F610
Orthopedic Problems

problems found in the front limb | problems found in the hind limb | problems found in the spine | problems found in the skull | arthritis | degenerative joint disease | anti-inflammatory drugs | infectious arthritis | immune-based arthritis | growing bone diseases | neoplasia | fractures | classification of fractures | managing fractured bones | infections | osteomyelitis | septic arthritis

Introduction: Orthopedics is the branch of medicine and surgery that focuses on the health of the bones and associated tissues. There are many types of orthopedic problems that affect cats. 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 problems encountered by cat 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:

  1. What is the activity level of the cat?
  2. Have there been any prior surgeries or medical problems?
  3. What is the animal’s age, sex, breed, size, diet, and life-style? (For example, an outdoor cat that frequently gets into cat fights is much more likely to sustain a bite wound that becomes infected and leads to lameness than a cat which is kept strictly indoors.)
  4. Is the cat currently on any medications?
  5. Has the condition come on suddenly or slowly?
  6. Does the problem seem to be associated with an injury?
  7. Does the problem get worse after exercise?

A thorough physical and orthopedic examination should then be performed. The goal of an examination is to identify the location of the lameness. The following are some basic steps that are often used when performing an orthopedic exam:

  1. The cat should be observed while standing. Signs of muscle shrinking (atrophy), confirmation abnormalities, swelling, and pain can often be found.
     
  2. Next, the patient is observed from the front, side, and rear while walking and possibly jumping up onto a chair or table. When the lame limb contacts the ground, the stride of the affected limb is usually shortened as compared to the opposite, normal limb. When the sound limb hits the ground, the animal will often spend more time with that limb in contact with the ground during the walking motion. Other problems that are often noticed include ataxia (lack of coordination), paralysis, paresis, and short, choppy gaits. If more than one limb seems to have a problem, a more central condition may be at fault. It is important to remember that a perfectly normal gait requires the use of almost the entire nervous system and many of the muscles and bones of the body. Injury, damage, or tumors that affect the nervous system, muscles, or bones can cause problems in one, two, or all four limbs.
     
  3. Once the problem limb(s) is identified, a thorough examination of the limb(s) is necessary to further localize the problem. The examination must be systematic, starting at one end of the limb and proceeding up or down, feeling every bone and every joint in the limb. Each area of the limb, including muscles, bones and tendons, is felt (palpated) as gently as possible until the painful area is identified. All this should be done while the animal is fully awake without any sedation. Sedation may mask the animal’s response to the testing. Each joint is moved through the entire range of motion by flexing, extending, and rotating. Each joint should also be felt for evidence of swelling, pain, heat, lack of motion, instability, crepitus (popping), and laxity.

    Abnormal laxity (slackness) may indicate ligamentous injury or damage to the joint capsule. Some fractures are often very obvious, while others may only be identified by excessive movement of the area, pain, swelling, and lack of use of the limb. A hot, swollen joint often is the result of an infection causing inflammation. If the injury has caused the animal to avoid using the limb(s) for a period of time, the muscles may shrink (atrophy). Injury to muscles is often identified by tenderness, swelling, pain, and heat.
     
  4. After a specific area of injury has been identified, radiographs (x-rays) are often used to help determine the extent of the damage and determine the appropriate treatment.

Note: Basic bone and muscle anatomy of the cat can be found on page A34 of this manual. Pictures of actual radiographs showing different orthopedic problems can be found throughout the following 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.

Many of the most common orthopedic problems in cats are included in the following information. Each disease or problem is categorized in this information based on where it is located on the body. The front limb will be covered first, followed by the hind limb. Diseases that affect more than one area of the skeleton will then be covered separately.

 

Problems Found in the Front Limb:

Major orthopedic problems that commonly affect the front limb include fractures, ligament and tendon injuries, growing bone diseases, dislocations, infections, and cancers.
  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 cats because the shoulder is well-protected by surrounding muscles and other tissues. Arthritis can also occur in the shoulder joint.
     
