The Trendelenburg sign indicates weakness in specific hip muscles. It is a physical manifestation seen during standing or walking, not a disease. It provides a clue that pelvic stabilizing muscles may not be functioning correctly, suggesting an underlying issue that warrants further medical investigation.
Recognizing the Sign
A positive Trendelenburg sign is most apparent during single-leg stance. As the individual stands on one leg, the pelvis on the unsupported side (the lifted leg) visibly drops or tilts downward. This drop occurs because the muscles on the standing leg cannot adequately stabilize the pelvis. During walking, this imbalance can lead to a characteristic “waddling” or lurching gait, where the body shifts excessively over the weight-bearing leg to compensate for the pelvic instability.
The Underlying Cause
A positive Trendelenburg sign primarily results from weakness in the hip abductor muscles: the gluteus medius and gluteus minimus. Located on the side of the hip, these muscles move the leg away from the body’s midline (abduction) and stabilize the pelvis during single-leg support. When standing on one leg, these muscles on the supporting side contract to prevent the pelvis from dropping on the opposite side. Weakness can stem from direct muscle injury (e.g., tears) or damage to the superior gluteal nerve, which innervates both gluteus medius and minimus.
The Trendelenburg Test
Healthcare professionals use the Trendelenburg test to assess for this sign. The test involves asking the patient to stand on one leg for a short period. The clinician observes the patient’s pelvis from behind. A positive result occurs if the pelvis on the side of the lifted leg drops below the standing leg’s hip. This test serves as a clinical tool to identify hip abductor weakness, a key indicator for various hip dysfunctions.
Implications and Next Steps
Recognizing the Trendelenburg sign indicates a functional impairment that can affect walking, balance, and daily activities. This muscular weakness can contribute to abnormal gait patterns and increase the risk of falls. A positive Trendelenburg sign warrants medical evaluation to pinpoint the underlying cause of hip abductor weakness. Depending on the diagnosis, management may involve physical therapy to strengthen affected muscles or other interventions to address the root of the problem.