Between 1974 and 1978 at the "Berufsgenossenschaftliche Unfallklinik" Frankfurt/Main 124 patients with lesions to the knee ligaments were treated; 117 patients could be followed up. All cases were classified according to the accident, the impact and the mechanism of the injury. The case-reports were supplemented by a graduation of the rotation stability and a general description of the own surgical technic and the postoperative care. For evaluation the surgically treated cases were divided according to the time they received treatment (immediately, early or late). All three groups were evaluated separately using the same objective and subjective criteria. It was found that the functional late results depended on the time of the first treatment. The findings led to the conclusion that injuries to the ligaments of the knee joint should be treated immediately by surgery.