Posterior cruciate ligament (PCL) injuries are more common than has been previously reported. Recent clinical and basic science studies have helped define the important functional anatomy and biomechanics of this "forgotten" ligament and have raised questions regarding the reported benign natural history of isolated tears of the PCL. While recent technical advancements in the application of magnetic resonance imaging to knee ligament injuries may assist in identifying PCL tears, the posterior drawer test remains the "gold standard" for diagnosis. Numerous treatment options have been proposed, but anatomical reconstructions have yielded consistently good clinical results. A review of our current knowledge of the basic science and clinical studies on the posterior cruciate ligament is presented to stimulate further interest and research in this exciting area.