    1. Shoulder joint dislocation can occur as a result of trauma in cats. 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 having the cat wear a special bandage for 2 weeks. Often, however, surgery is a necessary part of the treatment.
       
    2.
  2. Upper leg (humerus): The humerus is the long bone extending from the shoulder to the elbow. Fractures of the humerus are uncommon in cats. 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 figure #1).
     
    Figure 1: Fractured Humerus - This is a fracture in the lower third of the humerus. The white arrow indicates the upper portion of the humerus that connects with the shoulder. 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 can occur, especially following trauma or injury to the joint.
     
    1. 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; 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 cat 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.
  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 cats (see figure #2). 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. Many fractures require surgery, while others can be properly treated with a cast or splint to stabilize the fractured bone(s).
     
    Figure 2: A fractured radius caused by a bullet (white arrow).

     

  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 not uncommon in cats. 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.
     
    1. 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 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. Fusion of the joint, a surgical procedure known as "arthrodesis," is necessary in many cases to restore function.
       
  6. Paw: The feline 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 are rare, but can occur in the nail beds of cats. These nail bed tumors have usually spread to the nail beds from some other location. Life-threatening lung and skin cancers have been reported to spread to multiple nail beds in some cats.

     

Problems Found in the Hind Limb:

Major orthopedic problem categories that commonly affect the hind limb include fractures, ligament and tendon injuries, growing bone diseases, dislocations, infections, and cancers.

  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.

    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 figure #3). 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 result in 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 associated with the passage of bowel movements are important aspects of the treatment plan for many pelvic fracture victims.
       

      Figure 3: 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.

    2. Dislocations of the pelvis can occur 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.

      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.
  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 previously indicated, the medical term for the socket is the acetabulum. The medical term for the ball is merely the "head" of the femur. A variety of conditions can affect the hip joint. Fractures and dislocations are common.
     
    1. Dislocation of the hip joint is a common result of injury to the hind end in cats. 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 through examination by a veterinarian. Confirmation of the dislocation is needed with an x-ray (see figure #4). The x-ray provides important 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 cat 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. A variety of methods are available, depending on the situation.
       
      Figure 4: 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 cat from putting any weight on the leg for up to 2 weeks.
       

    2. Hip dysplasia is far less a problem in cats than it is in dogs, but is reported in the Siamese breed. It appears to be passed in families and can result in crippling lameness. Animals 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.

      Diagnosis of the condition must be made with x-rays and can be treated medically with anti-inflammatory medications. Surgical treatment is the most effective and rewarding treatment available. Total hip replacement can be done in cats as it is in dogs; however, because the condition is seen in cats on a less frequent basis, the surgery is not routinely performed. A less expensive alternative to the total hip replacement surgery is called the femoral head and neck osteotomy (FHO), in which the head and neck of the femur ("ball" of the ball-and-socket) is completely removed and the upper portion of the femur allowed to form another "socket" joint with scar tissues (see figure #5). The surgery is remarkably effective with lightweight animals, and cats tend to do extremely well following this procedure.
       
      Figure 5: Femoral head and neck osteotomy (FHO) - The white arrow shows the location where the head and neck of the femur used to be located. An FHO surgery has been performed.

       

  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 #6-7). Repair is often very difficult and can be very expensive. There are many different ways of repairing a fractured femur, so an orthopedic specialist should be consulted.

     
    Figure 6: Fractured Femur - This is a fracture of the femur just above the bottom or distal end of the bone. The femur is indicated by the white arrow and the black arrow identifies the distal end of the femur or the condyles. To adequately fix this type of fracture, orthopedic surgery is required.

    Figure 7: The black arrow identifies a bone pin placed to repair the fracture shown in figure #6 above.

     

  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 uncommon in cats. When injuries do occur to this joint, they 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. The ligament commonly injured 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) may also occur. Arthritis of the stifle is seen frequently in older patients, usually as a result of some previous injury or problem in the joint. Bone cancers, while rare in cats, may affect the stifle joint area.
     
