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Dear AKC: My seven-year-old yellow Labrador Retriever is beginning to limp on his right rear leg. He doesn't want to put any weight on it. About two years ago, he had surgery on his left knee to fix a ruptured cruciate ligament due to an injury. Is it possible the other knee will need surgery too?– Knee-Jerk Reaction in Reno

Dear Knee-Jerk: One of my dogs had three Anterior Cruciate Ligament (ACL) surgeries. While working with a skilled surgeon, I learned that statistically, a dog is 80 percent likely to rupture the ligament in the other leg within one year. So far your dog has dodged the odds. Your dog suffered from the acute (or injury) onset and my dog suffered from the chronic (or age-related degeneration) onset of ACL rupture. It only took my dog 6 months to have her other ligament rupture, requiring a trip back to the surgeon.

My vet told me that the acute onset of rupture usually affects dogs under four-years-old and is triggered by a sudden, twisting motion of the ligament causing it to tear or completely snap in half. The chronic onset can be attributed to many things, including age, obesity, being a giant or large breed, a spayed female, having poor muscle condition around the ligament or a structural abnormality such as being bow-legged or straight-legged. Another contributing factor to having the opposite ACL rupture is that surgery does not fix the other knee joint but merely stabilizes it. The knee is not at good as new, although normal function may return, it therefore puts an added burden on the other healthy knee.

Vet's Diagnosis Needed

How can you tell if your dog's ACL is failing? With my dog, she had a sudden rupture, yelped in pain, and then held her leg up. She was not able to put any weight on it. Once the ACL is torn or ruptured, arthritis can set in within a few days as the knee joint is no longer able to function and bones start rubbing together.

My dog's surgeon reported that surgery is the best treatment to stabilize the joint, especially in larger, heavier dogs. He said he routinely finds arthritic changes in dogs which have waited several weeks between injury and surgery. My dog recovered normal function within eight weeks of surgery using a carefully controlled regime of exercise, physical therapy and supplements. Take your dog to the vet as soon as possible to get a correct diagnosis.