To perform surgery in the inaccessible area of the posterior compartment of the knee joint with the conventional anterior-posterior triangulation technique, we have used a direct posteromedial-posterolateral triangulation technique. This technique has been easy and safe in performing arthroscopic surgery in the posterior compartment, including synovectomy of 350 knees and removal of loose bodies in 12 knees. Using this method in addition to conventional anterior-posterior triangulation, the whole area of the posterior compartment could be covered for performing arthroscopic surgery.