Leg adduction is the action at the hip joint that causes the legs to draw together or a single leg to pull in laterally from a side-lifted position. Its opposing movement is abduction, in which the legs are spread apart or a single leg is raised sideways at the hip joint. Both motions are performed in a side-to-side plane of movement known as the frontal plane. Examples of body movements that incorporate adduction include jumping jacks, ice skating, and the side-shuffling motion required by sports like tennis and basketball. Leg adduction is made possible by several muscles that cross the hip joint, especially by the adductor group found along the inner thigh: the adductor magnus, longus, and brevis, the pectineus, and the gracilis.
An action that is possible at the shoulder, wrist, and several of the hand joints as well as the hip joint, adduction can be performed by three joint types. Condyloid joints like that at the wrist feature ellipsoidal or oval-shaped bones that can curve about each other to produce a side-to-side tilting motion. Saddle joints like that at the base of the thumb produce the same movements, only the articulating bones, which resemble two saddles placed perpendicularly to one another with their concave surfaces facing inward, curve about each other. The hip joint, which produces leg adduction, is a ball-and-socket joint, a joint type that is capable of a large range of motion as the head of one bone spins and tilts freely within the socket of another bone.
Though not by a lack of mobility in the hip joint, the range of motion for leg adduction is limited. Where the motion finishes it is limited by one leg meeting the other at the midline of the body and where it begins it is limited by the flexibility of the inner thigh muscles. This is because adduction follows abduction, a motion that is permitted by the adductor muscles as they stretch to allow the opposing abductor muscles to lift the leg sideways. Then, to adduct the leg or pull it back toward the midline of the body, the adductor muscles must contract or shorten.
Five muscles of the inner thigh are responsible for leg adduction. The adductor magnus, adductor longus, and adductor brevis are the prime movers; these are assisted by the pectineus and gracilis. All five originate on the lower pelvis to the inside of the hip joint, and they extend obliquely in a fan shape to attach along the medial or inner surface of the femur bone in the thigh. Some like the pectineus and adductor brevis are short and narrow, inserting near the top of the inner thigh, while the adductor magnus attaches along the bone’s entire length, ending just above the knee.