    1. Cranial cruciate ligament injuries occur uncommonly in cats. 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 cats with a torn CCL are very reluctant to bear any weight on the leg. The lameness can occur suddenly, although many cats 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 can become weak in both stifle joints over time, and when the CCL tears on one side, there is a 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 cats may be more likely to suffer CCL tears for the same reason.

      Diagnosis of CCL tears is made during a detailed exam by a veterinarian. The forward movement of the tibia is detected and helps determine the diagnosis. Some cats may need to be sedated for a thorough examination if they are too tense or in too much pain. 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 cat 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 cat 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 good.
       
    2. Patellar luxation (dislocation of the knee-cap) is another uncommon condition of the stifle joint of cats. This condition is seen most commonly in the Devon Rex and domestic shorthair breeds. The patella usually dislocates towards the inside of the leg (medially) and is generally apparent by the time the animal is 4-6 months old. Both stifle joints are usually affected.

      Trauma to the stifle can also cause dislocation of the patella in an otherwise healthy cat. 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. Some cats will adapt to the patella popping in and out of place as they walk. Some cats 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.
       
    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 of this problem 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 cats. 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 (or vice versa) following a hind limb trauma.

    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).
     
    Figure 8: Fractured Tibia and Fibula - This is a comminuted fracture of the tibia and fibula.

  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 cat’s tail. The Achilles tendon (common calcaneal tendon) attaches to this bone and travels up to the muscles on the back of the cat’s lower limb. The Achilles tendon is rather exposed and can be injured easily. Injuries to the hock joints and bones are common in cats. 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. 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 through 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. 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.
       
  7. Paw: The feline 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 cats. The anatomy and problems associated with the hind paw are identical to the front paw.

 

Problems Found in the Spine:

The feline spine is divided into five sections. First, the cervical or neck portion consists of seven vertebrae (bones that make up the spinal column). The first cervical bone that connects to the base of the skull is called the atlas, and the second cervical bone is called the axis. These two bones are distinct from all other vertebrae in their shape. These bones, along with the other vertebrae of the spine, provide protection for the delicate spinal cord that runs through their center, while at the same time allow for some limited movement in the neck and back. The second section of the feline spine is called the thoracic spine and consists of 13 vertebrae. The 13 ribs connect on either side of the chest to these vertebrae. The third section is called the lumbar spine and consists of seven vertebrae that correspond to the "lower back" in people. Three fused vertebrae make up the unique section of the spine called the sacrum found in the pelvic part of the spine in cats. The final section of the spine is made up of a varying number of vertebrae that become smaller and smaller as the tail tapers. These are called the coccygeal or tail portion of the spine. Vertebrae have projections called processes that extend dorsally (up) and laterally (sides). The processes are termed dorsal spinal processes and lateral spinal processes. They vary in length and shape depending upon where in the spinal column they are located. The dorsal spinal processes are the small ridges that can be felt running the length of the back. These are very useful in helping to count the vertebrae in the spine during examination.

Spinal column injuries can be devastating to an animal because any damage to the delicate spinal cord running through the center of the spine can result in permanent paralysis of portions of the body. Intervertebral disk disease, where the cushion-like disks in between the bones of the spine become deformed, is not commonly seen in cats. Spinal injuries and diseases are more commonly associated with the branch of medicine entitled neurology rather than with orthopedics. The most common type of abnormality associated with the spine in cats is probably the kinked tail, a birth defect which is rather common among some breeds and in some geographical areas. This defect can occur anywhere along the length of the cat’s tail, but is more commonly found toward the very end. Corrective surgery of the problem is usually not effective.

