The increase of knee lesions within the last years has provoked a generally more intensive discussion about the functional anatomy, the biomechanics and the pathophysiology of the capsule and ligaments of the knee joint. Several authors have stressed the importance of the active and passive factors, stabilizing the knee joint. The injury to a single element leads to different instabilities, as proven by meticulous clinical and radiological diagnostic procedures. The progress in the treatment of fresh and old injuries of knee ligaments is connected with the names of O'Domoghue, Slocum, Larson, Hughston, Nicholas and Trillat. For a fresh completely ruptured ligament surgery is recommended. Torn menisci are reattached whenever possible. An initial graft can be necessary for ruptures of the anterior cruciate ligament. Complex injuries, which are found most frequently, have to be dealt with completely. Old injuries of capsule and ligaments may require a plastic reconstruction. For the reconstruction of the anterior cruciate ligament it has been proven useful to take distally attached tendons of the pes anserinus group as well as the free graft from the central 1/3 of the patellar ligament. Rotational instabilities have to be dealt with according to the type of instability. The techniques of Slocum and Larson and the "five in one" reconstruction by Nicholas have to be emphasized as treatment of the anteromedial rotational instabilities. McIntosh has shown a procedure which seems to be successful for anterolateral rotational instabilities. Several techniques have been compared with our own experiences and late results studied. The point is stressed that further progress has to be made for the treatment of injuries to ligaments of the knee.