large breed dogs. Fusion of the joint, a surgical procedure known as "arthrodesis," is necessary in many cases to restore function.
      
      
6. Paw: The canine front paw is made up of five digits (toes), four of which are weight-bearing. The dewclaw, which corresponds to the human thumb, sits high up on the inside surface of the front paw and does not bear weight. There are five bones called metacarpals that extend from the carpus to each of the five digits. Three bones make up each of the four weight-bearing digits. These bones are called the first, second, and third phalanges. The dewclaw has only two phalanges. The nail bed is a delicate tissue arising from the upper surface of the last phalanx of each digit, and from this tissue each nail grows. A thick, rubbery pad grows on the underside of each paw, and a smaller pad grows on the underside of each of the digits. Lameness that results from pain in the paw is common. Infections of the skin between the digits and around the pads, abrasions of the pads themselves, and a variety of cuts and scrapes all may result in pain and lameness. Fractures of the metacarpals and the digits are also quite common. Finally, cancers of the paw usually arise from the nail bed or the skin. Nail bed cancers can be extremely serious.

Problems Found in the Hind Limb:

1. Pelvis: The pelvis is a bony structure responsible for transferring the weight of the hind end to both hind legs. The pelvis is divided into different areas. Weight is first transferred from the lower spine to bones on the right and left sides. These bones are called the ilia (singular = ilium). The ilia transfer weight to the hip joints. Connecting the right and left sides of the pelvis are two other bone sets known as the pubis and the ischium. The ilia, pubis, and ischium together make up the pelvis, a box-like structure. The acetabulum is the socket-like portion of the ilium that connects to the femur. See figures #16 & #17 for examples of a normal pelvis.  
   
   By far, the most common problem encountered involving the pelvis is trauma and injury. Some estimations report that nearly 25% of all fractures involve the pelvis. Other problems that may involve the pelvis include dislocations, infections of the bone or surrounding tissues, and cancers.
   1. Pelvic fractures are extremely common with trauma of nearly any type. Because of the rigid box-like shape of the pelvis, fractures are always multiple and usually occur in sets of three (see figures #4 & #18). Pelvic fractures range from minor to extremely devastating. Because the right and left ilia are the main weight-supporting portions of the pelvis, fractures of these bones are usually very serious. Fractures of the socket-like acetabulum that houses the ball of the hip joint are also extremely serious and usually end up causing arthritis of the hip later in life, regardless of how well they heal. Fractures of the pubic bone are often minor and are allowed to heal without intervention. Fractures of the ischium vary in severity but are quite often allowed to heal on their own because they usually do not affect the animal’s ability to bear weight. Diagnosis of pelvic fractures is made with x-rays. Treatment depends completely on the situation. Many minor to moderate pelvic fractures can heal very well with strict cage rest and anti-inflammatory pain killers alone. More serious types of fractures, such as those that affect the hip joint or cause changes in the natural shape of the pelvis, should be treated with surgery. Surgery for pelvic fracture repair is extremely difficult and is always expensive. Anti-inflammatory pain killers and laxatives to help reduce pain of normal passage of bowel movements are important aspects of the treatment plan for many pelvic fracture victims.
      
      

      Figure 4: Fractured Pelvis - Notice how the femurs and obturator foramina (white arrows) do not line up. When the pelvis is fractured, it usually breaks in at least three places.  See figures #16 & #17 for examples of a normal pelvis.

      
      
   2. Dislocations of the pelvis are also common with trauma. The only place in the pelvis where a dislocation may occur is at the attachment of the ilium to the spine. This is known as the "sacro-iliac joint." A strong ligament that attaches the ilium to the spine may be torn with severe trauma to the pelvis. Like pelvic fractures, pelvic dislocations are diagnosed with x-rays and treated according to severity and situation. Surgery is often the preferred type of treatment for pelvic dislocations.
      
      
2. Hip: The hip joint consists of the "ball-and-socket" structure connecting the pelvis to the hind limb. The femur is the first long bone in the hind leg that connects the pelvis to the knee or stifle joint. The femur is the longest bone in the body. As discussed previously, the medical term for the socket is the acetabulum. The medical term for the ball is merely the "head" of the femur. See figures #16 & #17 for examples of normal hips. A variety of conditions can affect the hip joint. Fractures and dislocations are common. Arthritis of the hip joint can be crippling to dogs and is discussed in detail later on. A strange condition known as Perthes’ disease affects the hips of young small breed dogs. Cancers of the hip joint area do occur but are rare.
   1. Canine hip dysplasia is a well-known condition, especially among owners of large and giant breed dogs. It has been diagnosed in small and medium breeds as well. Dogs with hip dysplasia are born with normal hip joints, but changes occur during development and aging. Gradual loosening of the joint with swelling, pain, and damage to joint tissues occurs. Months to years may pass, but the final result of hip dysplasia is excruciating pain and crippling in the hind limbs.
      
      There are three main contributing factors in hip dysplasia. The first and probably most important of these is genetics. Because the condition is passed on to future generations, any dog diagnosed with hip dysplasia should not be bred. Screening programs for hip dysplasia in large or giant breed dogs are extremely important and are considered standard procedure for responsible dog breeders. X-rays are taken at two years of age or older and sent to the Orthopedic Foundation for Animals (OFA). Expert radiologists then study the x-rays and provide a score or category for the dog. There are seven total possible scores, of which the top three are considered normal. Most serious breeders will only consider a dog for a breeding program if the result is "Excellent" or "Good," the two top scores. People that purchase a large or giant breed puppy should always ask about the OFA hip score for the breeding parents.
      
