Two muscles blend to form the iliopsoas group: the iliacus and the psoas major. The iliacus sits in the iliac fossa of the pelvis, while the psoas major runs along the lumbar spine. Their fibers merge into a single tendon that attaches to the lesser trochanter of the femur. This combination makes the iliopsoas the primary hip flexor, powerful for lifting the thigh toward the torso or, when the thigh is fixed, flexing the trunk. The other options involve muscles that don’t join to form the iliopsoas. The rectus femoris and vastus lateralis are part of the quadriceps and mainly extend the knee, with the rectus femoris also crossing the hip but not forming this group. The gluteus maximus and gluteus medius are located lateral/posterior to the hip and are mainly involved in hip extension and abduction. The tensor fasciae latae and sartorius are separate muscles with different roles, and they don’t blend to constitute the iliopsoas.