The rupture of the cruciate ligament is the most common knee injury in the dog. It occurs when one of the cruciate ligaments (most often the cranial cruciate ligament) becomes torn-either completely or partially.The cruciate ligaments’ function is to stabilize the knee so the joint cannot move in a forward or backwards sliding motion.
Cruciate ligament tears have two common presentations. One is the young athletic dog playing roughly, who suddenly ruptures the ligament and won’t put weight on the affected hind leg. The second presentation is the older, overweight dog with weakened or partially torn ligaments that rupture with a slight misstep. In this patient the lameness may be sudden or a more subtle chronic limp that gets worse.
In order to diagnose this injury, we will perform an orthopedic exam and likely take radiographs (x-rays) of the affected leg. The orthopedic exam involves an analysis of the gait, examination of the joint for swelling and/or pain and the presence of “drawer movement” (the presence of forward instability of the knee joint). Sedation is often required to do an adequate evaluation of the knee, especially in large dogs. Sedation prevents the pet from tensing the muscles and temporarily stabilizing the joint and preventing the demonstration of the drawer sign. Sedation also helps to alleviate any discomfort on your pet during this examination. Radiographs confirm inflammatory changes in the joint and establish the level of existing arthritic changes in the joint.
Surgical repair is recommended in the majority of cruciate ligament tears. Surgery helps to stabilize the joint and seeks to prevent extensive further damage to the joint due to lingering instability. Instability within the joint causes pain, inflammation and ultimately arthritis formation.