COMLEX USA Comprehensive Osteopathic Medical Licensing Examination Practice 2026 - Free COMLEX Practice Questions and Study Guide

The Trendelenburg test is specifically designed to assess the function of the gluteus medius muscle. This muscle plays a critical role in stabilizing the pelvis during single-leg stance. When a person stands on one leg, the gluteus medius on the side of the standing leg should contract to keep the pelvis level. If there is weakness or dysfunction in the gluteus medius, there will be a noticeable drop of the pelvis on the opposite side, indicating positive Trendelenburg sign.

The other muscles listed, such as the psoas, quadriceps, and tibialis anterior, are not primarily involved in this specific stability function during the Trendelenburg test. The psoas is more associated with hip flexion, the quadriceps with knee extension and support, and the tibialis anterior with dorsiflexion of the foot. Therefore, assessing the gluteus medius directly correlates with the mechanics that the Trendelenburg test is meant to evaluate.