The findings in my first 150 consecutive arthroscopies of the knee joint, performed with the Watanabe arthroscope, have been presented. Although the technique is somewhat demanding and considerable experience is required before the procedure can be done satisfactorily, it is without doubt a safe maneuver of great value to any orthopaedic surgeon who has enough interest to try to make an accurate diagnosis of a knee lesion, rather than just opening the joint "to have a look around." Any orthopaedist who sees many patients with knee injuries and disabilities will be fully rewarded for the time required to learn to do a good examination.

Sixty of the 150 knees in which arthroscopies were performed were subsequently operated on. In forty-eight of these knees, the arthroscopic findings were confirmed at operation. In the remaining knees, there were six false negative and six false positive findings. The false negatives were errors which could be explained by in-experience or poor visualization caused by cloudy or bloody fluid. The false positives were in knees in which strands of synovium floating in the saline-filled joint were misinterpreted as cartilage degeneration or loose bodies, again because of lack of experience.

Besides its obvious value, especially in difficult diagnostic problems, arthroscopy provides a means for morphologic follow-up of patients who have had prior surgery. The systematic use of arthroscopy should shed light on the ability of cartilage to repair itself, the seemingly protective effect of salicylates on damaged cartilage, and the like. The Watanabe arthroscope also provides a method of studying the interior of the knee joint without disturbing normal relationships, particularly the patellofemoral joint which can be visualized when the knee is in positions in which the patellofemoral joint cannot be visualized roentgenographically, notably between full extension and 60 degrees of flexion.