What is the primary muscle involved in hip flexion?

The primary muscle involved in hip flexion is the psoas major. This muscle plays a crucial role in lifting the thigh towards the torso, which is the action of hip flexion. The psoas major originates from the lumbar vertebrae and inserts into the femur, functioning effectively in movements that require bending at the hip joint, such as climbing stairs, running, and walking.

While other muscles contribute to hip flexion, the psoas major is particularly essential due to its anatomical position and leverage in facilitating this movement. The quadriceps, primarily known for their role in knee extension, do not primarily function in hip flexion. The hamstrings, located at the back of the thigh, primarily function in hip extension and knee flexion. The gluteus maximus, one of the largest muscles in the body, plays a significant role in hip extension and external rotation, rather than flexion. Therefore, the psoas major stands out as the key muscle driving hip flexion.