Dear Lisa: My seven-year-old yellow lab is beginning to limp on his right rear leg. He doesn’t want to put any weight on it. Several years ago he had an injury to his left knee which ruptured his cruciate ligament. He had surgery to fix it. Is it possible that the other knee is starting to go as well?  – Needing a New Knee

Dear Needing: It is not only possible that the other knee is going but highly likely. Statistically, a dog is 80 percent likely to rupture the ligament in the other leg within one year. So your dog dodged the odds with several years between possible ruptures. It appears that your dog is going to suffer from both types of cruciate ligament rupture: the acute (or injury) onset and the chronic (or age-related degeneration) onset.

The acute onset of Anterior Cruciate Ligament (ACL) 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. Examples may include a dog running and falling in hole or stopping suddenly to twist and catch a Frisbee®.

The chronic onset is attributed to among other things; age, usually between five- to seven-years-old and the normal degeneration of fibers in the knee that may include partial tears. Other factors include obesity or carrying excessive weight, 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 which puts extra strain on the ligaments. Another contributing factor to having the opposite ACL rupture is that surgery does not fix the knee joint but merely stabilizes it. The knee is not at good as new, although normal function may return, and therefore puts an added burden on the other healthy knee.   

How can you tell if your dog’s ACL is failing? With a sudden tear or rupture a dog will usually yelp and then hold its leg up very high and not be able to put any weight on it. Dogs with this injury can’t bear weight on the knee without collapsing. There will be obvious signs of pain. Diagnosis can be done by your vet with a manipulation of the femur and tibia in a certain way to show instability. Also, sometimes a clicking noise can heard. With a gradual onset the dog will slowly show symptoms, such as limping and weight-bearing avoidance.

To understand how these injuries happen, it is important to understand just how unstable the knee joint is. There are no interlocking bones to keep this joint together such as the hip. The two main bones at the knee (or stifle joint) is the femur (or thigh bone) and tibia (or shin bone) and they are joined by ligaments and a crescent-shaped piece of fibrous cartilage called a meniscus.

Once the ACL is torn or ruptured, arthritis begins to set in within a few days as the knee joint is no longer able to function and bones start rubbing together. Surgery is the best treatment to stabilize the joint. In surgery, a specialist will most likely use artificial ligaments (sometimes heavy gauge nylon or fishing line) versus grafts, to replace the ACL. If there is damage to the meniscus or cartilage it too is removed. For some wonderful photos and further explanations of the surgery go to www.thepetcenter.com/sur/knee.htm.

The biggest threat to ruptured ACL patients is the early onset of arthritis. Surgeons report they find arthritic changes in dogs which have waited several weeks between injury and surgery. The odds are against the dog if surgery is not done, especially in larger dogs. A study showed that less than 20 percent of dogs over 30 pounds showed normal joint function after four years. And the risk of arthritis to your dog is very great if the surgery is not performed soon after the injury. 

The surgery is expensive (approximately $1,000) but the pain and accelerated rate of arthritis to your dog is inevitable without surgery. Most dogs recover with normal function within six to eight weeks especially with carefully controlled exercise, physical therapy and supplements such as Glucosamine and Chondrotin to help promote healing and tissue repair.  

            

Lisa Peterson, a breeder and exhibitor of Norwegian Elkhounds, is a Delegate to the American Kennel Club and the owner of Peterson Pet Sitting. Ask Lisa questions at elvemel@aol.com or P.O. Box 197, Newtown, CT 06470.