 

Problems Found in the Skull:

The cat skull is extremely complex. It is made up of several bone plates that fuse together as the cat matures, as well as the two paired mandibles or jawbones with their hinges in the back of the lower skull. The central portion of the skull houses the brain and brainstem that are critical to the function of the entire body. Located in front of the brain and on the sides of the face near the nose are open compartments known as sinuses. Hollow openings at the front of the skull house the eyes. The paired mandibles from which the lower teeth grow are connected to each other at the very front part of the skull by a strong ligament and are hinged at the lower back portion of the skull by a joint known as the temporomandibular joint (TMJ). The right and left maxillary bones make up the sides of a cat’s nose and are connected to each other on the bottom by the palatine bone, hard palate, or roof of the mouth. The upper teeth grow from the lower portion of the maxillary bones as it attaches to the hard palate.

Injuries to the skull occur relatively infrequently and are usually associated with blunt trauma, such as an automobile accident. Fractures of any bone in the skull can occur, and depending on what organs or soft tissues are involved, these fractures can be very serious. Head trauma with severe brain or brainstem injury is usually fatal. Most other injuries to the mouth, nose, and face are treatable, although permanent disfigurement can result. Because the many different injuries that can occur to the head, each type of injury must be managed on an individual basis and under the care of a veterinarian.

 

Arthritis:

Arthritis simply means inflammation of a joint. Arthritis can be broken down into several different categories based on the type, location, and cause of joint inflammation. Joints can be freely mobile, partially mobile, or immobile. While inflammation can occur in any joint, the freely mobile joints and, to a lesser extent, the partially mobile joints are those most likely to create problems for the body when they do become inflamed.

The disk joints in between vertebrae in the spine are the most common partially mobile joints where problems develop in the cat. Intervertebral disk disease, where the cushion-like disks in between the bones of the spine become deformed and cause back pain and sometimes paralysis, is not common but does occur. Freely mobile joints include all the joints of the limbs such as the shoulders, elbows, hips, stifles (knees), and all the joints in the paws ("knuckles"). While the specific makeup of each of these joints differs, each contains the same basic structures.

A thin layer of cartilage overlying the bone in each joint provides for frictionless motion. A thick, tough wall called the joint capsule attaches to the bone on all sides and protects the delicate cartilage from damage. The joint capsule also holds in the sticky, clear lubricating fluid that is found inside the joint. This fluid is called synovial fluid and also helps with joint lubrication and frictionless movement.

The three broad categories of arthritis seen in cats include degenerative arthritis, infectious arthritis, and immune-based arthritis. Cats are fortunate in that all three categories are relatively uncommon.
  1. Degenerative joint disease (DJD) is the medical term for the degenerative type of arthritis that occurs in joints. Specific types of DJD have already been discussed, such as hip dysplasia. 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. Genetics, nutrition, previous injury to a joint or nearby structures, infection, and age are some of the more common reasons for developing this type of arthritis. DJD often gradually gets worse with time and may become extremely severe and even crippling.

    Clinical signs of this degenerative arthritis are generally limited to signs of pain: limping, stiffness, reluctance to exercise, protectiveness and even hissing or biting when painful areas are touched. In severe cases, the patient may stumble or fall, 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, cats 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 cat 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. One approach available for some types of arthritis is surgery. Femoral head and neck ostectomy (FHO) for hip dysplasia is a very good example of surgical treatment for arthritis of the hip joint. 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. Many cats 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.

    Anti-inflammatory drugs have been used over the years in the treatment of joint pain and arthritis in cats. Anti-inflammatory drugs come in two types: steroids and non-steroids. Non-steroidal anti-inflammatory drugs (known by the acronym NSAIDs) include aspirin, flunixin meglumine, phenylbutazone, ketoprofen, and meloxicam. NSAIDs are becoming widely recognized as an important part of the treatment of degenerative arthritis. As cats 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 cat to become even less mobile, and the "vicious cycle" mentioned previously continues. Perhaps the greatest benefit of NSAID use in cats with arthritis is the breaking or hindering of this cycle. Use of anti-inflammatory pain killers can keep an arthritic cat 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 cats. In fact, NSAIDs tend to have a rather narrow margin of safety, which means that it is quite easy to create problems with them. Cats are very sensitive to many of these drugs and they should be used with caution and only under the direction of a veterinarian. Acetaminophen (Tylenol), for example, can cause death in cats. NSAIDS which have been used safely in cats include aspirin, phenylbutazone, meloxicam, flunixin, and ketoprofen. Side effects of NSAID use include vomiting, listlessness, loose stools, and hives.

