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Anterior/Cranial Cruciate Ligament Rupture
Knee Anatomy

The knee is a joint that is formed by three bones: Femur (the long bone extending down from the hip); Tibia (the bone between the knee and ankle); and Patella (the kneecap). These bon es arejoined together by a number of ligaments. These ligaments prevent the ends of the femur and tibia from moving back and forth across each other. The ACL (anterior cruciate ligament) in humans is equivalent to the CCL (cranial cruciate ligament) in animals. You will find that your veterinarian may use both terms to describe this injury.

Rupture of the anteriorcranial cruciate ligament (ACL/CCL)
When the anterior (cranial) cruciate ligament ruptures (is torn), the joint becomes unstable and the femur and tibia can move back and forth across each other. The anterior cruciate ligament is commonly torn due to an acute trauma, however the tear can happen without severe trauma, especially in obese animals. Usually the ACL/CCL is weakened due to slight trauma, then progressivley gets weaker until it fully ruptures. Dogs with a degenerating ACL/CCL will generally have the condition in both knees.

Symptoms of a ruptured cruciate ligament

A pet with a ruptured ACL will general become suddenly lame on the affected leg, and usually will not bear weight. Swelling can be noted and the pet is painful. With pain management, some pets will begin to use the leg again, but the lameness and pain return if the ligament is not surgically repaired.

Diagnosis of a ruptured cruciate ligament

The diagnosis of a ruptured cruciate ligament is made through observing abnormal movement of the joint through palpation and diagnostic radiography. With palpation, the veterinarian can elicit a 'drawer sign'. It is called that because the movement of the femur in relation to the tibia is similar to pulling and pushing in the drawer of a cabinet. Many dogs with a ruptured cruciate ligament will have swelling on the inside aspect of the knee, and this is called a medial buttress. Radiographs are commonly performed to better assess the amount of arthritis that may be present.

Treatment of a ruptured cruciate ligament

Surgery is indicated with a complete ACL tear, especially in large dogs. There are several methods of repairing the knee joint, those of which should be discussed with your veterinarian and the surgeon.

Fascial Graft/Lateral Suture Stabilization (LSS)

The fascial graft is performed by using a portion of the patellar tendon or other tissue to reconstruct

the damaged ligament. The lateral suture technique involves placing a polypropylene line around the outside of the knee joint to stabilize it from moving front to back.

Tibial plateau leveling osteotomy (TPLO)

In this procedure, a portion of the tibia is cut, moved, and reattached to a different portion of the tibia using plates and screws. By changing the conformation of the tibia, the joint is stabilized. This is a technically difficult surgery but it has shown to produce excellent results, often with less arthritis.

Tibial tuberosity advancement (TTA)

The objective of the TTA is to advance the tibial tuberosity, which changes the angle of the patellar tendon to neutralize the tibiofemoral shear force during weight bearing. By neutralizing the shear forces in the stifle caused by a ruptured or weakened ACL, the joint becomes more stable without compromising joint congruency. (Kowaleski, et. al.)

Tight Rope

This procedure was developed to provide a minimally invasive method for extrascapular stabilization of the CCL. This technique does not require bone cutting like the TPLO and TTA. Instead, it uses small drill holes in the femur and tibia to pass a synthetic ligament-like biomaterial through a small incision. This provides bone to bone stabilization during healing. (www.innovativeanimalproducts.com)


If the dog's exercise is restricted as instructed, and overweight dogs return to normal body weight, the prognosis is good. Depending on the amount of injury to the knee and length of time between the injury and correction of the problem, degenerative joint disease may occur as the pet ages.