Another of the common joint ailments that affect dogs, hip dysplasia is a disorder that is widely misunderstood. As with all human types of arthritis, some information is known, but many factors about the problem aren't yet fully understood.
In normal, healthy dogs, the hip joint attaches the hind leg to the body, and consists of a ball-and-socket construction. The ball portion is located at the head of the femur, or thigh bone, while the socket is attached to the pelvis. In a normal joint, the ball rotates freely within the socket, and the spot where the two bones actually connect (the articular surface), is cushioned by spongy cartilage. The bones also are held together with a ligament and the joint capsule, a strong band of connective tissue which surrounds the dog's two leg bones, adding stability.
Hip dysplasia develops when the joint develops abnormally in a young dog, usually one that was born with normal hips. One or both hip joints may be affected. Genetic factors, aging, disease and injury can cause a loosening of the joints, muscles, cartilage and/or connective tissues. Whatever the cause, the leg bones are moved further apart, weakening the joint capsule and ligament, and making the entire joint unstable. Over time, the damage leads to arthritis in the affected joint, resulting in pain and limited movement.
Puppies as young as five months can develop hip dysplasia and osteoarthritis; yet it's more common in older dogs. In most cases the animal will be in obvious pain or discomfort during and after vigorous exercise, and eventually during normal daily activities. Affected dogs also usually walk with a stiff or otherwise irregular gait, or appear to "bunny hop" as they run. As the dysplasia progresses, most dogs voluntarily limit their activity, losing muscle tone as a result. If no treatment is prescribed, the dog may be unable to walk within one to two years.
Many owners consider these symptoms to be a normal sign of aging in their pet. X-rays and a physical exam can provide a definitive diagnosis. There are several types of surgery which may be performed, depending upon the dog's age, physical condition and the type of damage the hips have experienced. Anti-inflammatory and pain relief medications also may be prescribed, along with supplements like glucosamine and chondroitin, which have been proven to help re-grow cartilage. Pet owners also will need to monitor their dog's weight and exercise carefully, as well as provide a warm sleeping space. Massage and physical therapy have proven to be effective adjunct treatments, as well, especially when osteoarthritis has developed.
In the canine world, large and giant breed dogs are more likely to develop hip dysplasia, although it does appear occasionally in medium-sized and smaller dogs. Purebred dogs are affected more often than mixed breeds; when cases occur in mixed-breed dogs, it's usually because the dog is a cross between two breeds that are prone to the disease. Commonly affected breeds are: Border Collies, German Shepherds, Golden Retrievers, Great Danes, Rottweilers and Saint Bernards.