Muscular and tibiofemoral joint forces during isokinetic concentric knee extension

The purpose of this study was the examination of muscular and tibiofemoral forces during concentric isokinetic knee extension at angular velocities ranging from 30 to 210 deg s−1, using a two-dimensional biomechanical model. Five males without knee joint injury history participated in the study. The maximum moment ranged from 226.2 Nm at 30 deg s−1 to 166.4 Nm at 210 deg s−1. The maximum muscular force ranged from 7.5 times body weight at 30 deg s−1 to 5.7 at 210 deg s−1. The compressive tibiofemoral force ranged from 7.5 times body weight at 30 deg s−1 to 5.7 at 210 deg s−1 and the shear tibiofemoral force ranged from 0.9 to 0.8 times body weight respectively. These results indicate that the forces developed during maximal isokinetic knee extension are significantly reduced relative to other powerful dynamic activities but are higher than joint forces during simple walking and cycling activities. Appropriate precautions and adjustment of the isokinetic protocol are required in the final phases of joint injury rehabilitation.