Comparison of tibiofemoral joint forces during open-kinetic-chain and closed-kinetic-chain exercises

The purpose of this study was to analyze forces at the tibiofemoral joint during open and closed-kinetic-chain exercises. Five healthy subjects performed maximum isometric contractions at 30, 60, and 90 degrees of knee flexion during open-kinetic-chain extension, open-kinetic-chain flexion, and closed-kinetic-chain exercises. Electromyographic activity of the quadriceps and hamstrings, as well as load and torque-cell data, were recorded. Tibiofemoral shear and compression forces were calculated with use of a two- dimensional biomechanical model. The results showed that, during the open- kinetic-chain extension exercise, maximum posterior shear forces (the resisting forces to anterior drawer) of 285 ± 120 newtons (mean and standard deviation) occurred at 30 degrees of knee flexion and maximum anterior shear forces (the resisting forces to posterior drawer) of 1780 ± 699 newtons occurred at 90 degrees of knee flexion. The closed-kinetic-chain exercise produced significantly less posterior shear force at all angles when compared with the open-kinetic-chain extension exercise. In addition, the closed- kinetic-chain exercise produced significantly less anterior shear force at all angles except 30 degrees when compared with the open-kinetic-chain flexion exercise (p < 0.05). Analysis of tibiofemoral compression forces and electromyographic recruitment patterns revealed that the closed-kinetic- chain exercise produced significantly greater compression forces and increased muscular co-contraction at the same angles at which the open- kinetic-chain exercises produced maximum shear forces and minimum muscular co-contraction. The reduction in tibiofemoral shear force that was observed during the closed-kinetic-chain exercise was a result of the more axial orientation of the applied force and the phenomenon of muscular co- contraction. CLINICAL RELEVANCE: This study demonstrated significant differences in tibiofemoral joint forces between the open and the closed- kinetic-chain exercises. The results suggest that closed rather than open- kinetic-chain exercises should be emphasized as a means of strengthening the muscles of the knee in athletes after injury to or reconstruction of the anterior cruciate ligament.