Trendelenburg sign interpretation: what does a pelvic drop on the unsupported side indicate?

Trendelenburg sign interpretation: what does a pelvic drop on the unsupported side indicate?

• A. Pelvic drop on unsupported side indicates hip adductor weakness.
• B. Pelvic drop on supported side indicates hip abductor weakness.
• C. Pelvic drop on unsupported side indicates hip abductor weakness.
• D. Pelvic drop with symmetry indicates normal knee function.

Answer: (C)

The main idea is hip abductor strength during single-leg stance. When you stand on one leg, the hip abductors on that stance leg (gluteus medius and minimus) contract to keep the pelvis level. If those abductors are weak, they can’t hold the pelvis up on the opposite side, so the pelvis drops toward the unsupported side. That drop indicates weakness of the hip abductors on the stance leg. So a pelvic drop on the unsupported side points to hip abductor weakness in the leg you’re standing on. Adductor weakness wouldn’t cause this pattern, a drop on the supported side isn’t the typical sign, and symmetry would suggest normal hip function rather than anything about the knee.

The main idea is hip abductor strength during single-leg stance. When you stand on one leg, the hip abductors on that stance leg (gluteus medius and minimus) contract to keep the pelvis level. If those abductors are weak, they can’t hold the pelvis up on the opposite side, so the pelvis drops toward the unsupported side. That drop indicates weakness of the hip abductors on the stance leg.

So a pelvic drop on the unsupported side points to hip abductor weakness in the leg you’re standing on. Adductor weakness wouldn’t cause this pattern, a drop on the supported side isn’t the typical sign, and symmetry would suggest normal hip function rather than anything about the knee.