While most of us have heard of hip dysplasia and associate it with many large breeds of dogs, including Golden Retrievers, German Shepherds, and Rottweilers, most of us never think our cat could be a victim. Although the prevalence of clinical disease is low in cats, feline hip dysplasia (FHD) is more common than previously believed. Purebred cats, especially the larger breeds like Persians and Maine Coons, are affected more often than purebred cats, probably due to a smaller gene pool. Scientists are still working out the mode of inheritance, but it is known that the tendency to develop hip dysplasia is an inherited trait involving multiple gene pairs.
A degenerative disorder
The signs of hip dysplasia are not apparent at birth, but develop slowly over time. The hip is a ball-and-socket type joint with the head of the femur (the ball) fitting into a depression in the pelvis called the acetabulum (the socket). When the ball and socket are a poor fit, the result is instability or looseness of the hip joint. The laxity of the hip joint can eventually lead to damage of the joint cartilage and underlying bone. If that happens, painful osteoarthritis may result. Since hind limb lameness can be caused by injury and a number of orthopedic, neurologic, and cardiovascular conditions, these illnesses must be ruled out before a diagnosis of FHD can be made.
It is interesting to note that the majority of cats with hip dysplasia show no signs of the disease. Many times a diagnosis is made after a cat has been x-rayed for another complaint. Cats may have severe degenerative joint disease evident on x-rays, yet show no signs of pain or lameness. The reasons for this remain a mystery to veterinary scientists. James Richards, DVM, director of the Cornell Feline Health Center, suggests that the small size of cats or a peculiarity in the anatomy of the feline hip joint may allow them to tolerate more easily the effects of the disease than do their canine counterparts.
Pain management
Feline hip dysplasia can be treated with non-steroidal, anti-inflammatory drugs. While aspirin is one such drug, aspirin toxicity can be a problem in cats, so owners should never attempt to treat their cats lameness without first consulting their veterinarian. Corticosteroids are sometimes prescribed for reduction of inflammation associated with degenerative joint disease in cats. Although some people champion the use of nontraditional remedies, including neutraceuticals, to aid in joint maintenance and to help control inflammation, the data is only anecdotal and is not substantiated by scientific research.
Richards recommends weight management programs for obese cats because less stress to the hip joint can reduce the cats discomfort. For less severe cases, restricting exercise and limiting access to the outdoors may help.
When pain management is not successful, surgical correction is recommended. The procedure of choice involves removing the femoral head and a portion of the femoral neck so the hip becomes free-floating yet held in place by the surrounding muscles and other tissues. Without bone-on-bone contact within the hip joint, the cat will no longer experience pain. Cats tolerate this surgery very well and usually return to normal function within three to four weeks.
Evaluating abnormalities
Cat breeders would like to know how to predict which individuals in a breeding program will not pass genes for hip dysplasia to future generations, and researchers are currently studying how best to evaluate hip joint confirmation. While it is known that breeding normal toms (male) to normal queens (female) will produce fewer dysplastic kittens, it is not yet possible to predict which individuals have normal hips before they reach breeding age. While these parameters are being determined, the majority of cats that are diagnosed with FHD can be successfully treated and live normal, active lives.
