Which muscle groups are considered two-joint hip flexors?

• A. Gracilis and sartorius
• B. Quadriceps and gluteus maximus
• C. Iliopsoas
• D. Biceps femoris

Answer: (C)

The iliopsoas is considered the primary two-joint hip flexor because it consists of the psoas major and iliacus muscles, which originate in the lumbar region and pelvis, respectively, and insert at the lesser trochanter of the femur. Its function is to flex the hip, pulling the thigh toward the body while also assisting with internal rotation. This muscle group operates across two joints: the hip joint and the lumbar spine, allowing for flexion not just at the hip, but also contributing to flexion of the trunk at the lumbar spine.

In contrast, the other options do not meet the criteria for two-joint hip flexors. Gracilis and sartorius do cross two joints (hip and knee) but are not primarily hip flexors in the same capacity as the iliopsoas. The quadriceps group, including the rectus femoris, primarily serves as knee extensors and, although the rectus femoris crosses the hip joint and can assist in flexion, it is not considered a principal hip flexor. The biceps femoris, part of the hamstring group, primarily functions in knee flexion and hip extension, contradicting the role of a hip flexor entirely. Hence, the