APPLIED RADIOLOGICAL ANATOMY

Detailed explanation-1: -During hip extension, the gluteus maximus and three muscles of the hamstrings play the role of main agonists, and the adductor maximus acts as a synergist. During hip flexion, the iliopsoas and rectus femoris are the main agonists, and the sartorius and adductor longus act as synergists.

Detailed explanation-2: -The iliopsoas muscle is the strongest hip flexor and assists in external rotation of the femur, playing an important role in maintaining the strength and integrity of the hip joint.

Detailed explanation-3: -The hip flexors consist of 5 key muscles that contribute to hip flexion: iliacus, psoas, pectineus, rectus femoris, and sartorius.

Detailed explanation-4: -Thus, the rectus femoris is used more during 0°–45° hip flexion, to induce anterior tilting and hip flexion of the pelvis, whereas rectus abdominis activation is used for hip flexion at 45° and greater, to induce hip flexion accompanied by posterior tilting of the pelvis.