Journal of Orthopedics. Translational Research and Clinical Application vol:3 issue:1 pages:27-37
Normal quadriceps function in the extended knee may help protect the joint from pathology related to daily activities. To better understand normal knee function, this study measured how quadriceps load affects knee kinematics and soft tissues lengths close to extension. Six cadaver knees were tested in a knee kinematics simulator which held the specimens quasi-statically in three positions, targeting 0° to 20° knee flexion. During each trial, quadriceps load increased from zero up to 220 N, while an optical motion capture system tracked the joint’s positions. A standard kinematic model was used together with CT scan data to measure eleven knee parameters, including knee joint rotations, anteroposterior translations, and soft tissue lengths. The average linear sensitivities of each parameter to quadriceps load were calculated and compared using ANOVA. Average tibial rotation and abduction at low flexion showed little response to increasing quadriceps load, whereas flexion angle was more sensitive, changing by 35-40° more per kN change in quadriceps load (p = 0.003). The anteroposterior position of the lateral femoral condyle had more variable sensitivity between specimens than the medial femoral condyle (p < 0.001). Patellar soft tissues generally were more variable in sensitivity than the femorotibial soft tissues. The sensitivity values presented here have not been previously reported and can be used to predict normal knee function in response to quadriceps load near extension.