      The second factor that is known to contribute to hip dysplasia is diet and nutrition. While less important than genetics in contributing to hip dysplasia, this factor does make a difference and may be controlled by the owners. While in the growing phase (birth to 12 months in most large to giant breed dogs), it is recommended to feed a high-quality puppy formula. Mineral/vitamin supplements are not necessary unless specifically recommended by a veterinarian. Table scraps should be avoided. Treats should be kept to a minimum, although used as needed for training purposes. The high-quality puppy formula should be fed free-choice until the puppy is four months of age. Starting at four months of age, it is recommended to begin free-choice feeding at intervals. Usually, 30 minutes twice daily is sufficient. This means that the puppy is offered as much as it wants to eat for one half-hour every morning and again every evening. This schedule should be followed until the dog is fully mature. Obviously, adjustments may be necessary for each individual puppy. A puppy that eats so much at the half-hour feedings that it becomes sick may require free-choice feedings for only 10 minutes at a time, offered perhaps 3 or 4 times daily. At maturity, the dog should be switched to a high-quality adult formula and fed a measured quantity based on its ideal weight and the recommendations of the specific brand of food. Treats should still be available on a restricted basis only. Over-nutrition and rapid growth in puppies is an extremely common factor that can worsen the situation for an animal prone to hip dysplasia.
      
      The third known contributing factor for hip dysplasia is exercise and activity level. Excessive exercise can lead to inflammation and loosening in the young dog’s joints and contribute to hip dysplasia, as well as other problems. Moderate and controlled exercise is the key for any puppy until it reaches maturity.
      
      Diagnosis of hip dysplasia is made with x-rays. While a local veterinarian may not provide an official OFA score for a dog, he or she can make a diagnosis of hip dysplasia based on x-rays of the hip joints and the pelvis (see figures #5, #19, #20, & #21). There are several options for treatment of hip dysplasia. If diagnosed in a young dog, corrective surgery is available that can help prevent the severe crippling arthritis that results. The surgery is usually very expensive and requires a lengthy healing time. Corrective surgery for older dogs consists generally in a total hip replacement. This is a very difficult and expensive surgery that can have miraculous results for a dog suffering from severe pain in the hips. Medication such as cartilage protectants (glucosamine and/or chondroitin-containing products) and anti-inflammatory pain killers are available, but these drugs have a limited ability to prevent the pain and destruction in hip dysplasia and will eventually fail in many cases. They are also very expensive for large dogs and if used over a long period of time, will likely cost a dog owner as much as surgery.
      
      

      Figure 5: Hip Dysplasia - Notice that the head and neck of the femur (white arrows) are irregular and enlarged. The head of the femur has lost its smooth, round shape and does not fit nicely in the hip socket (acetabulum). See figures #16 & #17 for examples of normal hips.

      
      In summary, hip dysplasia is a challenging disease of the dog skeleton, and treatment is usually expensive. It is best prevented through selective breeding, proper nutrition, and avoiding excessive exercise. More information on hip dysplasia is available under the heading "Arthritis."
      
      
   2. Dislocation of the hip joint is another common result of injury to the hind end in dogs. Blunt force trauma causes the ball to pop out of the socket, tearing the ligaments and capsule that help keep the joint in place. Diagnosis of this condition can often be made by examination by a veterinarian. Confirmation of the dislocation is needed with an x-ray (see figure #6). The x-ray is an important piece of information for proper treatment because it will also show the veterinarian what type of dislocation has occurred. Treatment consists of getting the hip joint back together and keeping it there. This can be more challenging than it sounds. If action is taken quickly, the head of the femur may be put back into place by working the ball back into the socket. This is performed by a veterinarian while the dog is under anesthesia. Because more inflammation in the injured area actually "locks" the bones in their abnormal positions, this procedure becomes increasingly more difficult with the passage of time. If the dislocation cannot be repaired in this manner, surgery becomes necessary to fix the problem. A variety of methods are available, depending on the situation.
      
      

      Figure 6: Dislocated Hip - The white arrow identifies the head of the femur that is dislocated out of the hip socket (acetabulum). Compare this side to the opposite hip that is not dislocated.

      
      A special bandage called an Ehmer sling is usually placed on the leg regardless of the type of treatment used. This sling helps to keep the hip in place while preventing the dog from putting any weight on the leg for up to 2 weeks.
      
      
   3. Perthes’ Disease (also known as "aseptic necrosis of the femoral head"): This condition is not completely understood. It appears that the blood supply to the head of the femur (the ball of the ball-and-socket hip joint) is somehow damaged, leading to the death of part of the bone. This leads to pain in the hip joint. Perthes’ disease usually affects only one hip. Breeds of dogs known to be affected by Perthes’ disease include Yorkshire terriers, West Highland white terriers, dachshunds, Manchester terriers, Cairn terriers, miniature pinschers, poodles, and Jack Russell terriers. Pain and lameness usually start early, between 4 and 10 months of age. A veterinarian can diagnose the condition with x-rays of the hip joints. Mild cases may be treated with strict cage rest and anti-inflammatory pain killers; however, surgery is generally necessary to free the animal from pain.
      
      
3. Upper leg (femur): The femur is the long bone extending from the hip to the knee (stifle). Fractures of the femur are common. Fractures of the femur are easily diagnosed with x-rays and always require surgery to repair (see figures #7 & #22). Repair is often very difficult and can be very expensive.
   
   

   Figure 7: Fractured Femur: This is a transverse fracture of the femur. To adequately fix this type of fracture, orthopedic surgery is required.

   
   
4. Stifle (knee): The stifle joint is another hinge joint like the elbow but vastly different in many ways. The lower portion of the femur ends at the stifle joint. On the front side of the lower end of the femur sits the patella (knee-cap), a small bone that moves up and down as the stifle bends. Small cushions of cartilage sit in between the lower end of the femur and the upper end of the tibia. These cushions of cartilage are called menisci (the lateral meniscus on the outside and the medial meniscus on the inside). Two ligaments run down the sides of the stifle joint, and two ligaments criss-cross inside the stifle joint. All these parts are important in the function of the stifle joint, and all can be injured and lead to pain and lameness.
   
