Cranial Cruciate Ligament (CCL) Rupture Symptoms & Treatment Options for Dogs and Cats

Cranial cruciate ligament (CCL) rupture is the tearing of an important ligament in the stifle joint (knee), resulting in partial or complete joint instability, pain, and lameness. Torn ligaments retract, do not heal, and cannot be repaired completely. If the injury is not treated, damage to connective tissues and degenerative joint disease often results.

The CCL attaches to the femur (thigh bone), runs across the stifle joint, and attaches to the tibia (shin bone). The CCL holds the tibia in place and prevents internal rotation and hyperextension. The meniscus (fibrocartilage located between the femur and tibia) absorbs impact and provides a gliding surface between the femur and tibial plateau. The medial meniscus can become torn when the knee is unstable from a CCL rupture.

CCL rupture is one of the most common orthopedic injuries in dogs and is the most common cause of degenerative joint disease in the stifle joint. CCL rupture occurs in dogs of all sizes, but is most prevalent in large and giant breeds. CCL rupture can occur in cats, as well, but with less frequency.

Chronic onset (degeneration and rupture usually from aging) occurs in 80% of cases and occurs in dogs 5 to 7 years old. Acute onset (tear caused by injury) is most common in dogs under 4 years old. Chronic rupture occurs after the ligament has degenerated with age. The fibers weaken and partially tear, the joint becomes unstable, and degenerative joint disease develops. A partially torn CCL eventually tears completely.

Symptoms of CCL rupture include crepitus (crackling noise of bones rubbing against each other), decreased range of motion, hind leg extended when sitting (sit sign), pain when stifle joint is touched, reluctance to exercise, restricted mobility or extension, stiffness after exercise, swelling, thick or firm feel of joint and weight shifted to one side of body when standing. Once the ligament is ruptured, movement of the misaligned joint causes further damage, inflammation, pain, and eventually degenerative joint disease. If the meniscus is torn, a pop or snap may be heard when the animal walks.

Diagnosis includes a clinical examination and medical history (information about lameness and injury). The veterinarian tests the joint’s range of motion. The cranial drawer sign is definitive for diagnosing CCL rupture. Anesthesia may be necessary to move the limb to the extent needed because pain from a ruptured CCL can be severe, and muscle tension can restrict the motion of the joint. Radiography (x-ray) may suggest, but cannot confirm, a partial tear or a complete rupture

Treatment of CCL rupture is aimed at the alleviation of pain and increased use and mobility. Conservative treatment (weight control, rest, medication) is often combined with surgery, but it can be used alone for dogs that weigh less than 25 pounds and for cats. However, lameness may continue until surgical repair and a more rapid progression of arthritis is expected.

Surgery is the preferred treatment in dogs over 25 pounds. It may not completely restore function, but does provide good results if performed within a few weeks of the injury. Surgery will slow, but not stop, degenerative joint disease (arthritis). Several surgical procedures are available with good. The surgeon’s expertise and the size and type of the dog determine the surgical technique used to replace the function of the torn ligament.

In the extracapsular imbrication technique, a heavy nylon suture is placed across the joint, beginning at the outside aspect of the femur and circling the tibial crest – in essence, replacing the CCL. In the weeks after surgery, scar tissue forms, providing additional joint stability.

In the tibial plateau leveling osteotomy (TPLO), the stifle joint’s biomechanics are altered to make the CCL no longer necessary for stability of the joint. Surgically changing the angle of the tibial plateau prevents the femur from sliding off of the tibia. Many dogs can move the limb within a week and recovery time is usually short. This complex surgery reportedly has good results in dogs that weigh more than 35 pounds.

In either procedure, the meniscus is assessed and if damaged, it is removed.

After surgery, the pet must be confined and activity strictly limited for several weeks. The diet should be modified to prevent weight gain. The pet is initially allowed outside only to eliminate. Subsequent exercise may be gradually increased after a 6-week follow-up. Normal activity usually resumes 2-3 months after surgery.

Up to 15% of patients require additional surgery to repair damage to meniscus. Up to 40% of dogs have rupture the CCL in the other hind leg within 18 months after surgery. If the CCL in the other stifle joint is ruptured, surgery is postponed until the repaired joint recovers fully. Prognosis is good to excellent with full function restored in over half of the cases. The presence of degenerative joint disease negatively affects the long-term prognosis.

Pets may continue to experience stiffness and lameness after vigorous exercise, especially if advanced degenerative joint disease is present.

Additional information regarding Cranial Cruciate Ligament Rupture (and other common surgical disorders in dogs and cats) can be found on the website of the American College of Veterinary Surgeons.