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ANATOMY

There are two cruciate ligaments in the canine knee joint, the cranial and caudal cruciate ligaments (CrCL & CaCL). The same ligaments are present in human knees except they are called anterior and posterior cruciate ligaments (ACL & PCL). The CrCL (or ACL) is most commonly injured in both dogs and people and results in knee instability. Two cartilage pads called menisci are also found within each knee (medial and lateral meniscus).

 

WHY DID THE CrCL RUPTURE?

In contrast to people, where ACL rupture is almost always caused by trauma, most dogs suffer from a slowly progressive CrCL degeneration. The resulting weakened CrCL can rupture with minimal trauma. We do not yet fully understand the cause of CrCL rupture. Because CrCL degeneration is occurring in both knees, there is a 20-40% chance that dogs will rupture the CrCL in their opposite knee sometime in the future.

 

CLINICAL SIGNS

Lameness is the most common symptom seen with CrCL rupture. It can vary from a mild, intermittent to a non-weight bearing lameness. Some patients will have a clicking or popping noise in the knee during walking. This may indicated meniscal damage.

 

DIAGNOSIS

CrCL rupture is diagnosed by palpation (feeling the knee) and radiographs (X-rays). Most dogs with CrCL rupture have instability in the knee called cranial drawer. Dogs that are very tense or those having chronic or partial CrCL rupture may have little cranial drawer detected. Radiographs are helpful in these patients and often show osteoarthritis and joint swelling. 

 

SURGERY

Surgical stabilization of the knee is recommended for treatment of dogs with CrCL rupture. While many different procedures have been developed over the years, we offer two surgical options here at SVS. With either technique, the meniscus is evaluated. If the meniscus is intact, a meniscal release is performed to minimize the chance of later tearing. If the meniscus is torn, it is removed and fibrocartilage (scar tissue) will later fill the void and replace the function of the damaged meniscus.

 

 

 

The TPLO was developed about 20 years ago to treat CrCL rupture in large breed dogs. It has become the most commonly performed surgery for treatment of CrCL rupture in dogs, and is the procedure that we recommend for large breed dogs. Dogs that have a TPLO performed tend to use the affected limb sooner than dogs that have other procedures performed. There is also growing evidence that dogs that have a TPLO develop less osteoarthritis than dogs with other procedures. 

 

The procedure produces functional stability of the knee by changing the tibial platau slope. This is done by sawing the top of the tibia (osteotomy) and leveling thetibial plateau to prevent cranial tibial thrust during weight bearing. The saw cut is stabilized with a special bone plate and screws that hold the bone while it heals. Normally, the intact CrCL stops cranial tibial thrus, a force resulting from tibial compression generated during weight bearing. After TPLO, weight bearing that will cause caudal tibial thrust is stopped by the caudal curciate ligament. Changing the tibial plateau slope stabilized the knee during weight bearing.

 

After surgery, a soft-padded bandage will be put on the operated leg. The bandage will be removed before your dog goes home. Your dog’s activity must be restricted to leash walks for a period of 8 weeks after surgery. Restricting your dog’s activity level plays a major role in the success of the surgery.

 

A recheck examination with radiographs will be required at 8 weeks after surgery to assess bone healing. A second recheck visit is sometimes needed if the bone heals slowly.

 

The following complications have been reported: infection, inflammation of the patellar ligament, fracture of the tibial tuberosity, breakage or loosening of the bone plate or screws, delayed healing of the osteotomy site, rupture of the caudal cruciate ligament, and post-operative meniscal injury. Some of these complications require additional surgery. These complications have been very uncommon at SVS.

 

The TPLO is the most commonly performed procedure to treat large breed dogs with CrCL rupture because dogs treated with a TPLO have a better functional outcome and decreased development of osteoarthritis than dogs treated with “traditional” methods. Depending upon the severity of osteoarthritis and cartilage damage that your dog already had, s/he may show signs of lameness early in the morning, after heavy exercise, or on cold days. Dogs with severe osteoarthritis may have a persistent lameness.

 

 

To prevent cranial tibial thrust, the knee is stabilized using strong nylon sutures placed on the outside of the joint capsule. These sutures are anchored at the back of the femur and then pass through a hole drilled in the tibial tuberosity (see picture..?). Eventually scar tissue aligns itself around the nylon sutures and ultimately it is this scar tissue that holds the knee stable (since the suture will eventually stretchor break).

 

After surgery, a soft-padded bandage will be put on the operated leg. The bandage will be removed before your dog goes home. Your dog’s activity must be restricted to leash walks for a period of 8 weeks after surgery. Restricting your dog’s activity level plays a major role in the success of the surgery. Physical therapy exercises can be done to help expedite your dog’s recovery. It generally takes up to 3-4 months before your dog will be fully recovered and using the leg well.

 

A recheck examination is usually not required unless complications develop.

 

The following complications have been documented: irritation, breakage and/or infection of the heavy nylon stabilizing sutures, and post-operative damage to the meniscus. Some of these complications require additional surgery.

 

The prognosis following surgery is generally good. About 90% of the dogs will go on to have normal pet function. However, they will have slightly decreased range-of-motion (stiffness) and the osteoarthritis will still progress (although much slower than without surgery). Depending upon the degree of osteoarthritis and the presence of cartilage erosions, your dog may show signs of lameness early in the morning, after heavy exercise, or on cold days. Dogs with severe osteoarthritis may have a persistent lameness.