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Anterior Cruciate Ligament (ACL)  

ACL (Anterior Cruciate Ligament) surgery in dogs is a commonly done surgical procedure in veterinary practice. When the anterior cruciate ligament is torn or stretched, instead of moving like a hinge, the knee joint will actually make a sliding motion. This abnormal motion and instability creates trauma within the joint that leads to wearing of cartilage, increased synovial fluid production and inflammation. Clarification: For this discussion, the term 'Anterior' may be used interchangably with 'Cranial', which is more correct in a discussion of an animal.  

How Does an Injury Happen?

A torn cruciate ligament can occur in any dog if just the right (or wrong) forces impact the knee joint. Most commonly seen in larger breeds of dogs and in dogs that are overweight, the ACL surgical procedure does not actually repair the torn ligament but rather replaces the ligament with artificial material that takes over the function of the Anterior Cruciate Ligament. In the case presented here, nylon strands of 80 pound tensile strength are utilized to restabilize the knee (stifle) joint.

The veterinarian may tell the dogs' owners something like, "The dog has a torn Anterior Cruciate Ligament, and the best way to get him back to full function would be to do a surgical procedure where an artificial ligament is placed along the side of the knee joint. We don't try to fix the torn ligament because that particular one just won't heal properly. So we fool the knee into thinking that there is a ligament. After a few weeks of confinement, and then controlled activity, the fibrous connective tissue buildup along the artificial strands implanted along the knee joint stabilize the joint during activity. Then your dog can begin using the leg properly."

Eventually, Degenerative Joint Disease (DJD) is the result.

NZYMES Treats and Granules

Dog SurgeryIMPORTANT: Should your pet require any type of muscular-skeletal repair work or surgery, we recommend to DOUBLE THE DAILY USAGE of NZYMES Antioxidant Treats or Granules. Begin 3-4 days before the procedure and continue the double usage for 2 weeks to 30 days after. In most cases we have found that the time needed for recovery is reduced significantly; often as much as 50%.


Stifle (knee) joint disorders are a frequent cause of hind limb lameness in dogs. The stifle joint in dogs is similar to the human knee - it represents the articulation between the femur (thigh bone) and tibia/fibula (shin bones). The primary ligamentous support of the stifle joint is provided by the femorotibial ligaments. Ligaments are bands up of strong tough fibrous connective tissues that join bones together. The femorotibial ligaments include the medial and lateral collateral ligaments and the cranial and caudal cruciate ligaments. The collateral ligaments join with and provide some external support to each side of the joint capsule. The cruciate ligaments are present inside the joint and help to stabilize the joint. The function of the cranial cruciate ligament is to constrain the stifle joint so as to limit internal rotation and cranial (forward) displacement of the tibia relative to the femur (cranial drawer motion) and to prevent hyperextension of the joint.

Cranial Cruciate Ligament Rupture

Dog and cat knees are similar to humans. For example, knees have five ligaments, two menisci, a knee cap, and joint cartilage. The ligament most commonly affected in dog and cat knees - the cranial (anterior) cruciate ligament - is the same ligament (ACL) most commonly damaged in professional athletes. Dogs and cats usually tear this ligament when out running around, or sometimes when landing wrong after a jump.

The cranial cruciate ligament is a large, strong ligament located within the knee joint. It is not actually a single structure, but is actually made up of a bundle of individual fibers tightly bound together to form the ligament. Most of the time when the ligament is injured, it is completely torn in half. Sometimes though, only a portion of the ligament will tear. Though only a portion of the ligament may be torn, the whole ligament is damaged; it also cannot 'heal' or repair itself.  For sake of reference, this type of injury is also the most frequent form of leg injury occuring in people who snow ski.

When a cranial cruciate ligament is torn, it causes sudden pain and often results in the pet holding its leg up. It also causes an instability in the knee joint. The pet may put the leg down and start using it within a day or so, but will continue to limp for several weeks. Normally, at the end of several weeks, the initial pain subsides and the pet is willing to use its leg more; however, the joint remains unstable. Every time the animal puts weight on the leg, the tibia (shin bone) slides forward in relationship to the femur (thigh bone). This abnormal motion causes wear and tear on the joint cartilage, causing pain and leading to arthritis. This motion can also put excessive stress on the menisci (C shaped pieces of cartilage within the knee joint), causing damage or tearing.

Since there is no option of self-healing, surgery is the only corrective measure for cranial cruciate ligament injuries. Many surgical procedures have been tried on people and animals during the last 60 years; however, most orthopaedic surgeons agree that the procedures are not as successful as they would like. Knees that suffer this injury are never completely normal even after surgery is performed. Surgery does, though, stabilize the knee, allowing it to regain normal motion and thereby reducing the formation of arthritis. Surgery has been and remains the treatment of choice for this injury. If surgery is not performed, progressive arthritis will occur and the lameness will worsen with time.

There are many different ways to stabilize a knee with a cruciate ligament injury. The procedure usually recommeded here is a modification of the DeAngelis procedure, which involves placing either heavy gauge suture material or orthopaedic wire from the back of the femur, across the joint, and to the front of the tibia. This will tighten up the joint and stabilize it. Over time, scar tissue will lay down around the suture or wire to form a structure which mimics the function of the normal cranial cruciate ligament. The majority of animals will regain normal or near normal use of their leg after the surgery and after a period of rehabilitation. Strict limitation of activity is necessary after the surgery for a period of six weeks so that the animal does not over stress the repair before the scar tissue has formed. Total rehabilitation time, as in people, can be several months.