[Posterior knee instability].

Due to improved diagnostic methods, posterior knee instabilities are detected more often. Up to now, however, the natural history of isolated ruptures of the posterior cruciate ligament is not known exactly. After conservative treatment, the first degenerative changes occur after about 10-15 years, mainly in the femoropatellar joint and the medial compartment. In complex posterior instabilities with lesions of the secondary stabilizers, the posterolateral structures, the lateral collateral ligament, and the leg alignment play an important role. Conservative or operative treatment of posterior knee instabilities depends on the extent of the lesion, the violated structures, and the impairment of the patient. For replacement of the posterior cruciate ligament, grafts from the patella ligament, the quadriceps tendon, and the hamstrings are used most frequently. In simultaneous lesions of the posterolateral corner of the knee joint, additional ligament-stabilizing methods are necessary.