Assessment of anteroposterior instability of the knee during gait.

A noninvasive kinematic recording technique involving geometric modeling of the knee joint was employed to determine anteroposterior displacements of the knee during walking. The model estimated how much the femoral condyles slid and rolled on the tibial plateau. Movement not due to sliding or rolling was attributed to horizontal translation of the tibia with respect to the femur. Thirty normal adults participated in this study. A three-dimensional analysis system with noninvasive skin markers was employed to collect kinematic data of the femur and tibia during walking. Within-session and between-session reliabilities were high in the tested subjects. Normal subjects had an average of 5.5 mm of maximum anterior displacement of the tibia during stance phase of walking. These results differed neither between left and right knees, nor between men and women. Dynamic instability of the knee during walking can be reasonably measured by the proposed method in normal subjects.