Knee Rotation and Loading during Spin and Step Turn

Abstract

The tibia axial rotation and knee joint valgus torque may increase anterior cruciate ligament (ACL) tension in direction changes during daily activities. The purpose of the study was to compare knee joint rotation and torque between step turn and spin turn in direction change following walking downstairs. The knee joint axial rotation and valgus torque were quantified from 20 healthy subjects. Significant differences were found between 2 turn strategies and between 2 legs. Spin turn showed significantly greater internal tibia rotation (13.5°±5.9°), greater tibia rotation range of motion (-15.1°∼13.5°) than step turn (5.1°±5.2° and -11.5°∼5.1°) for both legs. Significantly greater peak valgus torque during spin turn (-0.91±0.33 Nm/kg) was found than that during step turn (-0.25±0.32 Nm/kg) for the left leg, while there was no significant difference between 2 turn strategies for the right leg (spin turn: -0.44±0.23 Nm/kg, and step turn: -0.40±0.27 N/kg). Excessive internal axial rotation combined with higher valgus torque may make the ACL and ACL graft more vulnerable to injury. The study indicated that, for right dominant people, turning with right leg or using step turn might reduce the stress on the ACL or ACL graft after ACL reconstruction.