Biomechanic studies reinserting the medial collateral ligament to correct a chronic anteromedial instability of the knee joint.

One possibility to correct a chronic anteromedial instability of the knee joint is the osseous reinsertion and tightening of the medial collateral ligament. In experiments with a string model and strain gauges attached to the ligaments we investigated the advantages and/or disadvantages of the femoral and tibial reinsertion. Regarding the tension mechanism the medial collateral ligament reacts considerably more sensitivity to the femoral reinsection in proximal-dorsal direction than to the tibial-reinsertion in distal-ventral direction. An accurate knee flexion between 40 and 60 degrees has to be provided reinserting the ligament in proximal-dorsal direction to avoid excessive tension and resulting destruction of the ligament. However the reinsertion of the ligament in distal-ventral direction, independently from the flexion of the knee, always approximates the natural tension of the anterior and posterior margin of the untreated ligament. Biomechanically the reinsertion in distal-ventral direction to tighten the loose ligament seems to be preferable to the reinsertion in proximal-dorsal direction.