Hip dysplasia is a congenital disease that, in its more severe form, can eventually cause lameness and painful arthritis of the joints. It is caused by a combination of genetic and environmental factors. It can be found in many animals and, rarely, humans, but is common in many dog breeds, particularly the larger breeds.
In the normal anatomy of the hip joint, the thigh bone (femur) joins the hip in the hip joint, specifically the caput ossis femoris. The almost spherical end of the femur articulates with the hip bone acetabulum, a partly cartilaginous mold into which the caput neatly fits. It is important that the weight of the body is carried on the bony part of the acetabulum, not on the cartilage part, because otherwise the caput can glide out of the acetabulum, which is very painful. Such a condition also may lead to maladaptation of the respective bones and poor articulation of the joint. In dogs, the problem almost always appears by the time the dog is 18 months old. The defect can be anywhere from mild to severely crippling. It can cause severe osteoarthritis eventually.
Luxating patella is a condition where the kneecap (patella) moves out of its normal position. Luxating patella is one of the most common knee joint abnormalities of dogs, but it is only occasionally seen in cats. It may affect one or both of the knees. In some cases it moves (luxates) towards the inside of the knee, and in other cases it luxates towards the outside of the knee. Luxation to the inside of the knee is the most common form seen; it is most commonly seen in the small or miniature breeds of dogs such as Poodles, Maltese, Yorkies, and Chihuahuas. Luxations towards the outside of the knee are seen less frequently. It can be present in many breeds, but is seen especially in Newfoundlands.
There are four grades of patellar luxation:
- Grade I- the kneecap can be manually luxated but the kneecap returns to its normal position when the pressure is released.
- Grade II- the kneecap can spontaneously luxate out of position with just normal movement of the knee.
- Grade III- the kneecap remains luxated most of the time but can be manually reduced into the normal position.
- Grade IV- the patella is permanently luxated and can not be manually repositioned
Dogs frequently start with a Grade I or Grade II and worsen over time to a Grade III or IV. Many people are not aware their pet is affected, but a luxating patella can cause pain. Owners may see the pet limp on a rear leg, or they may see them shake a rear leg to try to snap the kneecap back into place.
A serious consequence of patellar luxation is that it predisposes the dog to a rupture of a ligament inside the knee called the anterior cruciate ligament (ACL). ACL ruptures are very painful, at least initially, and usually the dog doesn’t bear weight on the affected leg. Surgery is indicated for any case that is causing lameness or pain. Owners may also elect corrective surgery as a way to prevent an ACL.
The rupture of the cruciate ligament is the most common knee injury in the dog.
This injury has two common presentations. One is the young athletic dog playing roughly who acutely ruptures the ligament and is non-weight bearing on the affected hind leg. The second presentation is the older, overweight dog with weakened or partially torn ligaments that rupture with a slight misstep. In this patient the lameness may be acute or there may be more subtle chronic lameness related to prolonged joint instability.
Your veterinarian will perform an orthopedic exam and take radiographs (x-rays) in order to diagnose this injury. The orthopedic exam involves an analysis of the gait, examination of the joint for swelling and/or pain and the presence of “drawer movement” (the presence of forward instability of the knee joint). Sedation is often required to do an adequate evaluation of the knee, especially in large dogs. Sedation prevents the pet from tensing the muscles and temporarily stabilizing the joint and preventing the demonstration of the drawer sign. Radiographs confirm inflammatory changes in the joint and establish the level of osteoarthritic changes present.
Surgical repair is recommended in most cases to stabilize the joint and prevent further osteoarthritic changes secondary to the joint instability. There are three primary types of surgical repair: intracapsular, extracapsular, and tibial plateau leveling osteotomy (TPLO).The type of surgical repair will be determined by the size, age and activity level of the pet as well as the degree of osteoarthritis already present in the joint. The recovery time and recommendation for physical therapy will depend on the type of surgical repair performed.
The most common type of arthritis is osteoarthritis which can be due to wear and tear on joints from over use, aging, injury, or from an unstable joint such as which occurs with a ruptured ACL (anterior cruciate ligament) in the knee.
The chronic form of this disease is called degenerative joint disease (DJD). It is estimated that 20% of dogs older than one year of age have some form of DJD. One study showed that 90% of cats over 12 years of age had evidence of DJD on x-rays.
Other causes of the inflammation can be infectious. Septic arthritis is caused by a bacterial or fungal infection. Lyme disease or Ehrlichia infection can also cause arthritis. Auto-immune diseases, or what is now called immune- mediated diseases, such as Lupus can cause swollen, painful, inflamed joints. More rarely, tumors can cause arthritis.
Treatment for arthritis should be directed to the inciting cause if possible. Surgery may be needed to stabilize a joint. DJD may be treated with NSAID’s, pain medication such as Tramadol, cartilage protective agents such as glucosamine or Adequan, acupuncture, or as a last resort, steroids. NSAID’s (non-steroidal anti-inflammatory drugs) have many types. In general, it is recommended to use NSAID’s developed for pets, and not ones made for use in people as those are highly likely to cause ulcers in dogs, and most NSAID’s can’t be used in cats.