   Injury to the stifle joint is common, and may involve fractures, ligament injuries, or dislocation. Probably the most common injury sustained to the stifle joint is the tearing of one of the inner criss-cross ligaments. This ligament is called the cranial cruciate ligament and is identical to the anterior cruciate ligament in the human knee joint. Improper movement of the patella or knee-cap (called patellar luxation) is also common. Arthritis of the stifle is seen frequently in older patients, usually as a result of some previous injury or problem in the joint. Growing bone diseases such as osteochondrosis (see below) as well as bone cancers may also affect the stifle area.
   1. Cranial cruciate ligament injuries occur very frequently in dogs of all sizes and breeds. Large breeds of dogs are more at risk, however. When the cranial cruciate ligament (CCL) tears, this allows the tibia to slide forward away from the femur too much when the animal bears weight on the leg. This excessive movement stretches the other tissues in the stifle area, resulting in pain. The sliding movement also damages the cartilage cushions (menisci) that sit between the two bones. Most dogs with a torn CCL are very reluctant to bear any weight on the leg. The lameness is usually sudden, although many dogs will have been exhibiting an on-off mild lameness for weeks to months before. Tearing can happen in an otherwise very healthy stifle joint with a sudden and severe blunt force to the area. More commonly, however, the ligament will gradually weaken and deteriorate as the animal ages. Aged, weak ligaments will often tear easily with minor force, such as slipping or jumping. In many of these cases, an owner will not know of any trauma received by the pet. It is important to be aware that these ligaments age and become weak in both stifle joints over time, and when the CCL tears on one side, there is a good chance that the other will also tear in time. This likelihood is probably made even greater with the extra weight borne by the "good" leg when one ligament tears. Overweight dogs are more likely to suffer CCL tears for the same reason.
      
      Diagnosis of CCL tears is made during a detailed examination by a veterinarian. The forward movement of the tibia is detected and helps determine the diagnosis. Some dogs may need to be sedated for a thorough examination if they are too tense. X-rays can also be helpful in showing inflammation in the stifle joint but cannot show the actual torn ligament. Torn cranial cruciate ligaments should always be repaired with surgery. If not repaired surgically, the joint does stabilize itself the best it can with thickening of tissues. The dog will improve gradually up to a limited point after many months of lameness. However, arthritis will always result and is often severe. Thus, if left alone and not repaired with surgery, the dog will usually appear to improve for awhile but will end up getting permanently worse in the end. Once the arthritis sets in, it is irreversible. Prognosis with surgery is usually very good.
      
      
   2. Patellar luxation (dislocation of the knee-cap) is another very common condition of the stifle joint of dogs. This condition occurs in both small and large breed dogs, but the type of luxation is usually a little different between the two. The patella usually dislocates towards the inside of the leg (medially) in small breed dogs, while in large breed dogs, it usually dislocates laterally (toward the outside). The small breed version, known as medial patellar luxation (MPL), is more common.
      
      Trauma to the stifle can cause dislocation in any type of otherwise healthy dog. Patellar instability is graded based on its severity. Grade 1 is the most mild form, while Grade 4 is the most severe. The more mild cases will often gradually progress to become severe later on. Many dogs will adapt to the patella popping in and out of place as they walk. Some dogs may hide this problem so well that the owner may not notice any lameness until the problem is very severe. Arthritis of the stifle is usually a consequence of patellar dislocation.
      
      Diagnosis of this problem is made primarily by physical examination. A veterinarian can detect the abnormal movement of the patella and determine the severity of the problem. X-rays are helpful with the diagnosis, especially in showing if any arthritis is present. Treatment depends on the situation. Mild cases with no lameness present are monitored for worsening of the condition. Severe cases require surgery. There is a large gray zone in the middle of these two extremes. Treatment for cases falling in this gray zone, with only occasional lameness and/or moderate instability, must be judged individually by the owner and the veterinarian. Surgery can be extremely helpful for one particular individual but may not work at all in another. Small-breed medial (inside) dislocation may respond very well to surgery, but success varies according to the individual. Many cases of large-breed lateral (outside) dislocation have other deformities as well and may not respond to any type of treatment very well.
      
      
   3. Stifle dislocation is a very serious problem where numerous ligaments and other tissues have been severely damaged. It requires a great deal of force to cause dislocation of the stifle joint. Dislocation of the stifle joint usually includes tearing and severe damage to both cruciate ligaments and at least one of the menisci. Diagnosis is made by careful examination by a veterinarian while the animal is under anesthesia. X-rays are very helpful as well, showing damage to parts of the joint that cannot be examined from the outside. Treatment is best accomplished by carefully reconstructing the joint. Such a surgery may be lengthy and very expensive. If reconstructive surgery is successful and proper care is taken afterwards for healing, the outcome is often surprisingly good. Mild arthritis and/or stiffness of the joint may result.
      
      
5. Lower leg (tibia/fibula): The tibia and fibula are paired bones that connect the stifle to the tarsus or ankle joint. The tibia is the major weight-bearing bone of the two. Fractures of the tibia and/or fibula are extremely common in dogs. When fractures of the lower hind limb occur, both bones are usually broken together (see figure #8). However, it is not uncommon to have a fractured tibia and an intact fibula following a hind limb trauma.
   
   

   Figure 8: Fractured Tibia and Fibula - The view on the left is looking at the leg from the side. The picture on the right is looking at the leg from the front. This would be considered an oblique fracture.

   
   X-rays are usually not needed to know whether a fracture of the lower hind limb is present but are important to determine the nature of the fracture (see below). Treatment of certain cases requires surgery, while some fractures may be properly treated with a cast or splint to stabilize the fractured bone(s).
   
   
6. Tarsus (ankle): The tarsus or hock joint is a very complex structure. There are seven small bones in two rows that connect the lower hind limb to the paw and make up the tarsal joints. There is a separate joint connecting each row of bones. The calcaneus (heel bone) is the largest of these bones and projects back, toward the dog’s tail. The Achilles tendon (common calcaneal tendon) attaches to this bone and travels up to the muscles on the back of the dog’s lower limb. The Achilles tendon is rather exposed and can be injured easily. Failure of the Achilles tendon also occurs due to fatigue. Injuries to the hock joints and bones are common in dogs. Most of these are soft tissue injuries, involving the ligaments and joint capsule only. X-rays are always needed following injury to this area to help evaluate the small bones of the hock and to determine if any fractures exist. Fractures can also occur in any of the bones of the tarsus. Such fractures are uncommon, except in racing greyhounds that commonly suffer fractures of the calcaneus (heel bone). Dislocations of the tarsus can occur along any of the joints. If there is severe damage to ligaments and other structures that support the tarsus, fusion of the joint (a surgical procedure called arthrodesis) may be necessary.
   1. Dislocation of the tarsus can occur at any of the joints as a result of traumatic injury to the hind limb. Injuries to ligaments in the joint and sometimes fractures of the small bones are associated with hock dislocation. Diagnosis is made by careful examination by a veterinarian and x-rays. Replacement of damaged ligaments, repair of fractured bones, or fusion of the joint, also known as "arthrodesis," may be necessary to restore function.
      
