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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 .
When the legs open, such as in the lotus posture of yoga, this is called "lateral rotation", with the opposite movement called "medial rotation". Hip abduction occurs when the femur moves outward to the side, as in taking the thighs apart. Hip adduction occurs when the femur moves back to the midline. Many muscles contribute to these movements:
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
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]
The sartorius muscle can move the hip joint and the knee joint, but all of its actions are weak, making it a synergist muscle. [4] At the hip, it can flex, weakly abduct, and laterally rotate the femur. [4] At the knee, it can flex the leg; when the knee is flexed, sartorius medially rotates the leg.
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.
Gluteus Maximus: The gluteus maximus is primarily responsible for hip extension, external rotation, and helps maintain an upright posture. This muscle is a powerful hip extensor (meaning it brings ...
In human anatomy, the adductor minimus (adductor femoris minimus or adductor quartus) is a small and flat skeletal muscle in the thigh which constitutes the upper, lateral part of the adductor magnus muscle. [1] It adducts and laterally rotates the femur. [2]