CRANIAL CRUCIATE LIGAMENT (CCL) INJURIES
WHAT IS THE CRANIAL CRUCIATE LIGAMENT (CCL)?
The cranial cruciate ligament (CCL) is the most important stabilizing ligament of the knee. It connects the femur to the tibia and consists of two closely associated bands. It is synonymous with the anterior cruciate ligament (ACL) in people.
WHAT IS THE FUNCTION OF THE CCL?
The primary function of the CCL is to keep the knee stable and maintain the normal anatomic position of the femur relative to the tibia so that the cartilage surfaces contact each other normally during weight bearing.
WHAT HAPPENS WHEN THE CCL TEARS?
When the CCL tears, the knee becomes unstable. This creates stress and damage to the cartilage surfaces of the femur and tibia. Instability of the knee will cause the joint capsule (synovium) to become inflamed (synovitis) which will lead to fluid build-up and arthritis within the knee cavity.
WHAT CAUSES THE CCL TO TEAR?
There are multiple factors that contribute to tearing of the CCL. These include natural degeneration of ligament fibers, mechanical stress, osteoarthritis, genetics, conformation of the knee, and breed predispositions. Most CCL tears are chronic in nature. Sudden tears due to trauma to the knee are much less common. The initial tear is spontaneous and usually happens anywhere from a few months to up to a year before a limp is observed. During the partial tear phase, inflammation begins to develop in the knee and an intermittent limp may be seen. As the ligament tear progresses and the knee becomes more unstable, limping becomes more consistent or severe. Once the ligament tears completely, your dog will exhibit increased pain and a noticeable limp.
IS THIS A PAINFUL CONDITION BECAUSE MY DOG DOES NOT SEEM TO BE IN PAIN?
Yes, a tear of the CCL is very painful and your dog will often cry out and begin limping when the ligament completely tears. Most dogs will still try to walk on the leg with a torn CCL, but they will exhibit a limp. If your dog is limping, it means they are experiencing pain.
HOW IS A CCL TEAR DIAGNOSED?
Cranial cruciate ligament injuries are usually diagnosed with a combination of lameness evaluation/gait analysis, palpation, and radiographic evaluation of the knee. Dogs who have sustained a CCL tear will walk with a limp and shift weight off the leg while standing. Most dogs will be unable to fully bend the knee, so they will sit to the side with their knee and leg extended. If knee instability is palpated, a CCL tear likely exists. Partial CCL tears can be more difficult to diagnose with palpation alone as instability may not be as apparent. Radiographs are performed to evaluate for fluid build-up in the knee (effusion), arthritic changes, and abnormal positioning of the femur relative to the tibia. If any of these abnormalities are seen on radiographs, a CCL tear is the most likely diagnosis. Advanced imaging (MRI) is not usually needed. In some cases, arthroscopic evaluation of the knee can be helpful if other diagnostic tests are not conclusive.
WHAT IS THE BEST TREATMENT FOR A CCL INJURY?
Surgical stabilization of the knee is the best treatment for CCL injuries. This is the only way to eliminate the instability in the knee. Surgical stabilization has a high success rate and has been shown to improve overall function and mobility, reduce pain and inflammation, and slow the progression of osteoarthritis. Without surgery, most dogs will have a persistent limp and develop debilitating osteoarthritis in the knee. There are a number of different knee stabilization procedures that can be performed. At VOMC, the Tibial Plateau Leveling Osteotomy (TPLO) is the recommended procedure for knee stabilization. This procedure provides superior knee stability and control of osteoarthritis and will help your dog regain good leg function and mobility.
IS MY DOG A CANDIDATE FOR KNEE STABILIZATION SURGERY?
Most dogs are suitable candidates for knee stabilization surgery. Even older dogs can greatly benefit from knee stabilization. There is not a set criteria as to which dogs should have surgery or not; however, dogs that are overweight or obese and have underlying health or neurologic conditions may not be good candidates for surgery.
WHAT IS THE RECOVERY TIME FOLLOWING KNEE STABILIZATION SURGERY?
The initial recovery period following surgery will depend on the procedure performed, but usually ranges from 10 to 16 weeks. Long term recovery can be up to 6 months.
ARE THERE NONSURGICAL TREATMENTS AVAILABLE FOR CCL INJURIES?
Surgical stabilization is the ideal treatment for a CCL injury; however, if surgery cannot be pursued or if your pet is not a good surgical candidate, an aggressive nonsurgical treatment protocol should be initiated. The primary goals of nonsurgical treatment of a CCL injury are to reduce pain and inflammation in the knee, keep the cartilage in the knee as healthy as possible, minimize muscle atrophy (shrinkage) in order to maintain strength, maximize range of motion of the knee, maintain a good body condition, and reduce stress on the other joints. We will provide a comprehensive medical treatment and rehabilitation/conditioning protocol for your pet.
WOULD MY DOG BENEFIT FROM A KNEE BRACE?
We do not recommend using a knee brace as they have not been shown to provide adequate stability for the knee. It is difficult to find a brace that fits and most dogs will not tolerate them for an extended period of time.
IS THERE A CHANCE THAT A CCL TEAR WILL DEVELOP IN THE OTHER KNEE?
Yes, up to 60% of dogs will develop a CCL tear in the other knee. Certain breeds (i.e boxers, Staffordshire terriers, Pit Bulls, Labrador retrievers, Rottweilers) are at an increased risk. On average, most dogs will develop a CCL tear in the other knee 8 months after stabilization of the first knee. Dogs that sustain a CCL tear in both knees in a short period of time will have difficulty walking and supporting there back end. If this occurs, surgical stabilization of both knees is required.
WILL MY DOG BE BACK TO NORMAL AFTER SURGERY?
Following surgical stabilization of the knee, most dogs will regain excellent function of their leg and be able to return to their normal level of activity. Dogs that have more advanced osteoarthritis in their knee, will still show periods of soreness and periodic limping. These dogs will benefit from a long term medical protocol for osteoarthritis that is designed to help slow the progression of osteoarthritis, reduce pain and inflammation, and keep the cartilage in the knee as healthy as possible. If your dog has been diagnosed with chronic knee osteoarthritis, we will provide a long term treatment protocol that will help keep your pet as comfortable as possible and maximize their mobility.