    Steroids are often used for their powerful anti-inflammatory effects in cats, particularly because they tend to be safer than most NSAIDs. Cats are also much less likely to experience side effects such as weight gain from steroid use than other species.
     
  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.
     
    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 caused by a bacterium known as Borrelia burgorferi and is transmitted by ticks of the Ixodes family. Cats have a much greater resistance to Lyme disease infection than do dogs. Rarely, lameness due to Lyme disease infection may occur in cats. Diagnosis is generally made with serology. Treatment is effective with antibiotics, such as amoxicillin or tetracycline. No vaccine currently exists for prevention of Lyme disease in cats. Please see page F498 for additional details on Lyme disease.
       
    3. Ehrlichiosis: Feline ehrlichiosis is caused by several species of small bacteria in the rickettsial family. While the disease in uncommon, it is seen occasionally in the western and midwestern United States. The disease can affect all body systems, with arthritis in multiple joints being a common clinical sign. Fever, loss of body condition, swollen lymph nodes, pneumonia, and blood disorders may also result from feline ehrlichiosis. Diagnosis is based on bloodwork (serology). Treatment with antibiotics is generally very effective. Doxycycline, an antibiotic similar to tetracycline, is the antibiotic of choice for treatment of feline ehrlichiosis.
       
    4. Toxoplasmosis: Toxoplasmosis in cats is caused by a protozoal parasite called Toxoplasma gondii. Generally, young or stressed cats are the most likely to show clinical signs of disease; healthy adult cats may become infected, but do not often show any signs of disease. Infection occurs through ingestion of the parasite in hunted prey such as birds or mice. A form of infective arthritis may occur along with many other clinical signs in affected cats. Diagnosis of toxoplasmosis may be made with bloodwork. Treatment of choice includes antibiotics (clindamycin) and sometimes supportive care. Please see page F836 for additional details.
       
    5. 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 cats. 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 cats. 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.
     
    1. Chronic Feline Progressive Arthritis: This is a disease in cats that is not caused by any type of infection, but may be closely associated with feline leukemia virus (FeLV) infection. About 60% of cats with chronic feline progressive arthritis are also infected with FeLV. The disease occurs in 2 different and distinct forms: Rheumatoid-like progressive arthritis and fibrous ankylosing progressive arthritis. Affected animals may have other clinical signs such as fever, decreased appetite, and weight loss. Each form will be discussed below.
       
      1. Rheumatoid-like progressive arthritis received its name because of its similarity to rheumatoid arthritis in dogs and people. It occurs more commonly in older cats and causes unstable, deformed, and painful joints. Similar to rheumatoid arthritis, radiographs show erosion of the bones in the affected joint where cartilage attaches. Rheumatoid factor, a measurable substance in the bloodstream of dogs and people with rheumatoid arthritis, is not present in cats, however.
         
      2. Fibrous ankylosing progressive arthritis occurs almost exclusively in young male cats. Joints are swollen, painful, and stiff. New bone growth tends to fuse joints and severely restrict their normal range of motion (ankylosis). X-ray films show new bone extending around the joints with loss of bone structure in general inside the joints themselves.

      Diagnosis of both forms of this arthritis is based primarily on history, physical examination, radiographs of the joint, and testing of the joint fluid. Steroid therapy with prednisolone and other immune-suppressing drugs such as azathioprine and cyclophosphamide are the standard treatment. Prognosis is usually guarded to poor because the disease progressively worsens to the point of crippling lameness.
       
    2. Systemic lupus erythematosus (SLE) is an uncommon disease in cats 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 also common.

