What is the primary action that does NOT occur at the hip when the piriformis contracts?

The correct choice is adduction, as the primary action that does not occur at the hip when the piriformis muscle contracts. The piriformis is primarily known for its role in lateral rotation of the hip when the hip is extended and can also assist in the abduction of the hip when the hip is flexed.

In contrast, adduction refers to drawing the leg towards the midline of the body, which is not a function of the piriformis. Instead, other muscles, such as the adductor group, are responsible for that movement.

Flexion, internal rotation, and extension can occur to varying degrees with the assistance of the piriformis muscle depending on the positioning of the hip. Thus, acknowledging the specific functions of the piriformis in relation to hip movement helps clarify why adduction is the action that does not involve this particular muscle when it contracts.