Cranial Cruciate Ligament Disease (CCL or Torn ACL) in Dogs

CCL injuries are common in dogs, particularly in large breed dogs. Dogs showing signs of lameness or pain in a hind limb require prompt veterinary care. Virtually all cases of CCL injury or weakness result in osteoarthritis in the joint, a painful condition that can impact quality of life. Prompt assessment of any dog showing signs of lameness, even subtle signs, allows for preventative measures to slow the onset of osteoarthritis. Most cases of CCL injury have a good prognosis with appropriate management.

Both complete and partial CCL tears can occur, and both make the knee joint unstable. Excessive wear from joint instability results in osteoarthritis. Early arthritic changes appear within a few weeks of CCL injury.

The severity of symptoms often correlates with the severity of CCL injury. Complete tears, sudden tears, and tears with meniscal injury often produce the most severe symptoms. Some dogs show only mild, intermittent lameness. Bilateral CCL injury results in lameness affecting both hind limbs.

Damage to the menisci of the knee is very common with CCL injury. Menisci are pieces of cartilage that provide shock absorption for the joint. With CCL injury, the medial meniscus is most commonly damaged. A damaged meniscus produces a clicking sound when the limb is moved, which may be noted by pet owners.

There are several known predisposing factors that increase the risk of a dog getting CCL rupture. Collectively, these predisposing factors are called “CCL disease”, and include:

• Obesity
• Aging
• Poor hind limb conformation, such as being “straight-legged”
• Functional abnormalities of hind limbs, such as patellar luxation
• Breed predisposition
• Genetic inheritance

Large and giant breed dogs are more likely to develop CCL disease, and tend to develop the disease earlier on in life (around 2 years of age).

The most common cause of CCL rupture in dogs is progressive degeneration of the ligaments, eventually leading to ligament failure during activity. The exact cause of ligament degeneration is unknown.

A thorough physical examination is the first step in diagnosing a CCL injury. Specialized examination of the knee joint in flexion and extension helps identify a ligament rupture. These tests can be painful, so sedation is often needed for patient comfort. Other diagnostic tools that are especially helpful for identifying conditions with similar symptoms include:

• X-rays
• Sampling the joint fluid
• Arthroscopy, where a camera is introduced into the joint capsule

While some physical exam findings are suggestive, the only way to visualize the ligament is via advanced diagnostic imaging (CT or MRI). X-rays are not sufficient to image ligaments.

Treatment is dependent on patient factors, such as the severity of the tear, the size of the dog, the degree of inflammation, and whether osteoarthritis has already developed. There is no way to restore stability to the knee without surgery.

A variety of techniques exist for surgical stabilization of the knee following CCL rupture. Little scientific evidence exists to support the use of custom knee braces to stabilize the knee joint in dogs. At best, bracing is only a temporary solution and is not well-suited to young, active dogs.

CCL injuries require significant follow-up care and rehabilitation for a successful outcome. In the immediate postoperative period, activity must be restricted. Crating dogs and going for leashed walks only are helpful methods to reduce activity. Over time, activity levels are increased slowly, with careful monitoring for pain. Professional canine rehabilitation and physical therapy services are often helpful in designing a “return-to-activity” plan for highly active dogs.

All cases of CCL injury are likely to develop osteoarthritis eventually, even when the injury has been surgically repaired. Joint health supplements and therapies help reduce the speed of osteoarthritis onset, extending the useful life of the joint. Weight loss for overweight dogs is also crucial for slowing osteoarthritis.

Most cases of CCL injury have a good prognosis, with lameness improving in 85-90% of cases after treatment. Dogs with CCL injury to one knee are very likely to injure their opposite knee, so dogs must be managed carefully to reduce the risk of traumatic injury.

Developing osteoarthritis in an affected knee is virtually guaranteed, so owners must closely monitor dogs for increasing pain levels or new lamenesses. Note: some human pain medications are toxic to dogs. Never administer medication to a pet without veterinary guidance.

Obesity is a major predisposing factor to CCL injury and rupture, so maintaining dogs at a healthy body weight significantly reduces their risk of injury. Moderate daily activity is also beneficial, as it strengthens the ligaments to counteract degenerative processes.

CCL injury is common, particularly in large breed dogs.

• Anti-inflammatories
• Surgery
• Cage rest
• Exercise restriction