Supporting, balancing, and propelling the body is the work of the muscular system of the legs and feet. From the large, strong muscles of the buttocks and legs to the tiny, fine muscles of the feet and toes, these muscles can exert tremendous power while constantly making small adjustments for balance — whether the body is at rest or in motion.
The powerful muscles of the hip, buttock, and pelvis actuate the flexible ball-and-socket hip joint. The anterior muscles, such as the quadriceps femoris, iliopsoas, and sartorius, work as a group to flex the thigh at the hip and extend the leg at the knee. Posterior muscles, such as the hamstrings and gluteus maximus, produce the opposite motion — extension of the thigh at the hip and flexion of the leg at the knee. Lateral muscles, such as the gluteus medius, abduct the thigh at the hip while the medial groin muscles adduct the thigh. All of these muscle groups provide powerful contractions to propel the body while making fine adjustments to maintain the body’s posture and balance.
Located inferior to the knee are a number of muscles that move the ankle, foot, and toes. The calf muscles, including the gastrocnemius and soleus, join to form the strong calcaneal (Achilles) tendon of the heel and attach to the calcaneus bone in the heel. These muscles contract to plantar flex the foot — such as when standing on your tiptoes — and flex the toes. Shin muscles, such as the tibialis anterior and extensor digitorum longus, dorsiflex the foot and extend the toes. The muscles of the calf also work subtly to stabilize the ankle joint and foot and to maintain the body’s balance.