Legs And Glutes
Legs And Glutes
The hip joint is one of the most flexible joints in the entire human body. The many muscles of the hip provide movement, strength, and stability to the hip joint and the bones of the hip and thigh. These muscles can be grouped based upon their location and function. The four groups are the anterior group, the posterior group, adductor group, and finally the abductor group. The anterior muscle group features muscles that flex (bend) the thigh at the hip. These muscles include: The iliopsoas group, which consists of the psoas major and iliacus muscles. The quadriceps femoris group, which consists of the rectus femoris, vastus intermedius, vastus lateralis, and vastus medialis. Sitting up, kicking a ball, and lifting a leg to climb a ladder are all activities that involve contraction of the anterior muscle group. The posterior muscle group is made up of the muscles that extend (straighten) the thigh at the hip. These muscles include the gluteus maximus muscle (the largest muscle in the body) and the hamstrings group, which consists of the biceps femoris, semimembranosus, and semitendinosus muscles. Climbing stairs, standing, walking, and running are all activities that require strong contractions from the posterior muscle group to extend the leg. The adductor muscle group, also known as the groin muscles, is a group located on the medial side of the thigh. These muscles move the thigh toward the body’s midline. Included in this group are the adductor longus, adductor brevis, adductor magnus, pectineus, and gracilis muscles. Overstretching of these muscles caused by rapid lateral movement the thigh can lead to a groin pull, a common sports injury. The abductor muscle group is located on the lateral side of the thigh and moves the thigh away from the body’s midline. These muscles include the piriformis, superior gemellus, inferior gemellus, tensor fasciae latae, sartorius, gluteus medius, and gluteus minimus muscles. Spreading the legs to do a split is an example of a movement involving the abductor muscles.
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.
The long head of biceps femoris muscle originates from the lower end of the ischium to cross the front of the knee and insert on the tibia and fibula. As the name implies, the biceps femoris has two heads, or immovable ends, one attached to the ischium (bone in the pelvis) and the other attached to the femur (thigh bone). The muscle passes along the back of the thigh on the lateral side and connects close to the midline ends of the fibula and tibia (bones in the lower leg). The biceps femoris is one of the hamstring muscles, and its tendon (hamstring) can be felt as a ridge behind the knee. This muscle functions to flex and rotate the leg laterally and to extend the thigh.
The semitendinosus muscle is another of the hamstring muscles. It is a long, band-like muscle on the back of the thigh toward the inside, connecting the ischium to the proximal end of the tibia. It is so named because it becomes tendinous in the middle of the thigh, continuing to its movable end as a long, cord-like tendon. It functions to flex and rotate the leg medially and to extend the thigh.
The gastrocnemius muscle is the most superficial and prominent of the calf muscles. It is made of two muscular regions, the medial head and lateral head, which attach to the medial and lateral sides of the femur. The heads of the gastrocnemius muscle work together to plantarflex the foot at the ankle and to flex the leg at the knee. The medial head of the gastrocnemius is a large, muscular belly located on the medial side of the calf next to the almost identical lateral head of the gastrocnemius. It is a superficial muscle, making it easy to palpate through the skin of the calf while pointing one’s toes. Deep to the gastrocnemius are the soleus and plantaris muscles. The medial head of the gastrocnemius muscle arises from the medial condyle of the femur just distal and medial to the popliteal fossa. From its origin it passes posterior to the knee joint and descends the leg parallel to the lateral head of the gastrocnemius. At about the middle of the calf, both heads merge together to form the calcaneal tendon, which is more commonly known as the Achilles tendon. The calcaneal tendon continues distally toward the ankle, where the soleus and plantaris muscles join the tendon. After passing posterior to the ankle joint, the calcaneal tendon inserts to the calcaneus, or heel bone.
The gastrocnemius muscle crosses both the knee joint and the ankle joint, giving it a distinct function at each joint. At the ankle joint, the gastrocnemius pulls on the calcaneal tendon and calcaneus to plantarflex the ankle. Plantarflexion is a specific movement at the ankle, which moves the sole of the foot posteriorly and points the toe. The soleus and plantaris muscles, which also form the calcaneal tendon, assist the gastrocnemius in this motion, but the gastrocnemius is by far the most powerful plantarflexor. At the knee joint, the gastrocnemius pulls the calcaneus posteriorly toward the posterior of the femur, flexing the knee. The three hamstring muscles also work with the gastrocnemius to perform knee flexion.