Passive moment about the hip in straight leg raising.

OBJECTIVE: The purpose of this examine is to study the load-deformation characteristics of the hip in straight leg raising. DESIGN: An experimental study in which passive moment about the hip was determined as a function of hip angle. BACKGROUND: Straight leg raising is widely employed in clinical examination, and there is little information on its mechanical characteristics. METHODS: Fourteen healthy volunteers were recruited for this study. Three trials of straight leg raise tests were performed while subjects lay supine on a plinth that was fitted with load cells. An electrogoniometer was employed to measure hip flexion during the test. Resistive moment at the hip was determined using a dynamic biomechanical model. RESULTS: The present experimental method was shown to be highly reliable. The moment-angle curves of all subjects were shown to follow an exponential function. CONCLUSION: Stiffness and strain energy of posterior hip tissues could be derived from the moment-angle curves. Evaluation of such elastic properties is clinically important as they may be altered with injuries of the tissues. RELEVANCE: Clinically, contracture of hamstring muscles and other posterior hip tissues is evaluated by measuring the available range of hip flexion in straight leg raising. However, this does not provide any information on the elastic properties of the tissues. The present study reports a reliable method of evaluating such properties.