Three-dimensional kinematics of the intact and cranial cruciate ligament-deficient stifle of dogs.

Joint motion was measured for the intact and cranial cruciate ligament (CCL)-deficient stifle in five large dogs using an instrumental spatial linkage and radiophotogrammetry. The linkage was directly attached to the bones using modified bone plates. Motion data were presented in terms of a clinical coordinate system. Stifle kinematics were highly reproducible for a given dog. For intact stifle kinematics, the swing phase included flexion-extension, internal-external rotation and abduction-adduction, while stance-phase kinematics included only flexion-extension. Loss of the CCL altered joint kinematics over the entire gait cycle. At the swing-stance transition, the CCL-deficient stifle demonstrated an abrupt cranial subluxation of the tibia which was sustained throughout stance. At the beginning of the swing phase the CCL-deficient joint returned to the cranial-caudal alignment seen in the intact joint. The dog's stifle was shown to be CCL-dependent during stance. The dog compensated for CCL loss by reducing the external limb load and by carrying the limb in greater flexion throughout the gait cycle, but was unable to prevent joint subluxation during stance. Stifle kinematics are greatly altered following CCL loss. It is the repetitive, mechanical, dynamic subluxation in a CCL-deficient joint which may be the cause of joint degeneration.