Posterior trunk bending during the stance phase of gait suggests weakness of which muscle on the same side?

• A. Gluteus maximus
• B. Adductors
• C. Iliopsoas
• D. Quadriceps

Answer: (A)

Posterior trunk bending during stance points to weakness of the hip extensor on that side, mainly the gluteus maximus. In late stance, this muscle drives hip extension to push the body forward. When it’s weak, the body compensates by bending the trunk backward (a hip extensor lurch), using the spine muscles to assist extension and keep the leg moving through stance. The other options don’t play the key role in producing this backward trunk lean: adductors mainly bring the leg toward the midline, iliopsoas is a hip flexor, and the quadriceps extend the knee.