Serial kinematic analysis of the trunk and limb joints after anterior cruciate ligament transection: Temporal, spatial, and angular changes in a canine model of osteoarthritis.

To help elucidate how sensation-mediated kinematics modulate the rate of development of osteoarthritis in the unstable knee, we have examined the serial kinematic changes in hind- and forelimb joints, and alterations in vertical movement of the rump, in six dogs followed for 26 weeks after unilateral anterior curciate ligament transection. Although marked changes in the temporal parameters occurred in treadmill gait acutely in all four limbs, by the sixth postoperative week the stance and swing durations had returned to within ±10% of the baseline values, where they remained until sacrifice. As the cruciate-deficient limb contacted the treadmill surface, the amount of flexion (yield) of the unstable knee and ipsilateral ankle was reduced 10-20° (P < 0.05). In contrast, flexion of the contralateral ankle and knee increased about 10° during yield (P < 0.05), which was associated with a 100% increase in the extent of vertical movement of the rump (P < 0.05). Hip extension in the unstable limb increased about 10° during stance (P < 0.05), which moved the support provided by this limb away from the dog's centre of gravity. Kinematic changes in the forelimb joints were only transient, and less extensive than those in the hind limb. Before ligament transection, the joint angles of comparable joints of the different dogs were remarkably similar at touchdown. After ligament transection, the variability of the ipsilateral hip and knee joints was initially markedly increased. However, by 26 weeks after surgery the ipsilateral hip and knee touchdown joint angles of all the cruciate-deficient dogs were again similar to one another. Thus, after a period of 'trial and error', the dogs responded similarly to unilateral cruciate deficiency. This response was probably modulated by sensory nerves and reduced the trauma to the unstable knee during locomotion. Presumably, this facilitated effective, but suboptimal locomotion, while slowing the rate of progression of osteoarthritis in the unstable joint compared to dogs with a deafferented hind limb and unstable joint.