      
   2. Severing of the Achilles tendon is possible as a result of blunt trauma or sharp injuries to the hind limb. Fatigue failure can occur as well, resulting in swelling or even tearing of the tendon. Fatigue failure is usually a result of gradual weakening of the tendon over months to years. This type of injury is more common in dogs that are vertical jumpers, such as Doberman pinschers and other breeds. Fatigue failure results in a tendon that has lost its "spring" and provides little support to the hock joint. Shortening of the tendon can be accomplished with surgery. If the tendon has actually torn, surgery will be necessary to repair it. Some cases respond to splinting or casting the leg at its full stretched length, which helps the tendon to pull tight again as it heals.
      
      
   3. Fractures of the calcaneus (heel bone) are common in racing greyhounds but are infrequent among other breeds. This type of injury is similar to the failure of the Achilles tendon but always requires surgery.
      
      
7. Paw: The canine hind paw is usually made up of four digits, all of which are weight-bearing. The first digit, the dewclaw, which corresponds to the human thumb, sits high up on the inside surface of the hind paw and does not bear weight. The hind dewclaws are missing at birth in dogs more often than they are present. Even when present, a large percentage of hind dewclaws are attached to the paw by soft tissues only. The anatomy and problems associated with the hind paw are identical to the front paw. See above for information on the front paw.

Problems Found in the Spine:

Problems Found in the Skull:

1. Degenerative joint disease (DJD) is the medical term for the extremely common degenerative type of arthritis that occurs in joints. Specific types of DJD have already been discussed, such as hip dysplasia (see above). The main features of DJD are the wearing away of the cartilage and the formation of new bone at the joint margins. Degeneration of a joint can occur as a result of a long list of causes. As discussed in the section on hip dysplasia, genetics, diet, and excessive exercise in a growing puppy can be contributing factors. Previous injury to a joint or nearby structures, infection, and age are also common reasons for this type of arthritis to develop. DJD often gradually gets worse with time and may become extremely severe and even crippling. Any freely mobile joint may become affected, but in dogs the hips, elbows, and stifles are probably the most likely to suffer from DJD. The most common reasons for these joints to develop arthritis are listed in the specific sections for those joints. For example, hip dysplasia is the most common reason for degenerative joint disease in the hips, while tearing of ligaments in the stifle joint is very often responsible for arthritis of that joint. Elbows become arthritic due to a variety of causes, such as fragmented medial coronoid process and ununited anconeal process (see above).
   
   Clinical signs of this degenerative arthritis are generally limited to signs of pain: limping, stiffness, reluctance to exercise, protectiveness and even snapping when painful areas are touched. In severe cases, the patient may stumble or fall frequently, may slip easily on stairs or slippery surfaces, or may become unable to walk at all, if more than one limb is affected.
   
   Because of the decrease in activity often associated with arthritis, dogs may become overweight. This creates what is known as a "vicious cycle," where the additional weight puts extra strain on the joints, which makes the arthritis worse. This causes the dog to exercise or move even less, leading back to more weight gain, and so on.
   
   Diagnosis is based upon physical examination and x-ray films. Treatment for degenerative joint disease is complex. Prevention is by far the most effective way of dealing with any type of arthritis. One very good example is the treatment for a torn cranial cruciate ligament in the stifle joint. Without surgery, the chance of moderate to severe arthritis developing in the joint approaches 100%. If surgery is performed soon after the ligament has torn, however, arthritis will still probably develop but will likely be mild. Once degenerative joint disease has developed for any reason, prevention is not possible and other options must be considered. One approach available for some types of arthritis is joint replacement surgery. Joint replacement surgery is an extremely difficult and expensive treatment, but it may offer the best possible result for some dogs. Total hip replacement for hip dysplasia is available and may offer the best alternative treatment. Other types of surgery may be helpful, such as joint fusion or joint reconstruction. Decisions on whether surgery is an option for treating joints already affected with DJD are best made with the help of an orthopedic specialist.
   
   Medical therapy for DJD is currently a very complex topic. Most dogs with degenerative arthritis will benefit from medical therapy to some degree, and in many cases the improvement is dramatic. Much of this improvement is due to general pain relief. Another benefit of medical therapy is slowing down the progression of disease. There are two main groups of medications that are used to treat degenerative arthritis. The first group consists of anti-inflammatory drugs that help reduce pain and restore function. The second group consists of nutritional supplements containing natural hormones and other products thought to protect the joint tissues from damage and even change and improve the makeup of the joint tissues and fluid.
   
   Many types of anti-inflammatory drugs have been used over the years in the treatment of joint pain and arthritis in dogs. Anti-inflammatory drugs come in two varieties: steroids and non-steroids. Non-steroidal anti-inflammatory drugs are commonly known by the acronym NSAIDs. These include aspirin, acetaminophen, ibuprofen, flunixin meglumine, phenylbutazone, ketoprofen, pirixicam, etodolac, and carprofen. NSAIDs are becoming widely recognized as an important part of the treatment of degenerative arthritis. As dogs become arthritic, the pain of movement naturally leads to decreased exercise and activity. Weight gain then becomes a common problem in less mobile pets. Extra weight increases stress on the arthritic joints, leading to increased inflammation and pain. The additional pain then causes the dog to become even less mobile, and the "vicious cycle" mentioned previously continues. Perhaps the greatest benefit of NSAID use in dogs with arthritis is the breaking or hindering of this vicious cycle. Use of anti-inflammatory pain killers can keep an arthritic dog moving and exercising, thus maintaining a healthy weight and slowing down the progression of joint disease.
   
