The pectineus muscle arises from the
pectineal line of the
pubis and to a slight extent from the surface of bone in front of it, between the
iliopectineal eminence and
pubic tubercle, and from the fascia covering the anterior surface of the muscle; the fibers pass downward, backward, and lateral, to be inserted into the
pectineal line of the femur which leads from the
lesser trochanter to the
linea aspera.
Relations The pectineus is in relation by its anterior surface with the pubic portion of the
fascia lata, which separates it from the
femoral artery and
vein and internal
saphenous vein, and lower down with the
profunda femoris artery. By its posterior surface with the
capsule of the hip joint, and with the
obturator externus and
adductor brevis, the
obturator artery and
vein being interposed. By its external border with the
psoas major, the
femoral artery resting upon the line of interval. By its internal border with the outer edge of the
adductor longus.
Obturator foramen is situated directly behind this muscle, which forms one of its coverings. It forms part of the floor of the
femoral triangle.
Innervation The lumbar plexus is formed from the anterior rami of nerves L1 to L4 and some fibers from T12. With only five roots and two divisions, it is less complex than the brachial plexus and gives rise to a number of nerves including the femoral nerve and accessory obturator nerve. The pectineus muscle is considered a
composite muscle as the innervation is by the
femoral nerve (L2 and L3) and occasionally (20% of the population) a branch of the
obturator nerve called the
accessory obturator nerve. When it is present, the accessory obturator nerve innervates a portion of the pectineus muscle, entering the muscle on its dorsomedial aspect. The greater nerve to the muscle is the femoral nerve. Unlike the obturator accessory nerve, the femoral nerve is always present and provides the sole innervation for the pectineus muscle in over 90% of cases. The muscle is also innervated by the accessory obturator nerve in the 8.7% of cases in which the nerve occurs. ==Function==