Fig. 14

Force-deformation curves during AP tests. The force–deformation curves from the first trial of the constrained AP tests (CT, thin grey dotted line) and unconstrained AP tests using FPH (thin black dash-dotted line), FPA (thick grey dashed line) and FPHFM (thick line) at (a) 0° and (b) 30° flexion. In contrast to the posterior stiffness, the anterior stiffness started to differ after 5 mm of anterior deformation while larger anterior stiffness was found using the CT method both at 0° and 30° knee flexion during AP tests. During CT where significant constraining forces and moments were required, the target force was reached with smaller displacement, indicating less laxity, when compared to those of the unconstrained tests using the three unconstrained control methods, especially during the anterior drawer test