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The lateral rotator group is a group of six small muscles of the hip which all externally (laterally) rotate the femur in the hip joint.It consists of the following muscles: piriformis, gemellus superior, obturator internus, gemellus inferior, quadratus femoris and the obturator externus.
The gluteal muscles include the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae.They cover the lateral surface of the ilium.The gluteus maximus, which forms most of the muscle of the buttocks, originates primarily on the ilium and sacrum and inserts on the gluteal tuberosity of the femur as well as the iliotibial tract, a tract of strong fibrous tissue that runs ...
of thigh/femur at hip [2] Gluteus maximus; Lateral rotator group. piriformis; gemellus superior; obturator internus; pectineus ; gemellus inferior; obturator externus; quadratus femoris; Sartorius; of leg at knee [3] Biceps femoris; of eyeball (motion is also called "extorsion" or excyclotorsion) [4] Inferior rectus muscle; Inferior oblique muscle
The functions of muscles includes extension, abduction and internal as well as external rotation of the hip joint. The gluteus maximus also supports the extended knee through the iliotibial tract. The human gluteus maximus plays multiple important functional roles, particularly in running rather than walking.
As a short muscle around the hip joint, it stabilizes the hip joint as a postural muscle. [6] It also helps to abduct the hip joint when in flexion. [7] And it helps to stabilise the head of the femur in the socket during flexion and internal rotation as it's posterior fibers reinforce the posterior capsule of hip joint. [8]
However, its function changes in different positions of the femur. For example: If the leg is flexed, the whole muscle will flex. [5] The posterior fibres of gluteus medius contract to produce hip extension, lateral rotation and abduction. During gait, the posterior fibres help to decelerate internal rotation of the femur at the end of swing phase.
This causes the femur to rotate and point the knee laterally. The lateral rotators also oppose medial rotation by the gluteus medius and gluteus minimus. When the hip is flexed to 90 degrees, piriformis abducts the femur at the hip and reverses primary function, internally rotating the hip when the hip is flexed at 90 degrees or more. [7]
Located on the posterior side of the hip joint, it is a strong external rotator and adductor of the thigh, [2] but also acts to stabilize the femoral head in the acetabulum. The quadratus femoris is used in Meyer's muscle pedicle grafting to prevent avascular necrosis of femur head.