Knee injuries are a major problem in competitive contact sports. During the past two years, the Radiology Department and the Sports Medicine Section of Orthopedic Surgery have been evaluating knee stability before and after knee surgery. For this purpose, tape recording of television fluoroscopy has been used. As an outgrowth of the evaluation of injured knees, knee-stabilizing systems have also been investigated. Adhesive tape support of a conventional type and the knee “cages” and supports commonly used have been considered by some to add little stability and also to limit the mobility of the player. Athletes who had had previous injuries and who have “loose” knees at the present time were used as subjects. The normal and injured knees were examined in the usual manner but with television observation and recording. The medial and lateral collateral ligaments were tested in extension and in 15° of flexion. The examination is very easily conducted as shown in Figure 1. The cruciate ligaments are evaluated...