Tibiofemoral joint forces during maximal isokinetic eccentric and concentric efforts of the knee flexors

OBJECTIVE: The examination of muscular and tibiofemoral joint forces during maximal efforts of the knee flexors. DESIGN: The muscular and tibiofemoral joint knee forces during eccentric and concentric isokinetic efforts of the knee flexors were determined using a two-dimensional mathematical model. BACKGROUND: The examination of joint and muscle loading during isokinetic movements is important for the determination of safety of this exercise. METHODS: Ten healthy males performed three maximal isokinetic concentric and eccentric efforts of the knee flexors at angular velocities of 30 degrees s(-1), 90 degrees s(-1), 120 degrees s(-1) and 150 degrees s(-1). The muscular, tibiofemoral shear and compressive joint forces were determined using a two-dimensional model. RESULTS: The maximum muscular force ranged from 3.44 (Standard deviation, 1.32) times body weight to 6.19 (1.78) times body weight. The tibiofemoral compressive force ranged from 2.62 (1.17) times body weight to 5.89 (1.99) times body weight occurring at angles ranging from 0 degrees to 40 degrees of knee flexion. The posterior shear force ranged from 2.61 (1.33) times body weight to 3.89 (1.62) times body weight and was observed at angles ranging from 50 degrees to 80 degrees of knee flexion. Two-way analysis of variance designs indicated significant effects of type of muscle action and angular velocity on muscle and compressive forces (P<0.05). In contrast, the shear force was not affected by the type of muscle action or the angular velocity (P>0.05). CONCLUSIONS: Isokinetic efforts of the knee flexors induce high tibiofemoral joint forces, especially during high-speed eccentric tests.