The Agony of a Torn Knee. Why ACL Injuries in Dogs Cause So Much Pain

What is the cranial cruciate ligament in dogs?

The cranial cruciate ligament (CCL) is one of the major ligaments located inside the stifle (knee) joint of dogs (1). It is also sometimes referred to as the anterior cruciate ligament. The CCL crosses diagonally through the inside of the knee joint and connects the femur to the tibia, providing stabilization and preventing excessive internal rotation and hyperextension of the knee (2, 3).

The CCL serves as the primary stabilizer that keeps the knee firmly in place during normal activity. It prevents abnormal side-to-side and twisting movements of the knee joint. When the CCL ruptures or tears, it results in a devastating injury characterized by instability, inflammation, and debilitating lameness in the affected hind leg (1).

The CCL forms an “X” shape with the caudal cruciate ligament inside the knee joint (see diagram below) (3):

diagram showing cranial cruciate ligament in dog knee

In summary, the cranial cruciate ligament is a crucial stabilizing structure located diagonally across the canine knee joint. It prevents abnormal motion and provides shock absorption during activity. A torn CCL causes severe lameness and pain.


How do dogs tear their CCL?

Dogs can tear their cranial cruciate ligament (CCL) through sudden movements, trauma, or degenerative changes in the knee joint.

Sudden stops and turns while running or playing can cause excessive twisting forces on the CCL, leading to partial or complete tears. The CCL keeps the tibia from sliding forward in relation to the femur, so sudden changes in momentum put strain on this important stabilizing ligament.

Trauma from accidents like being hit by a car or falling can also damage the CCL. Blunt force or impact to the knee area may overstretch the ligament beyond its limits.

Degenerative changes in the knee joint are another common cause of CCL tears in dogs. As dogs age, the CCL can weaken and start to fray or deteriorate from chronic wear and tear. Obesity and genetic factors can predispose some breeds like Labradors to degenerative CCL disease.

Any of these mechanisms – sudden movements, trauma, or degeneration – can cause partial or complete ruptures of the cranial cruciate ligament in dogs. This disabling injury requires prompt veterinary attention and treatment.

What are the symptoms of a CCL tear?

photo of dog limping due to acl tear

The most common symptoms of a CCL tear in dogs include:

  • Lameness – Dogs will often limp and favor the injured hind leg (1). This lameness can range from subtle to severe depending on the extent of the injury.
  • Swelling – There may be swelling on the inside of the knee joint or around the tibia just below the knee (2).
  • Abnormal gait – Dogs may have difficulty bearing weight on the affected leg or have a “bunny hop” gait when walking (3).
  • Reluctance to bear weight – Dogs may hold their injured leg up when standing or sitting, and be hesitant to put full weight on it (1).

The degree of lameness and discomfort can wax and wane over time. Some dogs will temporarily improve with rest but the symptoms often return when they are active again (1). Seeking veterinary attention as soon as symptoms appear is important for diagnosis and treatment.




Is a CCL tear painful for dogs?

Yes, a CCL tear can be extremely painful for dogs. The cranial cruciate ligament (CCL) stabilizes the knee joint. When it ruptures, it causes inflammation, instability, and pain in the knee and leg (1).

When the CCL tears, dogs will often vocalize and nip or bite when their injured leg is touched or handled. This is their reaction to the pain and discomfort (2). The intense pain from a CCL rupture comes from both the tearing of the ligament itself, as well as joint instability after the tear. Without the CCL stabilizing the knee, abnormal motions cause inflammation of other knee structures (3).

Dogs may suddenly start limping or holding their hind leg up after a CCL tear. They tend to avoid bearing weight on their injured leg due to the pain. However, some dogs will try to hide or mask the pain at first (3).

A complete CCL rupture is an intensely painful injury for dogs. They require pain medication and sometimes surgery to treat it. With proper treatment and recovery, most dogs can return to normal, pain-free function after a CCL tear.


How is a CCL tear diagnosed?

xray diagnosing acl tear in dog knee

Diagnosing a CCL tear starts with a physical examination by the veterinarian. The vet will check for signs of lameness, swelling, pain, and instability in the knee joint. They will perform orthopedic tests like the tibial thrust test, cranial drawer test, and tibial compression test to check for ligament damage.

The vet may also take X-rays of the knee to look for signs of arthritis and bone changes that can indicate a CCL tear. However, X-rays don’t directly show ligament damage. According to Veterinary Teaching Hospital, the “sensitivity of X-rays for completely torn CCLs is only about 50%.”.

