Animation 3: Knee model with ligament fibre arrays

Animation 3 is an elaboration of the four-bar linkage model with each of the cruciate ligaments (ACL & PCL) represented as arrays of fibres. The PCL is shown as two bundles of fibre. In extension, all fibres of the ACL and the posterior fibres of the PCL are assumed to be tight and are shown straight. In extension, the anterior fibres of the PCL are assumed to be slack and are shown buckled. Fibres slacken or tighten depending on their position relative to the flexion axis of the joint.