Which of the following muscles is NOT involved in hip flexion?

The gluteus maximus is primarily involved in hip extension, not hip flexion. This powerful muscle is located at the back of the hip and is responsible for moving the thigh backward, especially when rising from a seated position, climbing stairs, or running.

In contrast, the other muscles listed—iliopsoas, sartorius, and rectus femoris—are all essential for the hip flexion movement. The iliopsoas is the primary hip flexor, consisting of the iliacus and psoas major muscles, while the sartorius assists with flexion, abduction, and external rotation of the hip. The rectus femoris, part of the quadriceps group, also contributes to hip flexion while working to extend the knee. Thus, identifying the gluteus maximus as not involved in hip flexion highlights its distinct role in hip movements, focusing on extension rather than flexion.