What is the primary function of the piriformis muscle?

The piriformis muscle is primarily responsible for the rotation and abduction of the thigh at the hip joint. This muscle originates from the anterior surface of the sacrum and inserts into the greater trochanter of the femur. When the hip is flexed, it aids in externally rotating the thigh, which is crucial for movements such as walking and running, allowing for better mobility and stability of the lower body.

The role of the piriformis in abduction also becomes evident when the hip is flexed at 90 degrees, as it assists in moving the thigh away from the midline of the body. This action is fundamental in various athletic activities and everyday movements.

While other options suggest functions related to the knee or flexing and extending the thigh, those actions are primarily associated with different muscle groups rather than the piriformis, which is dedicated to the rotational dynamics of the hip. Thus, the proper identification of the piriformis muscle’s function emphasizes its importance in hip stability and movement.