      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 x-ray films, joint fluid tests, and bloodwork. Testing for antibodies the immune system creates to attack other tissues of the body, also known as "autoantibodies," is used in other species to diagnose SLE, but is very unreliable in cats. 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.
       
    3. Idiopathic polyarthritis is a "catch-all" category where all other unknown causes of multiple joint pain and swelling are placed. Many of the arthritis cases placed into this category appear to result from illness elsewhere in the body or because of reactions to drugs and/or vaccines. 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 may be another cause of idiopathic polyarthritis. Some types of cancer may also lead to inflammation of the joints. 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 resolved, the arthritis will usually go away. Some of these cases respond well to treatment with steroid therapy.

       

Growing Bone Diseases:

Diseases of the developing bones are rare in cats. These diseases can be present at birth or become apparent as the kitten’s skeleton develops. Treatment for these conditions is difficult and often not possible. Examples of some unusual disorders which may be encountered in kittens include the following:
  1. Ectrodactyly: This condition, also known as "split-hand deformity," results from the failure of proper growth or fusion of the bones in the front paw, leading to a deep cleft in the paw itself.
     
  2. Osteogenesis imperfecta: This is a disorder of bone formation at the microscopic level. It frequently results in deformed limbs, fragile bones, and multiple fractures.
     
  3. Multiple cartilaginous exostoses (MCE): This disease causes aggressive swelling and growth of bones near the growth plates. Some of the swellings may become cancerous with time. This disease is listed with growing bone deformities in general; however, it usually develops in cats after the skeleton is already mature. There appears to be a strong correlation between MCE in cats and infection with feline leukemia virus (FeLV). Some references may categorize this disease with feline bone cancers.
     
  4. Radial agenesis: This is a deformity in which the radius never develops at all in the forelimb and the ulna is thicker and more curved than normal (see figure #9).
     
    5. Figure 9: Radial Agenesis - The white arrow with only one point shows the relatively normal radius on one limb. The double headed arrow shows the place where the normal radius should have been on the opposite limb.

     

Neoplasia:

Neoplasia or cancer of the bones is rare in cats. The most common bone cancer diagnosed in cats is osteosarcoma.

  1. Osteosarcoma is the most common bone cancer in cats and arises from bone cells. This type of bone cancer is very aggressive in the bone itself, but does not spread to other parts of the body as commonly as the same type of cancer does in dogs or humans. The hind limbs are affected with osteosarcoma about twice as often as the front limbs. The average age for cats to develop osteosarcoma is around 10 years old; however, it has been reported in cats ranging from 1-18 years.

    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 apparent 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. 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. If there is no evidence of spread of the cancer to other body systems, amputation alone without chemotherapy or other treatment is often very effective and even considered to cure the cancer in some cases.
     
  2. Osteochondroma is a primary bone cancer that arises from cartilage cells within the bone. A form of osteochondroma known as osteochondromatosis can occur in which the cancerous growths may arise from many areas of the skeleton at once. At first the bone growths are usually benign, but with a fairly good chance of becoming malignant and spreading cancer throughout the body. There is a possibility that osteochondromatosis is correlated with feline leukemia virus (FeLV) infections. Diagnosis is made with physical examination, x-rays, and biopsy/histopathology of the growths. Treatment is difficult, especially for osteochondromatosis where the cat may also suffer from FeLV infection.
     
  3. Fibrosarcoma is a cancer arising from connective tissue found throughout the body, including bone tissue. It occurs only rarely in bone and may be difficult to treat. Diagnosis is made by bone biopsy. Little is known about how fibrosarcoma of the bone behaves in cats. Aggressive surgery is considered the best treatment.
     
  4. Hemangiosarcoma is a cancer of blood vessel cells that has been reported as a primary bone cancer in cats. Little is known about how it behaves, and aggressive surgery is recommended. It has been reported to metastasize to other sites of the body.

