A test for diagnosing lesions to the lateral meniscus is described. Due to our inability to find its description in the literature we called it 'dynamic test'. The accuracy of this test was assessed in 421 knees. The test was compared against arthroscopic findings in all cases. Inter-rater reliability was also estimated among three observers, who were shown to have a K coefficient ranging from 0.61 to 0.85. In a series of healthy subjects, the test was positive in eight normal knees (9.4%), but none of these false-positives was unanimously identified by more than one rater. This manipulative test was very accurate: sensitivity 85%, specificity 90.3%, positive predictive value 73.2%, negative predictive value 95% prevalence 23.7% and accuracy 89%. Thus, the test seems to be a tool that can improve the diagnostic accuracy of meniscal lesions. An important feature of this test is that it can be performed in patients with acute injuries.