Cranial Cruciate Ligament Injury

Rupture of the cranial cruciate ligament is one of the most common orthopedic injuries in veterinary medicine. Cranial cruciate ligament (CCL) rupture is the tearing of an important ligament is the stifle joint (knee). This injury results in partial or complete joint instability, pain, and lameness. If the injury is not treated, lameness often persists and degenerative joint disease (arthritis) often results. In some cases, a pad of cartilage within the knee, called a meniscus, tears along with the CCL.  

Overview

The knee joint of all animals works like a hinge, keeping the leg stable as it bends. A normal dog or cat knee joint is made up of two bones (the femur and tibia) the cranial and caudal cruciate ligaments, the meniscus, the patella (knee cap), the patellar ligament, and the collateral ligaments. The cruciate ligaments are contained inside the joint and are responsible for limiting forward and backward movement of the femur in respect to the tibia. The meniscus is a cartilage pad within the knee that serves as a shock absorber during movement. The patella acts to ease movement the thigh muscles as they pass over the knee. The medial and lateral collateral ligaments limit side-to-side movement of the knee.

Incidence

Cranial Cruciate Ligament rupture occurs more frequently in dogs than in cats. It is one of the most common orthopedic injuries in dogs. CCL rupture occurs in all sizes of dogs, but is more common in large and giant breed dogs. Obese animals are at greater risk of ligament rupture than normal weight animals. The disease can be seen in any age of dog, but is more common in middle-aged dogs. Ligament rupture can occur suddenly, but sometimes tearing is partial and occurs gradually, resulting in low-level lameness that may improve initially over time. In those cases complete rupture eventually does occur.  

Causes and Clinical Signs

CCL rupture can be acute or chronic. Acute rupture of the CCL is caused by sudden, severe twisting of the ligament, such as when the animal steps in a hole while running or turns with its paw remaining planted. In chronic cases, the ligament degenerates prematurely and eventually tears.

Hind limb lameness 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 a little after several weeks. However, lameness is likely to return. Swelling within the knee joint is seen with acute cases. Pets with chronic ligament rupture will exhibit thickening of the tissues around the joint.

Diagnosis

Diagnosis of CCL rupture is most often made on physical examination. The knee is palpated for evidence of pain or instability. Pain from a ruptured CCL can be severe, resulting in muscle tension that restricts joint movement. Therefore, sedation may be required to move the limb to the extent needed to make the diagnosis. 

Radiography (x-rays) may suggest, but cannot confirm, a partial tear or a complete rupture. Unfortunately, ligament injuries do not show up on radiographs; however, there may be 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. However, the canine stifle joint is too small to allow stabilization procedures to be performed through arthroscopy.

Treatment 

The goal of CCL rupture treatment is to alleviate pain and increase use and mobility. Conservative therapy and surgery 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. Conservative management is typically not very effective in dogs that weight more than 30 pounds. This treatment is somewhat helpful in cats, except for those who are large framed or overweight.

Surgery is the preferred treatment in dogs over 30 pounds and larger cats. Surgical treatment will restore function to the affected limb in most cases. Surgery will also slow, but not stop, degenerative joint disease.

Many techniques have been described for the repair of CCL rupture in animals. Currently two techniques are used most commonly: Lateral Imbrication and Tibial Plateau Leveling Osteotomy (TPLO). The type of technique chosen depends upon the size, type, and age of the pet 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. When the Lateral Imbrication technique is used, a either a titanium implant with integrated Fiberwire® suture or one or more large gauge nylon sutures secured with surgical steel clamps are placed between the femur and tibia to closely approximate the angle of the natural ligament and restore joint stability. If a TPLO is performed, the angle of the tibia relative to the femur is changed to prevent the tibia from sliding forward.

No matter which type of surgery is performed to correct the ligament rupture, the patient should rest until the joint is fully healed to avoid re-injury. During the post-operative period the pet will require daily physical therapy for the first seven to 10 days followed by a gradual return to normal activity. Weight loss is recommended for overweight patients as up to 40% of dogs will develop a similar rupture in the other hind leg, especially if they remain over weight.

 

If you have any questions regarding cruciate injuries and their treatment please do not hesitate to ask your veterinarian.