Abstract

Rupture of cranial cruciate ligament (CCL) is a common problem in dogs. This condition can cause deterioration in limb function and progression of osteoarthritis (OA). Pathology associated with CCL rupture is often called CCL disease. Its significance in veterinary medicine has been well documented in the literature. Despite being the most common cause of lameness in dogs, diagnosis of this condition can be challenging, particularly in its early phase. Treatment of this condition typically requires surgery.

Background and Significance

Cranial cruciate ligament rupture is one of the most common causes of lameness in adult dogs. The CCL plays a crucial role in limb function by maintaining stability of the stifle joint throughout the range of motion, thus injury to the CCL will result in joint instability and predispose the joint to degenerative changes. CCL rupture is particularly common in large and giant breed dogs; however, any breed, size, or age of dog may be affected. Osteoarthritis, meniscal injury, and persistent lameness commonly occur with CCL rupture. Treatment of this condition typically requires expensive surgery and lengthy physical rehabilitation in order to improve limb function and quality of life.

Epidemiology

Clinical features and treatment options have been well discussed in the veterinary literature; however, the exact disease mechanisms of canine CCL rupture remain undefined and controversial. Although trauma can cause acute CCL rupture, the majority of CCL ruptures occur under normal activity, and a number of previous studies suggest that the majority of CCL lesions are the result of chronic degenerative changes within the ligament.

Pathogenesis

There is conflicting evidence as to whether these degenerative changes are the primary cause of the ruptures, a secondary change caused by the ruptures, or the result of multiple factors. Studies have proposed several risk factors for CCL rupture, the most significant being breed, body weight, and neutering. Other factors have also been associated with CCL disease/rupture, such as aging, conformational variation, medial patella luxation, inactivity, and obesity. Currently, the exact etiology and pathogenesis of canine CCL rupture are undefined and controversial.

Pathophysiology

Pathology of CCL disease appears to involve a gradual degeneration of CCL itself, inflammatory disease in the stifle joint, partial rupture, progressive rupturing, complete rupture, and secondary disease such as progressive osteoarthritis and meniscal injury. Dogs with early CCL disease (i.e., minor partial CCL rupture) may have little or no palpable instability, but they are often presented with lameness and effusion of the stifle join. Major partial or complete CCL ruptures produce marked instability of the stifle joint, resulting in lameness and progressive degenerative change such as periarticular osteophyte formation, capsular thickening, and meniscal degeneration. As these changes progress, the joints become less unstable. Advanced or end-stage CCL disease may have little palpable stifle instability because of the periarticular fibrosis.

Diagnosis

Diagnosis of this condition can be challenging, particularly in its early phase. Manual examinations to elicit cranial translation of tibia relative to femur ("drawer" and "tibial thrust" tests) have been traditionally used to detect CCL rupture. However, only 50 to 70% of dogs with CCL rupture may show positive drawer or tibial thrust signs. Therefore, diagnosis of early CCL rupture should not rely solely on these tests and may require comprehensive approach based on multiple layers of evidence. Observation, palpation, manipulation, radiographs, and arthroscopy are commonly used to diagnose CCL disease. Joint fluid analysis and advanced imaging modalities (such as MRI, CT, and ultrasound) have been used to rule out other potential stifle diseases.

Management of CCL Rupture

Early CCL disease with minor partial rupture usually progresses to complete rupture over time. Early surgical intervention is generally recommended to improve limb function and to slow down progression of arthritic changes. Conservative management with rest and medication may result in temporary improvement of clinical signs; however, it almost always ends up in eventual decline of limb function. Therefore, conservative management of early CCL rupture is recommended only for geriatric or systemically ill patient that cannot undergo general anaesthesia and surgery.