Cruciate Ligament Injuries in Dogs and Cats

One of the most common causes for hind limb lameness in dogs is a tear in the Cranial Cruciate Ligament (CCL). The CCL (also known as the Anterior Cruciate Ligament or ACL in humans) is a ligament found inside the knee joint. It helps to provide stability in the knee by preventing the tibia (shin bone) from thrusting forward relative to the femur (thigh bone).

What causes cruciate ligament injuries in dogs and cats?

There are 2 types of CCL injuries. An acute rupture or chronic degeneration of the ligament. Acute rupture typically occurs in athletic animals after obvious trauma such as a fall with an awkward landing or sudden changes in direction when a dog (or cat) is running fast. Chronic degeneration is the more common presentation, and these animals are often overweight and have no history of significant trauma, but suddenly start to limp on one of their hind limbs.

How will my veterinarian confirm that my pet has a CCL injury?

When examining an animal with hind limb lameness, the veterinarian pays close attention to the history and the way the animal moves. Upon manipulation of the stifle (knee joint), instability can usually be palpated, the tibia is thrust forward relative to the femur. This is known as a Cranial Drawer Sign and is the classic diagnostic test for confirming CCL rupture. Sometimes if animals are particularly tense during the exam, have very muscular legs, or if the ligament is only partially torn, it can be difficult to appreciate subtle changes. These animals may require sedation to do thorough palpation of the affected leg. Veterinarians will often take radiographs (x-rays) of the affected limb to better assess for arthritic changes in the joints and other possible causes for the lameness. If the veterinarian has a strong suspicion of a CCL tear but is unable to confirm this through palpation, he/she may refer the pet to a specialist to have the knee scoped. The ligament can be directly visualized and assessed.

What treatment options are there for CCL injuries?

Left untreated, cruciate ligament injuries result in ongoing pain and rapid progression of arthritis.

1. Conservative/ non-surgical treatment. This involves use of anti-inflammatory medications and initial strict rest of the animal. Activity levels are gradually increased over a minimum of 16 weeks, and specific rehabilitation exercises can be performed which help strengthen the other supportive structures of the knee. Typically, smaller animals (less than 10 kg) are better candidates for this approach than larger pets. If there is no improvement in gait after 4 weeks, surgical treatment should be considered.

2. Surgical treatment. There are several different surgical techniques for treating CCL injuries. Three of the more popular techniques are the Lateral Fabellar Suture, The Tibial Plateau Leveling Osteotomy (TPLO), and the Tibial Tuberosity Advancement (TTA). The common goal with all techniques is to limit the forward thrusting motion of the tibia when the animal walks as this is what causes the pain and instability which promotes arthritis over time. A pre-surgical consultation with the veterinary surgeon, will include a discussion on these different techniques and which would be most appropriate for your pet.

3. Physiotherapy. Typically, physiotherapy is performed after surgery. The goal is to aid in rehabilitation by strengthening the affected leg, restoring a functional and symmetric gait, aiding in pain relief, and restoring muscle mass to the thigh. Physical therapy modalities include icing the leg, therapeutic laser, specific exercises, and hydrotherapy (underwater treadmill). Your veterinary surgeon will help formulate a specific recommended rehabilitation program for your pet. This may include referral to a facility specializing in physiotherapy.

Prevention of future CCL injuries

Many animals presenting with cruciate tears in one leg will tear the ligament in the other leg at some point in the future. This applies particularly to the more common chronic degenerative type of injuries, where the inherent weakness in the ligament is usually present bilaterally (on both sides). Animals with CCL injuries bear much more weight on the “healthy” leg. The first step in minimizing the risk of the other side tearing is to treat the affected side as promptly as possible and restore a more symmetric gait.
Prevention of obesity and weight reduction in animals that are already overweight is also crucial. Your veterinarian is a great resource for providing information on nutrition and weight loss.

Avoiding exercises that involve rapid running with sudden changes in direction. E.g. chasing balls or jumping for frisbees in dogs with a history of cruciate injury may also reduce the risk of injuring the other leg.

Written by: Dr. Rael Rifkind, Associate Veterinarian