The effect of immobilization on goat knees following reconstruction of the anterior cruciate ligament.

Significant patellofemoral chondromalacia was observed three months after operations on goat knees that had an excised anterior cruciate ligament (ACL) replaced and then were immobilized for six weeks with a rigid external pin and frame fixator. To determine if the patellofemoral morbidity rate could be reduced, another group of goats was treated with the same operation but without immobilization. The legs of the animals in the immobilized group had muscle weakness and the animals only occasionally used their legs for the next three to four weeks. The animals in the mobilized group protected the leg for only one to two days after surgery, and by ten to 12 days were actively moving the knee. Severe patellofemoral articular cartilage erosions occurred in the immobilized goats but not in the mobilized group. Postoperative immobilization was detrimental to the joint function and to a successful ACL reconstruction.