Quite common among Chihuahuas, bad knees known as Patellar luxation (slipped kneecap), an orthopedic problem, is one of the most common causes of lameness. It’s usually caused by abnormalities in the patella ( a flat, movable bone at the front of the knee) and is a hereditary disorder. Generally, the problem starts when the dog is still young, 6 months or younger, although occasionally an older dog will be affected. Trauma to the knee can also force the patella out of place-something that can happen at any age.
When the patella luxes, the rear lower leg seems to momentarily lock and the dog “skips” for a stride or two; then the leg drops back into place again and everything is fine. Often, the skipping gait occurs while the dog is trotting or directly after he first stands, turns or jumps.
Depending upon how advanced the problem becomes, a dog can experience discomfort, lameness and permanent joint damage, so it’s best not to ignore this condition. A veterinary exam is important to confirm the diagnosis (which is based on a physical exam and radiographs) and to evaluate the severity of the problem as soon as possible.
In mild cases where the patella only very occasionally dislocates and pops right back in the groove, there is no residual lameness, very little discomfort and little or no cumulative or permanent damage to the joint, making treatment unnecessary. You should monitor your pet, however, and have him reevaluated if the luxations become more frequent or the patella stays out of the groove for longer periods of time.
In some cases, the patella luxes more frequently, doesn’t slip back into the groove quickly or the veterinarian determines that the patella pops out too easily. These dogs need surgery to correct the condition and to prevent permanent lameness and joint damage.
In these cases, without treatment, a dog will not get better on his own, and the condition could worsen, causing more pain and greater damage to the joint. The more damage a joint undergoes, the more difficult it is to repair the abnormalities and to achieve complete surgical correction.
To prevent over-exercising, keep your dog on a leash when taken outside to relieve himself and crated at other times. As your dog recovers, leash walks and gradually increased exercise are permitted, per veterinary evaluation. Usually dogs complete their recovery in a couple of months. When patellar luxation is treated promptly, prognosis for a full recovery is usually good.