Origin and Insertion
- Origin (O): arises from the anterior superior iliac spine (spina iliaca anterior superior).
- Course: runs obliquely downward and medially across the anterior aspect of the thigh, transitioning to the anterior-medial aspect of the knee joint.
- Insertion (I): attaches medially to the tibial tuberosity. At this site, its tendon merges with the tendons of the gracilis (m. gracilis) and semitendinosus (m. semitendinosus) muscles to form a conjoined tendon known as the pes anserinus («goose's foot»). Two to three subtendinous bursae of the sartorius are typically found near the insertion site.
Functions
- Flexion: flexes the hip and flexes the leg at the knee joint.
- Rotation and Abduction: abducts and laterally rotates the thigh. When the knee is flexed, it medially rotates the leg.
- Complex Movements: due to its multi-joint actions, the muscle assists in crossing the legs (sitting cross-legged).
Blood Supply and Innervation
- Innervation (N): supplied by the femoral nerve (n. femoralis, spinal segments L2–L3).
- Blood Supply: supplied by branches of the femoral artery (a. femoralis), the lateral circumflex femoral artery (a. circumflexa femoris lateralis), and the descending genicular artery (a. descendens genus).
Topography and Relations
- Fascial Compartment: the muscle is enclosed within an isolated fascial sheath formed by the fascia lata, with its superficial layer being particularly dense. The sartorius lies medial to the tensor fasciae latae (m. tensor fasciae latae).
- Relation to the Adductor Canal: the sartorius forms the roof of the adductor canal (Hunter's canal, canalis adductorius). Directly deep to the sartorius, the saphenous nerve (n. saphenus) and descending genicular vessels (a. et v. descendens genus) emerge through the anterior opening in the septum intermusculare vastoadductoria.
- Subcutaneous Layer: superficial to the fascia in this region, subcutaneous tissue contains the great saphenous vein (v. saphena magna). Anterior cutaneous branches of the femoral nerve (rr. cutanei anteriores n. femoralis) pierce the fascia along the medial border of the sartorius.
- Cross-Section: in the upper third of the thigh, the muscle is visualized within the anterior compartment alongside the rectus femoris and vasti muscles.
Clinical Significance
- Surgical Landmark: the medial border of the m. sartorius and the superior aperture of the adductor canal serve as key surgical landmarks for accessing the femoral artery (a. femoralis) during bypass procedures.
- Neurological Evaluation: sartorius muscle strength is assessed using the MRC (Medical Research Council) scale to detect weakness in mononeuropathies.
- Pain Syndromes: inflammation of the anserine bursa (bursa anserina), located near the muscle's insertion, is a common cause of medial knee pain.