Update on the aetiopathogenesis of canine cranial cruciate ligament disease.

Cranial cruciate ligament disease (CCLD) is the most common cause of hindlimb lameness in the dog, being associated with and eventually leading to stifle osteoarthritis. Canine cranial cruciate ligament disease is a gradual degeneration of the ligament extracellular matrix (ECM) leading to ligament rupture. The aetiopathogenesis of this condition is still poorly understood but several risk factors have been identified such as breed, bodyweight, gender and conformation. Recent developments in this area include the role of genetics, stifle joint conformation, ligament ECM metabolism, and inflammation associated with immune-mediated disease within the stifle joint. A genetic mode of inheritance has been demonstrated in the Newfoundland which is predisposed to CCLD. Increased cellular metabolism within the cranial cruciate ligament has been directly associated with increased craniocaudal stifle joint laxity in dog breeds at high risk of CCLD. Conformation abnormalities, such as a narrowed distal femoral intercondylar notch, in high risk breeds have been shown to be associated with alterations in cranial cruciate ligament ultrastructure. Increased production of inflammatory cytokines, such as cathepsins and interleukins, by the stifle synovial cells may occur secondary to or may be an inciting cause of ligament degeneration. Future research endeavours will focus on the association between immune-mediated response and fibrocartilaginous metaplasia and matrix degradation within the cranial cruciate ligament, and whether this can be altered in all susceptible dogs or only certain breeds.