   Many different types of NSAIDs have been listed previously. This is not an indication that all are recommended or healthy for use in dogs. In fact, NSAIDs are drugs that tend to have a rather narrow margin of safety, which means that it is quite easy to create problems with them. Side effects of NSAID use include vomiting, listlessness, loose stools, and hives. It is recommended to give NSAIDs to a dog only under the supervision of a veterinarian and to use only those that have been specifically tested and approved for dogs, such as etodolac (EtoGesic) and carprofen (Rimadyl - see page G712).
   
   Steroids can be used for their powerful anti-inflammatory effects in dogs, but they are usually reserved for the most severe cases that fail to respond to NSAIDs. Steroids are less likely to produce the long term benefits that the NSAIDs can, mainly due to side effects such as weight gain.
   
   A second major group under medical treatment of DJD is nutritional supplement therapy. Glycosaminoglycans (GAGs) are substances naturally found in joints and, specifically, cartilage. They are very important in maintaining healthy joints. Several products are marketed with either the actual glycosaminoglycan substance or the necessary building blocks the body needs to produce them. Chondroitin sulfate is probably the most abundant and commonly marketed GAG. It can be extracted from cow, whale, and shark tissues. Glucosamine is an important building block for production of GAGs in the body. It is commonly marketed along with chondroitin sulfate for joint health in both people and animals. It is marketed under three major types: glucosamine hydrochloride, glucosamine sulfate, and glucosamine hydroiodide. All three appear to be equally effective. Some dog foods have started marketing their products with added glucosamine and/or chondroitin. It is thought by many nutritionists and veterinarians that these products do make a difference if used over long periods of time. Studies in people have found that these products do preserve motion in the joints and help control joint pain. Glucosamine and chondroitin sulfate function in different ways and appear to work best when given together. Some glycosaminoglycans may be given as weekly or twice-weekly injections, but most are given as daily oral tablets or powders. Another product that is commonly given is methylsulfonylmethane (MSM). This is a naturally occurring dietary sulfur that is a derivative of dimethyl sulfoxide (DMSO). It acts as an anti-inflammatory and general pain reliever. Perhaps the major problem with nutritional arthritis therapy is the lack of regulatory control over these products. It is probable that the quality and quantity of the supplement varies significantly from product to product. Most veterinary clinics sell supplements that they feel contain a quality product for a reasonable price. Examples of such products include Methylsulfonylmethane (MSM) (see page H506), Adequan (see page H12), and Glyco-Flex III (see page H280).
   
   
2. Infectious arthritis is the condition where an infection leads to inflammation of a joint. There are several different types of organisms that can infect the joints. Examples of bacterial infections, protozoal infections, and fungal infections of joints will be discussed. Viral joint infections occur in humans but are not known to occur in dogs at this time.
   1. Septic arthritis is the condition where a joint becomes infected with bacteria, usually from a penetrating injury or bite wound. This particular type of arthritis is discussed below.
      
      
   2. Lyme disease: Lyme disease is a type of infectious arthritis that is caused by a specific bacteria called Borrelia burgdorferi. Borrelia burgdorferi is spread by only one genus of tick, Ixodes, which lives in specific areas. In the United States, Lyme disease is problematic in the northeast states, north central states (northern Minnesota and Wisconsin), and northern California/southern Oregon areas. Episodes of lameness in one or more joints occurs typically, along with inflammation and swelling of lymph nodes, lack of energy, and fever. Diagnosis is sometimes difficult, but serology and culture of joint fluid may be helpful. X-rays of affected joints may also be beneficial in some cases. Antibiotics are used for treatment of Lyme disease and are usually quite effective in a 3-4 week course. Products for tick prevention and vaccination against Lyme disease itself can help prevent this type of infectious arthritis. For more information on Lyme disease, see page F498.
      
      
   3. Mycoplasmal arthritis: Mycoplasma are small bacteria that are difficult to culture and can sometimes be difficult to treat. Fortunately, this type of bacterial arthritis is very uncommon. Mostly, sick or debilitated dogs develop this type of arthritis secondary to a respiratory or urinary tract infection. Diagnosis is made with special tests performed on joint fluid. Treatment with antibiotics such as erythromycin, tylosin, or gentamicin is usually recommended.
      
      
   4. Rocky Mountain spotted fever: This type of infectious arthritis is caused by a bacteria-like microorganism known as Rickettsia rickettsii that is spread by a tick. The genus of tick that carries Rocky Mountain spotted fever is known as Dermacentor and is found in the wooded areas of the central United States and eastern seaboard. The disease is very serious and may result in sudden death. Walls of small blood vessels are attacked and destroyed by the infection. This leads to bruising and bleeding, death of tissues due to a lack of blood supply, and inflammation of the eye, brain, and joints. Treatment with antibiotics should be initiated as soon as possible following infection to minimize the extent of disease. Tick control is very important in the prevention of Rocky Mountain spotted fever. See F988 for additional details.
      
      
   5. Ehrlichiosis: Canine ehrlichiosis is another tick-borne disease caused by a rickettsia. The brown dog tick, Rhipicephalus sanguineus, is the tick species related to the spread of canine ehrlichiosis. The infection causes damage to bone marrow and many other body systems. Arthritis of several joints may occur early or late in the course of the infection. Serology is usually used to diagnose this infection. Supportive care and aggressive doses of antibiotics are the basic treatments for canine ehrlichiosis. Tick control is probably the best method of prevention.
      
      
   6. Leishmaniasis: Leishmaniasis is a disease caused by a protozoal microorganism called Leishmania donovani. The sandfly serves as the main insect carrier for Leishmaniasis. Areas where this disease occurs include the Mediterranean, Africa, South America, and Asia. Most infected dogs develop skin disease; lymph nodes, kidneys, eyes, and joints may become inflamed as well. Diagnosis of Leishmaniasis is made with laboratory testing of blood and swollen lymph node samples. Anti-protozoal drugs do exist for Leishmaniasis treatment, but the most effective are not available in all areas. Prevention is difficult in areas where Leishmaniasis occurs. The best prevention advice for owners in non-endemic areas is not to travel with their pets to endemic locations.
      
