A 68-year-old woman is reviewed six weeks after a right hip replacement performed through a lateral approach. She walks with her trunk lurching to the right. When she stands on the right leg alone, the left side of the pelvis drops. She rises from a low chair and climbs stairs without difficulty. Hip adduction and knee extension are full, and she can walk on her heels and toes.
Damage to which one of the following nerves best explains this woman's lurching gait and the drop of her pelvis?