Indications for conservative treatment of knee ligament injuries can be established for all grade I or II sprains (partial tears), as well as isolated grade III sprains (complete tears) of the posterior cruciate ligament (PCL) and medial collateral ligament (MCL). These injuries should be treated with immediate mobilization. Only in isolated partial anterior cruciate ligament (ACL) tears without a positive pivot shift phenomenon is conservative treatment justified. However, many of these injuries may require operative reconstruction later. In complete ACL tears the surgical treatment consists of primary reconstruction or augmented primary repair. Today, the middle third of the patella tendon with the bone blocks is regarded as the "gold standard" for augmented repairs and late reconstructions. For the present, there is no place for synthetic prostheses in the treatment of an acute ACL rupture. Allograft replacement of the ACL must now be considered an experimental procedure. In the reconstruction of the PCL the above mentioned patella tendon graft is also preferable. Lateral collateral ligament (LCL) tears, especially if they are combined with ruptures of posterolateral ligament complex, should be repaired immediately after the injury. In these injuries late reconstructions are difficult and the results are poor. Conservative treatment of partial tears and postoperative treatment of reconstructed ligaments is twofold: on the one hand, the healing tissue should be protected and on the other hand, atrophy and wasting of uninjured tissue should be avoided. Overload and stretching of the injured ligaments should be eliminated with the aid of a suitable knee brace, but early range of motion exercises of the knee are allowed immediately.(ABSTRACT TRUNCATED AT 250 WORDS)