      
   7. Fungal arthritis: Fungal joint infections most often occur secondary to fungal bone infections (see below under "Infections"). A variety of fungal types may infect the joints of dogs. Diagnosis is best made with special testing of the joint fluid. A lengthy treatment with antifungal drugs is often necessary.
      
      
3. Immune-based arthritis is the third category of arthritis in dogs. The term "immune-based" indicates that these types of arthritis involve the animal’s own immune system destroying the joint tissues. Immune-based arthritis is typically a disease of multiple joints. This category is split into two subsections titled erosive and nonerosive. Because there is always destruction of the bone that borders the affected joint, erosive-type arthritis is visible on an x-ray film. X-ray films of nonerosive arthritis are essentially normal.
   1. Erosive immune-based arthritis:
      1. Rheumatoid arthritis is an uncommon type of arthritis in dogs where the immune system forms antibodies against the joint tissues. These antibodies then find joint tissues and stick to them, acting as a flag to the rest of the immune system. Slowly, the tissues become swollen and painful as the attack continues and the joints try to respond by healing and protecting themselves from the immune system. Why the antibodies form against joint tissues in the first place is not completely known. However, distemper virus has been found in the joint tissues of many dogs with rheumatoid arthritis, indicating a possible link.
         
         Any breed of dog may be afflicted with rheumatoid arthritis. Most affected dogs are fully grown, and the average age when signs begin is around 6 years. Lameness is the principal symptom noticed by dog owners and can range from mild to severe. While multiple joints are usually affected with rheumatism, the dog may experience pain in only one or two joints. Sometimes, the lameness appears to shift from one joint to another. Joints may become swollen and deformed in time.
         
         Diagnosis of rheumatoid arthritis is somewhat complex, generally requiring x-ray films, joint fluid analysis, and blood testing. Similar to people, rheumatoid arthritis is not curable and is generally treated with a variety of anti-inflammatory drugs. NSAIDs, steroids, gold injections, and other types of therapy have been attempted with some success. Limited response has been seen with some types of surgery. Rest and elimination of stress are important in treatment of rheumatoid arthritis.
         
         
      2. Greyhound polyarthritis is an erosive immune-based arthritis seen only in the greyhound. Most affected dogs gradually become lame before age 3. This type of arthritis appears similar to rheumatoid arthritis, but there is evidence that Mycoplasma bacteria (see above) may be responsible and that this type of arthritis should be categorized as an infection. Diagnosis and treatment of greyhound polyarthritis are similar to rheumatoid arthritis.
         
         
   2. Nonerosive immune-based arthritis:
      1. Systemic lupus erythematosus (SLE) is an uncommon disease in dogs that affects multiple systems in the body at one time. Disorders of the nervous system, respiratory system, kidneys, skin, muscle tissue, blood, and joints are commonly seen with SLE. Multiple joints typically become swollen and painful. Affected animals may be listless, have a decreased appetite, and may have a high temperature. If the kidneys begin to fail, an increased thirst and need for urination may develop. Skin problems are common and are described in more detail on F770. Because SLE tends to involve so many systems, diagnosis of this disease is challenging. Tests that may be helpful in the diagnosis of SLE include testing for antibodies the immune system creates to attack other tissues of the body, also known as "autoantibodies;" x-ray films, joint fluid tests, and bloodwork. Treatment is generally focused on suppressing the immune system with steroids and other drugs. The expected outcome is not usually good and becomes very grim if the kidneys begin to fail.
         
         
      2. Breed-specific polyarthritis: This is a group of uncommon to rare conditions specifically seen in certain dog breeds where the immune system is responsible for swelling and pain in the joints and sometimes in other parts of the body as well. Most of these conditions are difficult to treat and carry a rather poor prognosis. These include the following:
         • Polyarthritis/polymyositis syndrome: Seen most often in spaniel breeds. Inflammation occurs in joints and muscle tissue.
         • Polyarthritis/meningitis syndrome: Seen in weimaraners, pointers, boxers, Akitas, and Bernese mountain dogs. Inflammation occurs in joints and the meninges (tissue lining the brain and spinal cord). Severe neck pain and difficulty walking may be seen.
         • Familial renal amyloidosis: Also known as the "hot hock syndrome," this is a disease found in Chinese shar peis. Hock joints become inflamed, swollen, and painful. Failure of other organs, especially kidneys, usually results in a very poor outcome.
         • Heritable polyarthritis of the adolescent Akita: As described in the name, young Akitas are affected. Inflammation of joints, lymph nodes, and other organs may occur.
         • Polyarteritis nodosa: This uncommon condition may be seen in a variety of breeds and is often called "stiff beagle disease" when it occurs in young beagles. Joints, meninges (protective tissue around the brain and spinal cord), and muscles may become inflamed. Severe neck pain is often present if the meninges are involved. Because it can gradually go away on its own, this condition may have a good outcome when it occurs in young dogs.
           
           
      3. Idiopathic polyarthritis is a "catch-all" category where all other unknown causes of multiple joint pain and swelling are placed. About half of the arthritis cases placed into this category appear to result from illness elsewhere in the body. Three types of illness located in other parts of the body can lead to this type of arthritis, although it is usually unclear how this happens. First, infections in various places including the lungs, tonsils, urinary tract, skin, and eyes have been linked with idiopathic polyarthritis. Disease of the digestive tract including inflammation of the stomach, intestines, and colon is another cause of idiopathic polyarthritis. The third cause is cancer of remote areas including breast cancers and some types of cancer involving the heart, reproductive tract, and skin. If arthritis of several joints occurs due to any of these underlying conditions, the treatment must focus on the specific condition. If an underlying cause can be treated and removed, the arthritis will usually go away. The other half of cases diagnosed with idiopathic polyarthritis do not have any known underlying cause for the problem. Most of these cases respond well to treatment with steroid therapy.