If the physical exam and X-rays are inconclusive, the vet may recommend an MRI. MRI provides a definitive diagnosis by allowing the vet to visually inspect the ligament for tears or rupture (1). It can also help assess the extent of the injury to determine the best treatment approach.

How are CCL tears treated?

Treatment for a CCL tear in dogs usually begins with a period of rest, anti-inflammatory medications, and physical therapy to reduce pain and inflammation while promoting healing of the injured ligament. This approach aims to stabilize the joint and strengthen the surrounding muscles to compensate for the torn ligament. According to the Veterinary Teaching Hospital at Colorado State University, dogs with partial CCL tears may respond well to this conservative management strategy before considering surgery (

If the CCL tear is complete or the dog does not improve with conservative treatment, surgery may be recommended. There are different surgical techniques to repair CCL tears in dogs. Two common procedures are tibial plateau leveling osteotomy (TPLO) and tibial tuberosity advancement (TTA). Both aim to stabilize the stifle joint by altering the biomechanics. According to the University of Illinois Veterinary Teaching Hospital, factors like the dog’s age, size, and activity level help determine the best surgical approach ( The surgeon will advise on the optimal treatment plan for the individual dog.

What is the recovery process after CCL surgery?

dog doing physical therapy after acl surgery

After CCL surgery, dogs need to follow a 6-8 week strict rest period to allow the knee to heal properly. This requires keeping the dog in a crate or small room without furniture when unsupervised. Activity should be restricted to very short leash walks to go to the bathroom. Running, jumping, playing, and climbing stairs should be avoided during this time (source).

Around weeks 2-4, physical therapy starts which includes passive range of motion exercises, massage, cold laser therapy, and other modalities to help strengthen the leg muscles and prevent atrophy. Hydrotherapy such as underwater treadmill walking may be incorporated later in the recovery period. Through weeks 6-8, longer and more frequent leash walks are encouraged along with physical therapy to rebuild muscle tone and stamina (source).

The recovery is very gradual, and dogs usually return to normal activity around 3 months after surgery. Jumping, running, and off-leash activity are carefully added back in under a veterinarian’s guidance to make sure the knee fully heals.

What can be done to prevent CCL tears?

There are several things pet owners can do to help prevent CCL tears in their dogs:

Keep the dog at a healthy weight. According to How to Prevent ACL Tears in Dogs: Six Things You Must Do, extra weight puts additional stress on the knee joints and ligaments, increasing risk of injury. Keeping the dog trim can take pressure off the CCL.

Regular exercise helps strengthen muscles and ligaments around the knee joint, providing more support. Activities like swimming or brisk walking are ideal low-impact exercises.

Joint supplements containing glucosamine and chondroitin may help lubricate and protect the knee joint. Consult a veterinarian to see if these supplements could benefit your dog.

With proper weight management, exercise, and nutrition, owners can help prevent CCL tears and keep their dogs active and healthy.

Long-term prognosis after CCL tear

The long-term prognosis for dogs after surgical repair of a CCL tear is generally good, with most dogs able to return to normal activity levels. According to one study, over 85-90% of dogs have substantial improvement after CCL surgery (

However, arthritis is a common long-term complication that can develop over time after a CCL tear. The instability and joint changes that occur with a CCL rupture can lead to progressive arthritis in the knee joint. While this may result in some stiffness or difficulty with demanding activities like jumping, most dogs can live comfortably with well-managed arthritis.

There is also a risk of a CCL tear occurring in the dog’s other knee. Studies show around 30-40% of dogs tear the CCL in their opposite knee at some point, especially larger breed dogs. This highlights the importance of physical therapy and joint supplements after CCL surgery to help prevent reinjury.

While a CCL tear is a major injury, the prognosis for return to normal or near-normal function is good with proper surgical treatment, rehabilitation, and management. Most dogs can enjoy a high quality of life after recovering from a CCL repair.

When to seek veterinary help

If your dog is showing signs of a potential CCL tear, it’s important to seek veterinary care as soon as possible. Some key signs that warrant an urgent veterinary visit include:

– Lameness lasting more than 48 hours (

– Obvious swelling in the knee joint

– Abnormal gait or reluctance to bear weight on the affected leg

Your veterinarian can perform exams and diagnostic tests to determine if your dog has a partial or complete CCL tear. The sooner this injury is diagnosed and treated, the better the outcome will be for your dog’s recovery. Delaying veterinary care risks further damage to the knee joint. If your dog shows any signs of an ACL injury, don’t wait – call your vet right away to schedule an appointment. Acting quickly can help get your dog back on the road to healing.

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