Cruciate Ligament Tears

One of the most common causes of hind limb lameness in dogs is a tear of an important ligament in the knee, called the cruciate ligament. In people, it is commonly referred to as the ACL. Cats can tear it also, but it is far more common in dogs. In people, it usually happens as the result of an injury, often sports related. However, in dogs, usually the ligament is just weakening over time until it tears one day when the dog jumps off the couch or runs after a squirrel.

            The problem usually presents as a sudden onset of lameness where the dog cannot bear hardly any weight on its hind leg. Over the next two days, it improves mildly to the point that they can put their foot down but still not fully bear weight on the limb. That is typically as good as it gets.

            We diagnose cruciate tears on physical examination but often need to have the patient sedated to be able to conclusively do so. We like to take x-rays to see if there are also any hip problems and to assess the amount of arthritis. Rarely, osteosarcoma can develop in the knee and cause the cruciate ligament to rupture, so we will take x-rays to look for that also.

            I used to do a lot of surgery to fix cruciate tears but now almost all of them respond to physiotherapy! We love to have a non-surgical option for our patients! However, some dogs don’t respond to physiotherapy and the surgical option is then pursued. For smaller dogs, I have done many extracapsular repairs myself. For the large patients, we get a specialist in to do a TTA or TPLO done or refer them to a specialist at their surgical facility.

            Even with therapy, there will be some arthritis that develops. But without therapy, most dogs will have considerable painful arthritis in their knees for the rest of their lives.