1. Primary bone cancers: Osteosarcoma, chondrosarcoma, fibrosarcoma, and hemangiosarcoma are the four most prevalent primary bone cancers seen in dogs. Osteosarcoma is by far the most common.
   1. Osteosarcoma is the most common bone cancer in dogs and arises from bone cells. This type of bone cancer is extremely aggressive and usually spreads very quickly to other parts of the body. Most at risk are large and giant breeds such as the St. Bernard, Great Dane, Irish setter, Doberman pinscher, boxer, and German shepherd. Middle-aged to older dogs tend to be affected most often, although osteosarcoma has been seen in a 6 month old puppy. Osteosarcoma can arise from any bone of the skeleton. About 80% of this type of bone cancer occurs in the long bones of the limbs. The other 20% can occur in the skull, spine, ribs, and other bones. In the limbs, the most common places where osteosarcoma occurs are the shoulder (upper humerus), carpus (lower radius), and knee (both lower femur and upper tibia).
      
      The cause of osteosarcoma in dogs is unknown in most cases. A higher risk does seem to be associated with any abnormal bone (i.e. affected by another bone disease), places where a fracture occurred in the past, and with metal hardware, such as screws or pins in a previously broken bone. Radiation may also be a cause of bone cancer. However, since most dogs affected with bone cancer do not fit into any of these possible categories, it is usually impossible to give a reason for its occurrence.
      
      The most obvious clinical signs of osteosarcoma include pain and swelling in the affected area. When the bone cancer occurs in one of the limbs, lameness is often very obvious early on. Depending on where the cancer occurs, swelling of the affected area may become obvious to an owner. Another clinical sign may occur where the cancer, after weakening the bone from which it grows, allows the bone to break through the weakened area. This is known as a pathologic fracture– a fracture of a bone resulting from some underlying cause. When such a fracture occurs, sudden lameness, inability to bear weight, pain, and swelling at the fractured area result.
      
      Diagnosis of osteosarcoma begins with x-rays of the affected bone. Trained professionals can come to a very high degree of suspicion for osteosarcoma just by looking at a good quality x-ray (see figure #11). For a complete diagnosis to be made, a biopsy of the cancerous tissue must be sent to a laboratory for histopathology. A bone biopsy is a tricky procedure with the undesirable side effect of further weakening the diseased bone. Treatment for osteosarcoma is so aggressive and drastic, however, that an accurate diagnosis is very important. The benefits of knowing the diagnosis outweigh the risks of obtaining a bone biopsy in most cases. Once the diagnosis of osteosarcoma is made, treatment should be started as soon as possible. Treatment of osteosarcoma begins with aggressive removal of the affected bone. Amputation of the entire affected limb is the standard approach for osteosarcoma of the long bones of the legs. For osteosarcoma of a rib, surgery can be performed to remove the cancerous tissue and replace the rib with a special mesh or other supportive material. Complete removal of skull or spinal osteosarcoma may be extremely difficult to impossible depending on how extensive the tumor has spread.
      
      

      Figure 11: Osteosarcoma: The white arrow identifies the center of an osteosarcoma tumor in the top section of the humerus.

      
      A rather recent alternative to amputation can be offered for some patients. This technique, known as limb-sparing surgery, was developed to save the affected limb from amputation. The cancerous portion of the bone is removed and replaced with a section of healthy donor bone from another dog. The donor bone is secured with a metal plate to the original bone. This surgery is very expensive but an attractive alternative for some owners not wishing to have their pet’s limb amputated. The technique does not appear to affect the survival rate of dogs when compared with amputation. Most often the technique has been used with osteosarcoma near the carpus (lower radius). Shoulder (upper humerus) osteosarcoma may also be treated in this way, but recovery from surgery usually takes longer. Osteosarcoma of the hind limb is usually not treated with limb-sparing surgery.
      
      Most of the time, the cancer has already spread to the lungs (see figure #23 below) by the time the diagnosis is made. Chemotherapy can help slow the growth of the cancer wherever it has spread for months to sometimes years. A veterinarian specializing in cancer treatment may make the best recommendation on chemotherapy based on the most current information available. Prognosis without treatment of any kind is poor, with the pain increasing in intensity very quickly. Amputation alone for osteosarcoma of a limb can provide wonderful relief from pain to a pet, but without additional treatment (i.e. chemotherapy) survival rates for these animals is usually only 4 or 5 months. With amputation and chemotherapy, months to years may be added to the life of a pet. The sad news is that eventually nearly all patients diagnosed with osteosarcoma will die from the disease sooner or later.
      
      
   2. Chondrosarcoma is a primary bone cancer that arises from cartilage cells within the bone. It is far less common in the limbs than osteosarcoma but does occur with some frequency in the ribs and skull. It can occur in any area of the skeleton. This type of bone cancer is very aggressive but has a lower rate of spreading to other areas in the body than does osteosarcoma; this is another reason why it is important to make a complete diagnosis based on bone biopsy. Diagnosis consists of x-rays followed by biopsy of the affected bone. Treatment consists of aggressive surgical removal. Radiation therapy has been used in chondrosarcoma therapy, but success has been variable. Currently, chemotherapy is probably the least useful cancer treatment for chondrosarcoma.
      
      
   3. Fibrosarcoma is a cancer arising from connective tissue found throughout the body, including bone tissue. It occurs only rarely in bone but may be difficult to treat. Diagnosis is made by bone biopsy. Fibrosarcoma of bone, in contrast to other tissues, is more likely to spread to other areas of the body and cause further disease and even death. Aggressive surgery is considered the best treatment.
      
      
   4. Hemangiosarcoma is a cancer of blood vessel cells that rarely occurs in bone. When it does occur in bone, spreading to other tissues is very common and the affected dog most often suffers from secondary spreading to brain, lungs, liver, and other organs.
      
      
2. Primary joint cancers:
   1. Synovial sarcoma is an uncommon cancer arising from cells in and around the joints. In dogs, synovial sarcomas seem to affect the knee joint most frequently, followed by the elbow joint. Lameness is the most common sign noted with this cancer type. The average age of affected dogs is 7-8 years old.
      
      Diagnosis is made with x-rays and biopsy. Amputation of the affected leg is standard treatment for synovial sarcoma, with the possibility of chemotherapy. The outcome is good to fair with amputation of the affected leg, and some cases may go up to 2 years without recurrence.
      
