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

The cranial cruciate ligament is a strand of connective tissue in the leg that stabilizes the knee joint. In humans, this ligament is known as the ACL, so many people incorrectly call CCL disease or a torn CCL or ACL in cats. Cats with CCL disease experience pain and loss of function of the affected leg.

Prognosis is good, most cats return to the equivalent levels of exercise seen before the onset of CCL disease with surgical therapy, and usually have a faster recovery than those treated conservatively.

Cats with suspected CCL disease benefit from prompt veterinary attention.

Cranial cruciate ligament (CCL) disease is uncommon in cats. However, it is more common in old and obese, or young, active cats. Symptoms vary depending on the underlying disease process.

Traumatic rupture of the ligament presents with sudden onset, severe lameness which gradually improves whereas degenerative CCL disease results in mild lameness which gradually worsens over time as the ligament frays. Degenerative versions of CCL disease sometimes rupture acutely during the degenerative process known as ‘acute on chronic’ CCL disease.

Predisposing factors for degenerative CCL disease include

• Obesity
• Increasing age
• Steepness of the angle of the knee joint, known as the tibial plateau angle (TPA).

CCL disease is either traumatic or degenerative.

Traumatic CCL disease involves acute injury such as:

• Falling from a height
• Car accident
• Injury to other structures in the leg such as the collateral ligaments or the menisci (the shock absorbers of the knee joint)

Degenerative CCL disease involves the slow fraying of the fibers of the ligament.

In long term, chronic cases, the affected limb often develops arthritis.

Diagnosis involves:

• Physical examination
• X-rays
• MRI
• CT scans
• Microscopic examination of joint fluid

There are two treatment options: conservative and surgical.

Conservative management includes:

• Pain relief
• Exercise restriction
• Weight management
• Physiotherapy

Surgical treatment includes:

• Stabilization of the knee joint using a synthetic ligament
• Altering the standing angle of the joint to stabilize the knee without the cranial cruciate ligament

Surgery is the only way to restabilize the knee.

Prognosis varies but most cases have a good outcome where the majority of cats return to the same level of exercise as prior to the disease with treatment.

Outcome depends on the severity of disease, treatment option, and damage to other structures in the affected leg, such as meniscal tears.

Long term stabilization of the knee relies on thickening and strengthening of the joint capsule, a fibrous sheath which surrounds the joint, known as fibrosis.Complete CCL ruptures, and concurrent damage to the knee joint, results in significant instability of the joint which delays fibrosis and leads to prolonged recovery times. Complete ruptures that are treated conservatively take up to 6 months to move without lameness, whereas the same cases treated surgically usually recover within 3 months.

Partial tears are less common in cats and normally result in more subtle lameness. Treatment options are the same but sometimes recover more quickly with both surgical and conservative management.

All cases of CCL disease develop subsequent osteoarthritis; there is some evidence that osteoarthritis develops faster in cats that are treated conservatively.

Prevention is challenging in cats as many cases are traumatic and are not preventable. Degenerative forms of CCL disease may be prevented through weight management and not breeding cats with suspected degenerative disease as there may be an inherited component.

CCL disease is uncommon in cats

• Pain relief
• Exercise restriction
• Weight management
• Physiotherapy
• Surgical treatment