Numerous manipulative tests have been described for the meniscus tear and the McMurray test is probably most commonly used. The medial meniscus is checked by externally rotating the leg as far as possible, and slowly extending the knee while listening and feeling for a click by palpating the posteromedial margin of the joint. The lateral meniscus is checked by internally rotating the leg and feeling for a click by palpating the posterolateral margin of the joint. But, there are paradoxical cases in which internal rotation elicits a click in the medial compartment of the knee during the McMurray test. One hndred thirty-one consecutive patients with positive McMurray test were evaluated by arthroscopy. Among them, 27 patients revealed pain or clicking either in the medial compartment of the knee in the internally rotated position or in the lateral compartment of the knee in the externally rotated position, contrary to the conventional McMurray test. The authors analysed these paradoxical findings arthroscopically with regard to the relationship between the type of meniscus tear and the direction of rotation that elicited catching and displacement of the torn portion of the meniscus during the McMurray test. The authors confirmed displacement of the meniscal tear by rotation in the opposite direction to the conventional McMurray test in the following situations.: 1) anteriorly based posterior oblique tear with anterior displacement 2) bucket handle tear in the posterior half 3) posterior tear of the medial meniscus with severe anterolateral instability. Pain or click elicited by rotation in the opposite direction to the conventional McMurray test suggested the above-mentioned types of meniscal tear on the side of the compartment where the click was elicited.