A positive Trendelenburg test indicates weakness of which muscle?

• A. Gluteus medius
• B. Gluteus maximus
• C. Tensor fasciae latae
• D. Iliopsoas

Answer: (A)

The Trendelenburg test checks the strength of the hip abductors, especially the gluteus medius. When you stand on one leg, the pelvis should stay level, and the gluteus medius (and minimus) on that stance leg contracts to keep the pelvis from dropping on the opposite side. If these muscles are weak, the pelvis tilts downward on the unsupported side, producing a positive Trendelenburg sign. The gluteus maximus is mainly a hip extensor, the tensor fasciae latae is a smaller abductor/flexor with less stabilizing role, and the iliopsoas is a hip flexor. Thus, weakness of the gluteus medius best explains the observed sign.