Internal derangement of the knee: diagnosis by arthrography, arthroscopy, and arthrotomy.

Three hundred eighty-four cases involving all patients with meniscal or anterior cruciate ligament tears were examined surgically by 16 orthopedic surgeons over two distinct 12-month periods. The incidence of both menisci (ipsilateral knee) torn was 3.9%, and the ratio of medial to lateral meniscal tears was 2.7:1. Twelve percent of cases had tears of the anterior cruciate ligament, 70% of which were found with a concomitant medial meniscus tear. Arthrography was completely accurate in 73.2% of cases, and arthroscopy was accurate in 94.9%. When clinical impression, arthrography, and arthroscopy were combined, the overall diagnostic accuracy was 96.8%.