Which structure is closely associated with the piriformis muscle?

The sciatic nerve is closely associated with the piriformis muscle, making it the correct answer. The piriformis muscle originates from the anterior surface of the sacrum and inserts into the greater trochanter of the femur. It plays a crucial role in lateral rotation of the hip and can be involved in conditions such as piriformis syndrome, where the sciatic nerve may get compressed by the muscle.

The sciatic nerve typically runs beneath the piriformis muscle, but in some individuals, it may even pierce through the muscle itself. This anatomical relationship is significant in surgery and in the context of diagnosing conditions affecting hip and lower limb function.

The other options are not directly related to the piriformis muscle. The abdominal aorta is involved in supplying blood to the abdomen and lower limbs but is not anatomically associated with the piriformis muscle. The femoral nerve primarily innervates the anterior compartment of the thigh and does not have a close association with the piriformis. Meanwhile, the common peroneal nerve is a branch of the sciatic nerve that runs more laterally in the leg and is not directly linked to the function or structure of the piriformis muscle.