Isolated posterior cruciate ligament (PCL) injuries are uncommon and can be easily missed with physical examination. The purpose of this article is to give an overview of the clinical, diagnostic and arthroscopic evaluation of a PCL injured knee. There are some specific injury mechanisms that can cause a PCL including the dashboard direct anterior blow and hyperflexion mechanisms. During the diagnostic process it is important to distinguish between an isolated or multiligament injury and whether the problem is acute or chronic. Physical examination can be difficult in an acutely injured knee because of pain and swelling, but there are specific functional tests that can indicate a PCL tear. Standard x-ray's and stress views are very useful imaging modalities but magnetic resonance imaging remains the gold standard imaging study for detecting ligament injuries. Every knee scope should be preceded by an examination under anesthesia. Specific arthroscopic findings are indicative of a PCL tear such as the "floppy ACL sign" and the posteromedial drive through sign. History, physical examination and imaging should all be combined to make an accurate diagnosis and initiate appropriate treatment.