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. 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:

Broken bones are the most common orthopedic problem encountered in cats. Falls, gunshot injuries, and automobile accidents are all common causes of broken bones in pets. This section will address the basics of dealing with fractured bones in a practical sense for cat owners.

  1. Classification of fractures:
    1. Closed or simple fracture: This is a fracture of a bone where the skin is not broken and no exposure to the outside environment has occurred. The opposite is an open or compound fracture.
       
    2. Open or compound fracture: This is a fracture where exposure with the outside environment has occurred. Examples include gunshot injuries to bones (see figure #2) 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 kittens.
       
    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.
       
    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 cat’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 or injure its owner when it is hurt. 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.

    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 these injuries 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, 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.

     

Infections:

Infections of bones and joints can occur in cats. Infection of bone tissue is called "osteomyelitis" and infection of a joint is called "septic arthritis."

  1. Osteomyelitis is the medical term for bone infections. Bone infections may involve bacteria, fungi, or viruses. Bacteria are responsible for most bone infections seen in cats. Any cat may be affected, and any part of the skeleton may become infected. Bone is typically well-protected and resistant to infection. Open fractures, where the broken ends of the bone penetrate the skin, are perhaps the most common way the infection reaches the bone. Infections may also enter bone tissue following surgery, from infected wounds near the bone, or from the blood supply. Chronic long-term bone infections can result from open fractures and bone surgery. If a fragment of bone dies and is left in the fracture area, new bone may form around it and trap it inside the healed bone. The immune system cannot fight infection inside of dead tissue since it is cut off from the body’s blood supply. Thus the trapped piece of dead bone provides an excellent home for bacteria and leads to long-term infection. Diagnosis of osteomyelitis is usually made with a good history, physical examination, and x-rays (see figure #10). Treatment of osteomyelitis depends upon the situation. Antibiotics and surgery are the primary means of treating bacterial bone infections. Surgery is needed in most cases of long-term osteomyelitis to remove pieces of dead and severely scarred tissue. Antibiotics are provided for several weeks to months.

    Fungal bone infections are very uncommon in the cat, but have been reported. Feline histoplasmosis (Histoplasma capsulatum), a deep fungal infection, is the most common one found in the United States. Other deep fungal infections which affect cats include Cryptococcus neoformans and Blastomyces dermatidis.
     
    Figure 10: Osteomyelitis- The white and black arrows point to areas of osteomyelitis surrounding the end of this femur. There is also a pin in the femur that was used to repair a fracture.

     

  2. Septic arthritis is the term used for an infected joint. Injuries to joints are the most common reason for infection to reach these well-protected areas. Other sources of potential joint infections include injections directly into a joint, surgery, and access through the blood supply. The affected cat is usually in pain, reluctant to bear weight, and may have a fever. The joint may be hot and swollen. Diagnosis of a septic joint is achieved by history, physical examination, x-rays, and by testing a sample of the joint fluid. The joint fluid analysis is the most helpful of the tests in showing the actual infection. Culture and sensitivity (see page D135) may be performed on the fluid, often providing very helpful information for treatment. Septic arthritis is a difficult problem to treat. There is usually extensive and permanent damage done to the delicate tissues of the joint, which results in permanent pain and arthritis even after the infection is gone. Surgery to relieve swelling and pressure, flushing the joint with sterilized fluid, and removing any clumps of infected material is usually the best approach. Sometimes, the joint must be left open and carefully bandaged to allow it to drain. Administration of antibiotics for at least 4 weeks is very important regardless of the surgical approach. The outcome is very questionable, and permanent damage resulting in arthritis of the joint is not uncommon.

Summary: Orthopedic problems are a common occurrence in veterinary medicine. The key to successfully treating these problems is early detection and proper treatment. The pet’s owner plays an essential part in identifying problems early and then seeking the proper medical attention. In general, if lameness in a pet lasts longer than 24 hours, the lameness is getting worse, or there is an obvious injury, veterinary advice should be sought.