The sartorius- named somewhat erroneously from sartor, a tailor, because it has been supposed to be the muscle by which the cross-legged sitting posture is produced- is a long, ribbon- shaped muscle slightly fusiform at the two ends.

Origin

The anterior superior spine of the ilium and the adjacent part of the lotch between this process and the anterior inferior spine.

Insertion

1. The front part of the inner surface of the tibia, just internal to the tubercle;
2. the upper part of the deep fascia covering the internal surface of the leg.

Structure

Arising by short tendinous fibers, the fleshy fibers which are the longest in the whole body, run parallel to one another inwards and downwards cross the front of the thigh and after reaching the inner surface of the thigh about the middle, the muscular band runs almost vertically downwards to the back of the internal condyle of the femur. At this point the tendon of insertion makes its ppearance as an aponeurosis which covers the deep aspect of the muscle and becomes free from fleshy fibers just below the knee joint, where it turns forwards and covers the inner surface of the inner tuberosity of the tibia, being separated fom it as well as from the tendons of the gracilis and semi-tendinosus by a large bursa. The upper border of this aponeurosis is thick and tendinous and is inserted directly into the bone. The lower part of the aponeurosis, which is of a much more membranous character, is continued downwards and forwards and blends with the deep fascia of the inner side of the leg, of which it is one of the chief constituents.

Nerve-supply

From the second, third and fourth branches of the lumbar lexus, by filaments which are usually derived from the middle cutaneous branch of the anterior crural nerve as it pierces the muscle at the junction of its middle and upper thirds.

Action

1. To flex the thigh and at the same time rotate it slightly outwards and abduct it.
2. To flex the knee and when the knee is in the bent position it will also help in rotating the leg inwards.
3. Being contained in the close-fitting sheath formed by the fascia lata and its deep processes, it will tend when it contracts to draw the soft parts upon the inner surface of the thigh forwards and so make tense the inner portion of the fascia lata.
4. Acting from below, it will flex the pelvis upon the thigh.

Relations

In front above lies the fascia lata; internally below lie the fascia lata and internal saphenous vein; beneath lie the rectus femoris, iliacus, pectineus, adductor longus and magnus, vastus internus and the inner hamstring tendons, the femoral vessels, the anterior crural nerve and its internal saphenous and vastus internus branches.

Variations

The sartorius is occasionally absent; it may also be divided longitudinally. It may have insertions into the fascia lata, or the ligamentmn patellae. A tendinous intersection sometimes crosses the muscle.

Muscles of the front of the thigh.