What is the Trendelenburg sign and what does it indicate?

• A. Pelvic drop of the unsupported side during single-leg stance; indicates weakness of the hip abductors (gluteus medius/minimus)
• B. Knee buckling
• C. Dorsiflexion weakness
• D. Anterior pelvic tilt due to hip flexor tightness

Answer: (A)

The Trendelenburg sign reflects weakness of the hip abductors, specifically the gluteus medius and minimus, and it shows up as a pelvic drop on the side opposite the standing leg during a single-leg stance. Normally these abductors keep the pelvis level in the frontal plane when you bear weight on one leg. If they’re weak, they can’t hold the pelvis up, so the unsupported side sags downward. This indicates impaired hip abductor function on the stance leg and is often observed in gait as a Trendelenburg pattern, where the pelvis drops on the swing-side during walking and the trunk may lean toward the stance leg to compensate. The other descriptions refer to different problems (knee instability, dorsiflexion weakness, or anterior pelvic tilt from tight hip flexors) and don’t capture the specific pelvis stabilization role of the hip abductors.