Different views about the biomechanics of the knee joint and late re construction of ligamentous injuries underline the obstacles impeding the establishment of generally acceptable principles for the treat ment of such lesions. As late as June 1976, HUGHSTON emphasized in the Journal of Bone and Joint Surgery that in spite of excellent anatomic studies, substantial uncertainty still prevails in knee joint surgery. Even the signifi cance of the anterior drawer sign for ruptures of the anterior cru ciate ligament is interpreted quite diversely, as illustrated in a comparison of HUGHSTON, GIRGIS, TORG, and SCHIECK, who give varying opinions concerning the indication related to the age of the patient or possible earlier joint damage as well as concerning the prognosis for untreated knee joints. The question still remains as to how often an intra-articular ligamentous replacement should be carried out in addition to extra-articular techniques (0 'DONOGHUE, SLOCUM, NICHOLAS, HUGHSTON). Lastly the question of synthetic ligament replacement must be clarified. After basic research has well advanced, clinical ex perience must be discussed. Statements concerning the therapeutic value of diverse procedures based solely on knowledge of the literature remain problematic. For this reason a workshop was held at the University of Heidelberg in the Orthopedic Clinic (Head: Prof. Dr. H. COTTA) in June 1977, with the aim of bringing together representatives of the different leading schools in a round table discussion to comment on still unsolved ques tions.