Dr. Reiman is an active clinical researcher, an educator within Duke University's Physical Therapy Division.
In an article written for the British Journal of Sports medicine (bjsm.bmj.com) Dr. Reiman has undertaken a systematic review and meta-analysis of clinical tests of the hip (http://bjsm.bmj.com/content/early/2012/07/07/bjsports-2012-091035), and in these series of videos he will demonstrate some of these techniques.
In this video he demonstrates the Thomas test. A click and/or catch is a positive result for this test, and indicates a labral tear.