Instrumental straight-leg raising: results in patients

Straight-leg raising is used as a diagnostic test for both elastogenic (passive muscle stretch test) and nonelastogenic (Lasègue's test) pathology in patients unable to bend forward from the standing position while holding the knees in extension. The test assessment is based on the range of the leg excursion and the type of pain that is provoked. An instrumental version of Lasègue's test (instrumental straight-leg raising) provides information about the extensibility, elasticity and electrical activity of the hamstrings and back muscles and about pelvic rotation. To investigate the diagnostical value of the additional information, both clinical and instrumental straight-leg raising was done by 30 patients who were unable to touch the ground while bending forward from the standing position with the knees extended. In one group of patients, the electrical activity of the muscles was comparable to that observed in the muscles of a control group of healthy volunteers; in a second group, however, the electrical muscle activity was aberrant. Muscle extensibility and passive muscle elasticity was comparable in patients in the first group and the healthy controls. In the patients with aberrant muscle activity, the elasticity of the passive muscles was not different from the control group, but both leg excursion and muscle extensibility were much smaller. Comparison of the clinically and experimentally diagnosed cause (elastogenic or non-elastogenic) of the movement restriction showed a remarkable discrepancy. We conclude that instrumental straight-leg raising provides valuable additional diagnostical information.