BIOMECHANICS OF THE KNEE DURING CLOSED KINETIC CHAIN AND OPEN KINETIC CHAIN EXERCISES

Abstract

269 Although closed (CKCE) and open (OKCE) kinetic chain exercises are used in athletic training and clinical environments, there are currently no data comparing knee joint biomechanics while performing these exercises dynamically. The purpose of this study was to quantify knee forces and muscle activity during CKCE (squat and leg press) and OKCE (knee extension). Ten male subjects performed three repetitions of each exercise at their 12-repetition maximum. Kinematic, kinetic and electromyographic data were calculated using video cameras (60 Hz), force transducers (960 Hz) and EMG (960 Hz). Mathematical muscle modelling and optimization techniques were employed to estimate muscle and ligamentous forces. Quadriceps activity was significantly greater in OKCE near full knee extension and greater in CKCE near full flexion. Hamstring activity remained low throughout the leg press and OKCE. During the knee-extending phase the squat generated significantly greater hamstring activity than the leg press and OKCE. Tibiofemoral compressive force was greatest in OKCE near full knee extension and greatest in CKCE near full knee flexion. For all exercises, approximately 3000 N of maximum tibiofemoral force was produced. Maximum tibiofemoral force was produced between 53-93° knee angle during CKCE and between 39-57 ° during OKCE. For all exercises, PCL tensile forces generally increased with knee flexion and decreased with knee extension. During CKCE, the PCL was always in tension. During OKCE, the PCL was in tension at greater than 25 ° knee angle, while the ACL was in tension near full knee extension (15-25 °). Peak PCL forces were near 2000 N for CKCE and near 1000 N for OKCE. Patellofemoral forces generally increased with knee flexion and decreased with knee extension. OKCE produced significantly greater patellofemoral forces than CKCE at knee angles less than 57 °, while CKCE generated significantly larger patellofemoral forces than OKCE at knee angles greater than 85 °. Maximum patellofemoral force exceeded 4000 N for all three exercises. An understanding of these results can help in balancing muscle strengthening with ligament and bone loading.