      
3. Secondary bone cancers: Tumors that spread from other areas of the body to bone are called secondary bone cancers. Spreading can occur through the blood supply to bone from distant places in the body or from tumors that grow right next to the bone and invade it. Most commonly, secondary cancers occur in bone from nearby tumors that invade and attack all tissues nearby. Many cancers that start in the mouth and in the toes (especially the nail bed tissue) are especially prone to invade bone. Distant spreading can occur from cancer of the lungs, liver, thyroid gland, prostate gland, and mammary gland (breast cancer). Sometimes the source of the cancer is not known until a biopsy is obtained of the affected bone and a veterinary specialist finds, for example, cancerous thyroid gland cells within the bone. Treatment of spreading secondary bone cancer depends on the nature of the cancer. Treatment of the original tumor is usually of more importance than treatment of the secondary bone cancer. Surgery, chemotherapy, or radiation therapy may be feasible treatment options.

Fractures:

1. Classification of fractures:
   1. Closed or simple fracture: This is a fracture of a bone where the skin is not broken and no communication to the outside environment has occurred. It is opposite of an open or compound fracture.
   2. Open or compound fracture: This is a fracture where communication with the outside environment has occurred. Examples include gunshot injuries to bones and fractures where the sharp bone fragments have cut through the skin.
   3. Transverse fracture: This is a fracture where the bone is broken into two pieces and the fracture crosses the bone in a straight, side-to-side line.
   4. Oblique fracture: This is a fracture where the bone is broken into two pieces and the fracture crosses the bone in a diagonal line.
   5. Spiral fracture: This is a fracture where the bone is twisted apart.
   6. Comminuted fracture: This is a fracture where the bone is broken into multiple pieces.
   7. Greenstick fracture: This is a fracture where the bone is broken on one side, with the other side bent but not fractured. This type of fracture is most commonly seen in young puppies.
   8. Pathologic fracture: This is a fracture due to a weakened bone structure from any disease process (i.e. bone cancer, infection, or osteoporosis).
   9. Stress fracture: This fracture results from repeated force to a bone. This type of fracture is most commonly seen in performance dogs.
   10. Segmented or double fracture: This is a bone that is broken in two or more different places.
       
       
2. Managing fractured bones: The first part of treatment of a broken bone is often done by the dog’s owner. Since most fractures are associated with some kind of trauma, checking the vital functions of the injured pet should always be done first. Alertness, breathing status, and mucous membrane color/capillary refill time should be observed quickly and thoroughly. The pet’s responsiveness and state of awareness can help assess whether the brain and central nervous system are functioning on a basic level. Difficulty breathing may result from internal bleeding, broken ribs, or other injuries. Pale gum color with a slow capillary refill time occur with severe blood loss and shock. These are potential life-threatening injuries that must take precedence over any broken bones. Rapid transport to a veterinary hospital is very important for trauma patients. Specific home treatment for a broken bone can be done if there is time and if the patient is cooperative. Handling an injured pet should always be done with caution– even the most trustworthy pet may bite its owner when injured. If a wound is present in association with a broken bone, a clean bandage may be placed on the injury. Direct pressure should be used to control any bleeding from an injured limb. See page E200 for additional emergency treatment information.
   
   Once the patient is brought into the veterinary hospital, the veterinary staff takes over, repeating the steps listed above. Beginning with the vital signs, the patient is examined thoroughly. Life-threatening injuries are given attention first, followed by fractured bones. A patient must be stabilized before a broken bone is given treatment; this stabilization process may require hours to days. A bandage is usually placed on a fracture to help control pain and prevent further injury until proper treatment can begin. Once the patient is stable, plans for treating broken bones may be made.
   
   Specific treatment for a broken bone depends greatly upon the situation. The location and type of fracture, availability of specialist help, nature of the patient, and cost are all factors that influence how a broken bone will be treated. Some veterinarians specialize in orthopedic surgery and should become involved in the more complex bone injuries. Because they usually require a great deal of time, personnel, and training to properly treat, the cost of treating broken bones is generally high.
   
   There are various methods of fixing broken bones. The broken bone must be placed into the proper position and held there with some type of supporting device. Splints and casts are rigid supports that encircle the broken limb and can be used for a variety of fractures, but have limitations on how much they can do. These types of outer support can be used with or without internal support for the broken bone, depending upon the situation. Other types of support for broken bones may require extensive surgery. Metal pins inserted into the bone (see figure #12), wires that encircle the fracture and tighten against the outside of the bone, and metal plates that cross a fracture and are screwed into the bone are all common types of internal support that are used. External skeletal fixation is another type of support that is becoming more common in veterinary medicine. This type of support is both internal and external because several metal pins are drilled at a right angles to the bone with the pin sticking out of one and sometimes both sides of the leg. These pins are then connected to each other with another metal rod or bone cement, creating a support on the outside of the body. The type of support used to treat any given fracture depends upon many factors and is best left to the discretion of the veterinarian.
   
   

   Figure 12: Osteomyelitis - The black arrows identify just one area of osteomyelitis surrounding the humerus. The white arrow identifies a bone pin placed to repair a previous fracture.

Infections:

Figure 13: Fractured Humerus - This is a fracture in the lower third of the humerus.

Figure 14: This is a completely normal elbow joint.

Figure 15: Fractured Radius and Ulna: This is a transverse fracture of both the radius and ulna.

Figure 16: This is a completely normal pelvis. The hip sockets and head of each femur are also normal. Notice the smooth, rounded head of each femur and how they fit nicely into each hip socket (acetabulum).

Figure 17: This is also a completely normal pelvis. The hip sockets and head of each femur are also normal.

Figure 18: Fractured Pelvis - Notice how the obturator foramen (white arrow) is not a smooth "circle." When the pelvis is fractured, it usually breaks in at least three places.

Figure 19: Hip Dysplasia - Notice that the head and neck of the femur (white arrows) are irregular and enlarged. The head of the femur has lost its smooth, round shape and does not fit nicely in the hip socket (acetabulum).

Figure 20: Another picture of hip dysplasia - The neck of each femur (white arrows) is severely thickened.

Figure 21: Another picture of hip dysplasia.

Figure 22: A severely fractured femur.

Figure 23: This is a picture of tumors in the chest of a dog. These tumors spread here from another location in the dog's body. The white arrows identify only some of the masses.