Cruciate Ligament Rupture

We have recently dealt with a variety of dogs at the vet clinic who have had their cruciate repaired.  There are a number of our clients who do not fully understand what a ruptured cruciate ligament is so hopefully this information will help.
The knee is a complex joint stabilized by a number of ligaments. The cranial cruciate ligament is one of the most common knee ligaments to be injured or ruptured. The cranial cruciate ligament functions to limit internal rotation and cranial (forward) displacement of the tibia (lower leg bone) in relation to the femur (thigh bone) when the knee is bent. When the ligament is torn or ruptured, the sliding back and forth of these bones cause pain, lameness and instability.

Rupture of the cranial cruciate ligament can occur from acute trauma (severe twisting of the knee) or degenerative causes (chronic weakening of the ligament). Factors involved in degeneration of the ligament are aging, conformational abnormalities, sedentary life style, obesity and immune mediated arthritis. In cats, cranial cruciate rupture is usually due to trauma.

Partially torn cruciates account for 25-30% of knee lameness. The medial meniscus (cartilage in the knee joint) is also damaged/torn in 50% of the cases with a ruptured cruciate ligament.

Diagnosis is based upon physical exam with demonstration of “cranial drawer sign” where the tibia is moved forward in relation to the femur. However, absence of a cranial drawer sign does not rule out rupture. This can be seen with chronic tears, if the dog is exhibiting severe pain, heavily muscled dogs, or anxious patients who are not sedated. If a torn cruciate is suspected in a dog without a cranial drawer sign, your veterinarian will recommend sedation and radiographs (x-rays). The x-rays are not diagnostic for cruciate rupture, but are helpful in confirming joint disease and also to rule out other musculoskeletal problems.

SURGERY IS THE TREATMENT OF CHOICE WITH THIS CONDITION! Varied surgical techniques are available for this disease. At our hospital we perform the Extra-Articular method—strong nylon is fixed in a figure 8 pattern on either side of the joint to stabilize the knee. The joint is also examined for meniscal damage which, if found, is removed. The meniscus is poorly vascularized and will not heal on its own if damaged. After stabilization and removal of damaged cartilage, the joint capsule is tightened to prevent abnormal movement. The leg is then usually supported with a heavy bandage for a period of 1 to 3 weeks while the knee joint is healing. Referral to a specialist for this surgery is available to all of our clients.

Physical therapy (e.g. ice packing, range of motion exercises and massage)post surgery is important for improving mobility and strength.

Even after surgery, recovery (rehabilitation) may take weeks to months depending upon the individual. A return to complete athletic function is uncommon. After surgery, some arthritis will occur due to the knee injury. However, the amount of arthritis will be less with surgery than without surgery. Twenty to forty percent of dogs with unilateral cranial cruciate rupture will have rupture involving the other knee within 1 ½ years.

Conservative Medical Therapy

Small dogs or those with partially torn ligaments may be treated conservatively with anti-inflammatory medications and rest. However, surgery is RECOMMENDED FOR ALL DOGS. It speeds recovery, minimized degenerative changes, and enhances function.