External loading of the knee joint during running and cutting maneuvers

Purpose: To investigate the external loads applied to the knee joint during dynamic cutting tasks and assess the potential for ligament loading. Metho ds: A 50-Hz VICON motion analysis system was used to determine the lower li mb kinematics of 11 healthy male subjects during running, sidestepping, and crossover cut. A kinematic model was used in conjunction with force place data to calculate the three-dimensional loads at the knee joint during stan ce phase. Results: External flexion/extension loads at the knee joint were similar across tasks; however, the varus/valgus and internal/ external rota tion moments applied to the knee during sidestepping and crossover cutting were considerably larger than those measured during normal running (P < 0.0 5). Sidestepping tasks elicited combined loads of flexion, valgus, and inte rnal rotation, whereas crossover cutting tasks elicited combined loads of f lexion, varus, and external rotation. Conclusion: Compared with running, th e potential for increased ligament loading during sidestepping and crossove r cutting maneuvers is a result of the large increase in varus/valgus and i nternal/external rotation moments rather than any change in the external fl exion moment. The combined external moments applied to the knee joint durin g stance phase of the cutting tasks are believed to place the ACL and colla teral ligaments at risk of injury, particularly at knee flexion angles betw een 0 degrees and 40 degrees, if appropriate muscle activation strategies a re not used to counter these moments.