Does Lift-Off Occur During Deep Squat?

Kneeling, deep squatting, crouching, and gardening represent activities that require flexing the knee maximally. Yet, the present-state-of-the-art of knee mechanics does not provide an accurate understanding of how this joint functions in deep flexion in normal individuals as indicated by Kurosaka, et al. [1]. This limited understanding of the complex 3-D dynamic tibio-femoral and patello-femoral motions past 130° of knee flexion hinders the development of a prosthesis that would provide for full flexion of the knee. One of the questions that is being presently debated is whether lift-off occurs during deep squat or not [2, 3]. The purpose of this paper is to provide an answer to this question by determining the kinematics of the knee while it is maximally flexed, past 155 degrees of flexion.