COMPARISON OF TIBIOFEMORAL JOINT FORCES DURING OPEN-KINETIC-CHAIN ANDCLOSED-KINETIC-CHAIN EXERCISES

The purpose of this study was to analyze forces at the tibiofemoral jo int during open and closed-kinetic-chain exercises. Five healthy subje cts performed maximum isometric contractions at 30, 60, and 90 degrees of knee flexion during open-kinetic-chain extension, open-kinetic-cha in flexion, and closed-kinetic-chain exercises. Electromyographic acti vity of the quadriceps and hamstrings, as well as load and torque-cell data, were recorded. Tibiofemoral shear and compression forces were c alculated with use of a two-dimensional biomechanical model. The resul ts showed that, during the open-kinetic-chain extension exercise, maxi mum posterior shear forces (the resisting forces to anterior drawer) o f 285 +/- 120 newtons (mean and standard deviation) occurred at 30 deg rees of knee flexion and maximum anterior shear forces (the resisting forces to posterior drawer) of 1780 +/- 699 newtons occurred at 90 deg rees of knee flexion. The closed-kinetic-chain exercise produced signi ficantly less posterior shear force at all angles when compared with t he open-kinetic-chain extension exercise. In addition, the closed-kine tic-chain exercise produced significantly less anterior shear force at all angles except 30 degrees when compared with the open-kinetic-chai n flexion exercise (p < 0.05). Analysis of tibiofemoral compression fo rces and electromyographic recruitment patterns revealed that the clos ed-kinetic-chain exercise produced significantly greater compression f orces and increased muscular co-contraction at the same angles at whic h the open-kinetic-chain exercises produced maximum shear forces and m inimum muscular co-contraction. The reduction in tibiofemoral shear fo rce that was observed during the closed-kinetic-chain exercise was a r esult of the more axial orientation of the applied force and the pheno menon of muscular co-contraction. CLINICAL RELEVANCE: This study demon strated significant differences in tibiofemoral joint forces between t he open and the closed-kinetic-chain exercises. The results suggest th at closed rather than open-kinetic-chain exercises should be emphasize d as a means of strengthening the muscles of the knee in athletes afte r injury to or reconstruction of the anterior cruciate ligament.