[Chronic posterior instabilities].

As an introduction, isolated posterior, posterolateral, posteromedial, as well as combined posterior stability are defined. Rupture of the posterior cruciate ligament leads to pathological patterns for both concentric and eccentric quadriceps movements. Special attention is drawn to the significance of the peripheral stabilizers and their influence on instability. Ruptures of the posterior cruciate ligament are commonly followed by a phase of functional adaptation, functional tolerance, and arthrotic decompensation. Diagnosis should not only be based on the posterior drawer test, but also consider stability tests in the frontal plane and eventual rotational instabilities. What constitutes adequate therapy is still a subject of controversy today. Among the operative procedures, the most common are the pes anserinus graft according to Hey-Groves and Lindemann, the gastrocnemius graft of Hughston and Insall, the free patellar ligament graft, and synthetic replacement. The decision about indications for surgery should not be made earlier than 18 months after the accident, when the phase of functional adaptation has been completed.