Cranial cruciate ligament (CCL) rupture is the tearing of an important ligament in the stifle joint (knee), resulting in partial or complete joint instability, pain, and lameness. If the injury is not treated, lameness frequently persists, and degenerative joint disease often results. In certain cases, a pad of cartilage in the stifle, called a meniscus, can also concurrently tear. If the meniscus is torn, a pop or snap may be heard when the patient walks.
CCL rupture occurs much more frequently in dogs than in cats. It is one of the most common orthopedic injuries in dogs and is the most common cause of degenerative joint disease in the stifle joint. CCL rupture occurs in dogs of all sizes but is more prevalent in large and giant breeds. Typically, it is a condition seen in middle-aged dogs, although it can be seen at any age.
Cause and Clinical Signs
CCL rupture can be acute or chronic. An acute rupture of the CCL is caused by sudden, severe twisting of the ligament. The injury usually occurs when the pet steps in a hole while running or turns with its paw remaining planted. In chronic cases, the ligament degenerates prematurely and eventually tears completely.
Lameness in the hind leg is the most common sign of CCL rupture. The pet may be unable to bear weight on the affected limb or may limp. Lameness occurs immediately after the injury and may subside somewhat after several weeks but is likely to return.
The diagnosis is usually made on physical examination. The knee is palpated for evidence of pain or instability. Anesthesia may be necessary to move the limb to the extent needed to make the diagnosis because pain from a ruptured CCL can be severe, and muscle tension can restrict the motion of the joint.
Radiography (x-rays) may suggest, but cannot confirm, a partial tear or a complete rupture. Unfortunately, ligament tears do not show up on radiographs; however, we will typically see other signs of degenerative joint disease that are secondary to the tear.
Arthroscopy, a minimally invasive procedure performed with a fiber-optic camera, is occasionally used to confirm a diagnosis. The canine stifle joint is too small to allow for definitive surgical correction to be performed through arthroscopy.
The goal of treatment is to alleviate pain as well as increase use and mobility of the affected knee. Conservative therapy and surgical therapy have been advocated for the treatment of CCL rupture. Conservative treatment consists of weight control, rest for 4 to 8 weeks, and medication to relieve pain and inflammation. Short walks on a leash are permitted. Unfortunately, conservative management is typically not very effective in dogs that weigh more than 30 pounds.
Surgery is the preferred treatment in dogs over 30 pounds. In most cases, it will restore function to the affected limb. Surgery will slow, but not stop, arthritis from developing in the affected joint.
Many techniques have been described for the repair of CCL rupture in dogs; however, there are three techniques that are used most commonly:
• MRIT (Modified Retinacular Imbrication Technique)-One or more bands of monofilament nylon are placed around the stifle joint to restore stability.
• TPLO (Tibial Plateau Leveling Osteotomy)-The angle at the top of the tibia is changed to prevent the tibia from sliding forward.
• TTA (Tibial Tubercle Advancement)-The patellar ligament, or knee cap ligament, is advanced forward to prevent the femur from sliding backwards on the tibia.
The type of technique chosen to replace the function of the torn ligament depends on the size, type, and age of the dog and its activity level. In all procedures, the joint is first opened and the remnants of the CCL are removed. The meniscus is assessed and if damaged, it is removed. In restoring stability, it is important to understand that when the CCL ruptures, the tibia slides forward relative to the femur.
After surgery, the patient should rest until the joint is fully healed to avoid re-injury. Up to 40% of dogs will develop a similar rupture in the other hind limb.
We also recommend several rehabilitation exercises in order to improve function and prevent muscle atrophy. The following links are provided to give instruction on these exercises if they have been recommended for your pet.