Health: Hip dysplasia

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There may be few more joyous sights than a dog running free, unable to stop as the thrill of tearing around a yard overtakes him. It's this joy that hip dysplasia robs from our dogs, and from us as we watch them age and struggle with their own limitations.

Hip dysplasia is the leading cause of lameness in the rear legs of dogs, especially in large breeds such as Newfoundlands, Saint Bernards, Chesapeake Bay Retrievers, and German Shepherds. It's estimated that 20 to 40 percent of large-breed dogs are afflicted. Even more heartbreaking, this genetic condition can onset from birth, rendering some very young dogs lame. For others, it's a long road toward less and less mobility. But for many dogs there are ways to treat or prevent--or at least lessen the impact of--hip dysplasia.

Causes

The design, structure, and functionality of the canine hip are all strikingly similar to that of a human. The hip is a ball-and-socket joint: the ball is the round head of the femur (thighbone) and the acetabulum (socket) is the concave indentation of the pelvis. In a normal hip, the smooth, rounded head of the femur fits deeply and snugly into the acetabulum. Durable ligaments allow for a wide range of motion and collectively hold the joint together.

In a dysplastic hip, the head of the femur fits loosely or--depending upon the severity of the condition--it may be entirely dislocated from the socket. The bone separating from the joint causes friction and, as the condition worsens, painful arthritis.

Symptoms