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Cranial Cruciate Disease – Part 1

By April Guille, DVM, DACVS - Portland Veterinary Specialists | Jun 01, 2018

A cruciate injury is the most common orthopedic issue we deal with in our canine companions. Chances are that any dog with sudden rear leg lameness has a ruptured cranial cruciate ligament rather than something else. There are two cruciate ligaments in the knee (stifle) joint. The cranial and caudal cruciate ligaments form an X in the joint, and it is the cranial cruciate ligament (CCL) that is most commonly injured. The vast majority of these injuries do not come from a traumatic event, but rather from a combination of genetics, conformation of the limbs, and environmental factors (ie. conditioning, obesity) that lead to a degradation of the ligament. At some point, the strands of the ligament start to fail, resulting in the rupture. In fact, a significant number of dogs that tear the CCL ligament in one knee will go on to tear the other side.

The CCL prevents excessive forward motion of the tibia in relationship to the femur as well as internal rotation. With a complete tear this forward instability, called cranial drawer, can be felt on physical exam in a relaxed dog. Cranial drawer is only possible if the cruciate ligament is torn. Sometimes the ligament will only have a partial tear which prevents this sign on physical exam. Your veterinarian may have a strong suspicion of a cruciate tear, however, based on radiographs (X-rays) of the stifle joint. While the ligament itself cannot be seen on radiographs, signs such as joint swelling and arthritis are common findings and raise a high index of suspicion for an underlying cruciate tear.

The cruciate ligaments do not heal well on their own. A partial tear will almost always progress to a complete tear of the ligament. There are also two C shaped cartilage “cushions” in the joint, called the menisci, which can become damaged due to the joint instability, causing further inflammation and pain. The abnormal wear between the joints and the meniscal cartilage causes changes resulting in chronic pain and loss of joint motion.

People will often ask if surgery is necessary for a CCL tear. Surgery allows evaluation and removal of the torn ligament, assessment of the menisci to remove any damage, and stabilizes the joint. The goal is to stabilize the knee, removing a source of discomfort, and minimizing the progression of osteoarthritis within the joint. Conservative therapy may be considered in dogs weighing < 30 pounds although very little objective data has been generated to support conservative therapy. One small study of 86 dogs showed that dogs weighing < 30 pounds had their lameness resolved in up to 86% of the cases at 4 months. Conservative therapy consists of cage rest, restricted activity, weight control, and appropriate nonsteroidal anti-inflammatory (NSAID) medications. Only 19% of dogs weighing > 30 pounds regained near normal function. This kind of joint disease is substantially more difficult for a large breed dog to bear, though all sized dogs will ultimately show degenerative changes (osteoarthritis) in the joint. Typically, after several weeks from the time of the acute injury, the dog may appear to get better but is not likely to become permanently normal. Any dog not responding to conservative therapy by 4 months should have surgery performed. Dogs with meniscal tears should also have surgery, as conservative therapy cannot address this debilitating issue.

There are multiple surgeries that are available for a torn cruciate ligament. Some of the most common ones include: lateral fabellar stabilization, a tibial plateau leveling osteotomy (TPLO), and a tibial tuberosity advancement (TTA). In next month’s article, we will go into more detail about the surgical options and post-operative recovery.