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A cranial cruciate ligament rupture (CCL) is the tearing of an important ligament in the stifle (knee) joint. This is the classic "football player's injury." A tear in this ligament results in joint instability, pain, and limping or lameness. The fragments of the torn ligament retract deeper into the joint, do not heal together, and cannot be repaired. If the injury is not treated, damage to surrounding tissues and degenerative joint disease (arthritis) will result.

The femur (thigh bone) and the tibia and fibula (shin bones) meet to form the stifle joint. The cranial cruciate ligament (CCL) is located inside the joint, and attaches to the femur, runs across the stifle joint, and attaches to the tibia. The CCL holds the tibia in place and prevents internal rotation and hyper- (over) extension of the knee. Rupture of the cranial cruciate ligament allows the femur to slide back and forth over the tibia as the knee has lost its stability.

Cranial cruciate ligament (CCL) rupture can occur in both dogs and cats, however it occurs more frequently in dogs. It is one of the most common orthopedic injuries in dogs and is the most common cause of arthritis in the knee joint. CCL rupture occurs in dogs of all sizes, but is most prevalent in large and giant breeds. Dogs 5-7 years old are most likely to have chronic onset (degeneration and rupture usually from aging). Acute onset (a tear caused by injury) is most common in dogs under 4 years old.

Acute rupture of the cranial cruciate ligament (CCL) is caused by sudden, severe twisting of the knee. This injury usually occurs when an animal steps in a hole while running or turns quickly with its paw firmly planted on the ground. The twisting motion causes the ligament to stretch or rotate excessively and partially or completely rupture. The meniscus (impact cushion of the joint) is often damaged as well.

Chronic rupture occurs after the ligament has degenerated with age. The fibers weaken and partially tear, the joint becomes unstable, and degenerative joint disease develops. A partially torn CCL eventually tears completely.

  • Age of the animal
  • Pre-existing arthritis
  • Traumatic injury to the knee joint
  • Large or giant breed dog
  • Overweight dog

Lameness in the hind leg is the most common sign of cranial cruciate ligament rupture. The animal may be unable to bear weight or may limp significantly. Lameness occurs immediately after the injury.

Other symptoms of CCL rupture include the following:

  • Crepitus (crackling/crunching noise of bones rubbing against each other)
  • Decreased range of motion in the knee
  • Sitting with the hind leg extended
  • Pain when knee joint is touched
  • Resistance to exercise 
  • Swelling around the knee
  • Thick, firm feel of the knee joint
  • Standing with the animal's weight shifted to one side of body

Once the ligament is ruptured, movement of the misaligned joint causes further damage, inflammation, pain, and eventually arthritis. If the meniscus is torn, a pop or snap may be heard when the animal walks.

Diagnosis is confirmed with a physical examination of the knee joint. The cranial drawer sign is definitive for diagnosing CCL rupture. The drawer sign occurs when the femur is tightly held and the tibia is pulled forward. If the tibia moves substantially there has been a partial tear or rupture. Heavy sedation may be necessary to perform this test because pain from a ruptured CCL can be severe, and thigh muscle tension can restrict the motion of the joint. Radiography (x-ray) may suggest, but cannot confirm, a partial tear or a complete rupture.  X-rays do not show ligaments or other soft tissues, but can show fractures and signs of arthritis as well as the presence of excess joint fluid.

Treatment can be conservative which is least expensive option. Conservative treatments include weight loss to reduce stress on the joint, rest or confinement to alleviate inflammation, and medication for pain control. Conservative treatment may be appropriate for older dogs and those with other serious health problems, or can be used for cats and dogs that weigh less than 25 pounds. Lameness may continue until surgical repair is performed. The treatment of choice for large dogs is surgical repair. Surgery is performed on healthy animals, and requires an experienced surgeon and owner compliance for proper healing.  Arthritis often progresses regardless of treatment.

Surgery is the preferred treatment in dogs over 25 pounds. If surgical intervention takes place within a few weeks of the injury, the result is a very good return to function. Surgery will slow, but not stop, the development of degenerative joint disease.

Multiple surgical procedures are available, all with comparable results. The surgeon's expertise and the size and type of the dog determine the surgical technique used to replace the function of the torn ligament.

In all procedures, the joint first is opened and the remnants of the CCL are removed. The meniscus is assessed and if damaged, it is removed. The joint is flushed and closed. The type of repair used at the Roslyn-Greenvale Veterinary Group involves the placement of a heavy suture (thick stitches) across the joint as shown in the picture above. Scar tissue will eventually form, providing additional joint stability.

After surgery, the animal should rest until the joint is fully healed to avoid re-injury. The joint may become unstable or the surgical repair may fail and another surgery may be required if exercise and activity restriction is not enforced.

Up to 40% of animals that have a ruptured CCL will sustain a similar injury to the other knee joint within 18 months of surgery. 

Pain medication will be necessary after surgery. The medications most commonly used include a narcotic pain patch immediately after surgery combined with non-steroidal anti-inflammatories. Animals must be confined with strictly limited activity for several weeks after surgery. Their diet should be modified to prevent excess weight gain. Exercise may be gradually increased after several follow-up examinations. Normal activity usually resumes within 2-3 months after surgery.

Prognosis is good to excellent with full function restored in most cases. The presence and extent of arthritis at the time of surgery negatively affects the long-term prognosis.

Animals may experience stiffness and lameness for months to years after surgery, especially if degenerative joint disease progresses. Vigorous exercise and long periods of rest may worsen lameness.

If your dog is exhibiting any signs of cranial cruciate ligament rupture please call 516-621-4010 to schedule an appointment for an evaluation today.

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