Knee kinematics and kinetics during locomotor activities of daily living in subjects with knee arthroplasty and in healthy control subjects.

BACKGROUND AND PURPOSE Knee kinematics and kinetics have not been quantitatively studied during gait, stair negotiation, and rising from a chair in the same subjects, either among healthy control subjects or among subjects with knee joint impairments. Despite this paucity of data, rehabilitation goals often include achieving a specific peak knee torque at a specific, fixed angular velocity. SUBJECTS We compared the kinematic and kinetic performance of the knees in 15 subjects (19 knees) who had undergone knee arthroplasty (KA group) and 11 healthy subjects (22 knees) who served as a control group. The KA group subjects ranged in age from 61 to 78 years, and the control group subjects ranged in age from 26 to 88 years. The KA group subjects had had knee osteoarthritis, were > or = 1 year postsurgery, and were considered fully rehabilitated. METHODS All subjects were analyzed during barefoot paced walking, stair ascent and descent, and arising from a chair. RESULTS Compared with the control subjects, the KA group subjects had significantly different knee sagittal range of motion, angular velocities, and maximum knee moments during loaded knee extension. Vertical ground reactions did not differ significantly between groups. Both groups' maximum extension angular velocity exceeded 350 degrees/s during the swing phase of gait, but the maximum loaded extension velocity averaged only 140 degrees/s (during rising from a chair). Maximum knee flexion moments were approximately 10 to 15 N.m/%BW (knee moments normalized to percentage of body weight in newtons). CONCLUSION AND DISCUSSION We concluded that locomotor ADLs demand relatively slow loaded angular velocities and low knee torques, a factor that should be considered in knee postarthroplasty exercise prescription.