Among the many problems that can develop in a dog's hip joints is a condition known as Legg-Perthe's Disease, a disabling ailment that causes deterioration and flattening of the hip joint.
In most dogs, the disease develops when the animal is between four and eight months old. Lameness can come on suddenly or else develop gradually over six to eight weeks. During this period of time the muscles begin to atrophy, giving the impression that the dog has one limb shorter than the others. There also will be noticeable restricted movement in the animal's joints. When the leg muscles become weakened through atrophy, it slows down the animal's recovery.
LPD occurs in small dogs more than in large ones. It is particularly prevalent in the miniature and toy breeds, as well as Yorkshire Terriers and West Highland White Terriers. The disease first causes the affected animal to lose blood supply to the femur (thigh bone). When this happens, bone tissue also is lost, causing the neck of the femur to collapse and flatten. Normally the neck of the femur attaches the ball, or head, of the femur to the rest of the thigh bone. When this neck collapses, the head of the femur moves into an improper position, and over time becomes deformed. The end result is joint deformity, pain and lameness that worsen over time. In most cases only one hip is affected, but the disease can strike both hips in the same animal.
Legg-Perthe's disease affects male and female dogs equally. It's not yet known why the original loss of blood to the femur occurs, but the disease is congenital, meaning it can be passed from parents to pups.
Dogs with LPD are diagnosed through X-rays. Since the deterioration occurs slowly, X-rays may need to be repeated every three to four weeks in order to confirm the diagnosis. The condition is treated through surgery, in which the damaged femoral head and neck are removed. Once the damaged bone is removed, the ligaments that stretch across the hip joint will strengthen and form a false joint. Recovery from the procedure is slow; many dogs take up to a year to regain full use of the affected limb. In general, smaller dogs recover more readily and completely than larger dogs, and many dogs may be left with a slight limp or other gait abnormality. Most, though, recover and go on to lead a high quality of life. The best results are seen in animals that undergo surgery before any serious muscle deterioration occurs.
There is no way to prevent Legg-Perthe's disease, other than to avoid breeding animals that have the disease or are known carriers. Any dogs you plan to breed should have their hips X-rayed and certified as clear when the animal is one year old. In this way, any mildly affected dogs will be identified before they pass the genes on to another generation. This is important, since mild cases of LPD typically go unnoticed while the animal is growing up. You can have your dog's X-rays examined and certified as clear of LPD through organizations such as the Orthopedic Foundation for Animals and the Institute for Genetic Disease Control.