Smoothness of Knee Movement at the Stance Phase in Mild Osteoarthritis of the Knee

Abstract

Aims: The purposes of this study were to clarify the changes in smoothness of each phase by making use of the angular jerk cost for the smoothness of the knee joint motion at the stance phase in patients with osteoarthritis, to verify the relationship between the kinetics variables and the smoothness, and to clarify the dynamics in osteoarthritis by comparison with healthy subjects using the angular jerk cost of knee flexion or extension. Methods: The osteoarthritis group comprised 19 knees of 12 subjects with a Kellgren–Lawrence grade of 1 in at least one knee. The control group comprised 10 healthy adults. The subjects walked barefoot along a 10-m walkway at their self-selected habitual speeds. The stance phase of gait was defined as four periods To calculate the smoothness of the knee joint movement, the angular jerk cost of the knee joint angle during the stance phase was calculated by differentiation three times using the knee joint angle data. Results: The angular jerk cost was increased in the early stance phase in both groups. Only the osteoarthritis group showed a large angular jerk cost in the late stance phase. The ground reaction force in the osteoarthritis group showed a small value in the stance phase compared with the control group. Conclusion: The movement of the knee joint at the initial stance phase had a strategy to ensure the smoothness of the movement by decreasing the change in the angular acceleration in accordance with the impairment disorder. In addition, the smoothness of the knee joint movement was decreased at the late stance phase compared from the loading response to mid-stance period in the osteoarthritis group, and the propulsion for forward movement of the body was exerted by a change involving a large angular acceleration with a large force.