Transection of the anterior cruciate ligament 2 weeks after ipsilateral hindlimb deafferentation leads to osteoarthritis of the knee joint within 3 weeks. We analyzed the gait of six dogs that underwent this procedure in order to identify kinematic changes that could account for this rapid joint degeneration. All animals were video taped, 1, 3, 6, 9 and 13 weeks after surgery while they trotted on a treadmill.
In each dog, extension of the hip, knee and ankle joints of the unstable limb was increased, and the yield phase of the unstable knee was delayed or attenuated. When killed, five of six dogs showed a large full-thickness cartilage ulcer on the distal and/or anterior surface of the medial femoral condyle of the unstable knee; in the sixth dog, a smaller ulcer was observed. However, the severity of pathology in each individual was not obviously related to difference among the dogs in postoperative joint kinematics.
These data, and results of prior studies in humans and dogs, suggest that knee hyperextension resulting from limb deafferentation, and knee instability resulting from anterior cruciate ligament transection, operate in concert to create a mechanical environment (i.e., increased tibiofemoral separation and changes in the loading of articular surfaces) that results in rapid joint breakdown.