Cranial Cruciate Ligament Tear (CrCL)

Cranial cruciate ligament tears are the most common cause of lameness in dogs. The Cranial Cruciate Ligament (CrCL) is one of the main stabilizers of the knee joint. When the CrCL tears, it allows the bones of the knee to shift abnormally during weight bearing. This leads to pain, limping, and arthritis. The CrCL is the equivalent structure to the ACL in people.

A CrCL tear will typically cause acute-onset hind leg limping. Frequently dogs will hold their affected leg up while walking or will “toe-touch” when walking slowly. Lameness becomes worse after certain activities or after periods of rest. Limping may also be mild and intermittent, especially if a partial tear is present.

Diagnosing a CrCL tear involves an orthopedic examination, x-rays, and evaluation of the knee at the time of surgery. Orthopedic examination will identify discomfort while manipulating the knee, swelling inside the joint (effusion), thickening around the joint (medial buttress), and instability (cranial drawer and cranial tibial thrust) if a complete tear has developed. X-rays of the knee will identify swelling inside the joint, arthritis, and sometimes instability. X-rays will also help eliminate other potential causes of back leg limping and knee pain. Finally, a CrCL tear is confirmed at the time of surgery either arthroscopically or by performing an arthrotomy (opening the joint for visual inspection).

Arthroscopy is a minimally invasive technique to evaluate the inside of a joint. Similar to joint surgery in people, it involves using a camera and instruments through small incisions (portals). Arthroscopy improves visualization inside the joint and greatly decreases the size of the incision, compared to the more traditional open technique (arthrotomy). Many dogs will also tear the meniscus with a CrCL tear. Arthroscopy has been shown to be a more accurate and precise method of properly diagnosing meniscal tears and it offers the advantage of treating meniscal tears minimally invasively. This is the same technique used to treat people with a torn meniscus.

There have been numerous surgeries invented to treat CrCL tears in dogs. To date, there is not a perfect procedure to stabilize the knee joint, however good functional outcomes are well documented following surgery. In people, an ACL tear is treated by replacing the ACL. Similar techniques have been performed and studied in dogs; however high rates of failure and complications have been documented. As a result, ACL replacement techniques are not currently recommended for our pets. The most commonly performed surgeries to treat CrCL tears in dogs include: Tibial plateau leveling osteotomy (TPLO), tibial tuberosity advancement (TTA), lateral suture techniques, and the TightRope technique.