Hip dysplasia is a fairly uncommon disorder in cats that involves abnormal development and subsequent degeneration of the coxofemoral (hip) joint. It is thought that the immature hip joints of affected cats have a genetic predisposition to subluxate (partially dislocate), causing abnormal forces across the hips, irregularly shaped bones, damaged cartilage, microfractures and, in severe cases, osteoarthritis. It is important for cat owners to recognize the clinical signs of hip dysplasia so that effective treatment options can be pursued as early in the course of the disease as possible. This can be difficult, however, because the signs of hip dysplasia often mimic those of other degenerative disorders.
Symptoms of Hip Dysplasia in Cats
Hip dysplasia is one of the most common skeletal disorders seen clinically in dogs, but is much less common in cats. When it does occur, purebred cats and females are more commonly affected; Maine Coons seem particularly predisposed. Clinical signs tend to show up early, usually between 4 and 12 months of age, although signs of osteoarthritis can first present later in life. The early signs of this disease are caused by looseness in the joints; later signs are related to joint degeneration.
Since hip dysplasia affects the rear limbs, this is where cat owners should look for signs of the disease. The main signs of hip dysplasia are rear lameness characterized by a bunny-hopping or swaying gait, pain or weakness in one or both hind legs, difficulty rising, exercise intolerance, reluctance to run or jump (up the stairs, onto furniture, counters, etc), and sometimes an audible clicking sound coming from the hips when the cat rises or walks (called “crepitus”). Other signs include a narrow hind-end stance, poor pelvic limb conformation and musculature, hypertrophy (enlargement) of the shoulder muscles from overuse and sometimes an arched appearance of the spine caused by the shifting of weight to the forelimbs because the rear end hurts. These signs can be subtle. They can be intermittent or persistent and tend to worsen after activity. Affected cats may seem fine most of the time but be stiff in the morning or after a catnap. Obesity or rapid weight gain can exacerbate the lameness and pain associated with this disease.
Left untreated, hip dysplasia will progress, and the symptoms will become more obvious. Cat owners should be especially aware of signs in kittens as they near maturity, and they should not simply write-off the signs in older cats as a natural decline due to aging. Proper treatment can reduce the discomfort caused by hip dysplasia and allow the cat to remain active and happy.