Evidence of mechanical load redistribution at the knee joint in the elderly when ascending stairs and ramps.

This study examined the external joint moments at the lower extremity in all three directions in a group of older and younger adults when ascending stairs and ramps. Twenty-eight older and 16 younger adults ascended a purpose-built staircase and ramp. A motion capture system and a force plate were used to determine the subjects' 3D kinematics and ground reaction forces. Calculation of the leg kinematics and kinetics was done by means of a rigid, three-segment, 3D leg model. Older had lower dorsiflexion and knee flexion moments but higher hip flexion moments than the younger adults, independent of locomotion condition. Concerning the other two planes, older adults showed higher adduction moments at the knee and hip joint, and higher knee internal rotation moments. Furthermore, the elderly showed a more external position of the shank in relation to the thigh at the initiation of the stance phase for the two conditions examined. The higher adduction and internal rotation moments at the knee when combined with the kinematic changes in the transverse plane for the elderly give evidence that older adults redistribute the mechanical load within the load bearing regions of the knee. We concluded that the redistribution in knee joint loading may increase the risk factors for developing knee osteoarthritis in the elderly.