[Which knee ligaments must be reconstructed in anterior and posterior valgus and varus instability? An experimental study].

This study aims to localize the ligamentous lesions in distinct knee joint instabilities. For that reason 41 human cadaver knee joint specimens were tested in a three-dimensional determined apparatus. Ligaments were successively dissected and forces and torques were introduced. Both cruciates are the dominant structures in preventing straight anterior und posterior movement of the tibia. As a supporting element the postero-medial capsule prevents anterior dislocation in ACL-deficient knees. Therefore extraarticular procedures in cruciate instabilities will not be successful. In contrast varus- and valgus instabilities resulted after transsection of a couple of ligaments. Valgus stability decreased after cutting the medial collateral, posterior oblique and both cruciate ligaments. The most important element in preventing straight varus instability was the lateral collateral followed by the posterior cruciate ligament, while the popliteus tendon had only little influence. Therefore in medial and lateral instabilities all supporting structures should be exposed and reconstructed.