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The lumbar plexus (T12–L5) (see Fig. 21.1)
eous branches, which supply the skin over the anterior and medial
See Chapter 21.
aspects of the thigh, and two muscular branches. The latter supply
• Origins: from the anterior primary rami of T12–L5.
sartorius and pectineus.
• Course: the majority of the branches of the plexus pass through the • Superficial divisionaconsists of medial and intermediate cutan-
substance of psoas major and emerge at its lateral border except for the • Deep divisionaconsists of four muscular branches which supply
genitofemoral and obturator nerves. the components of quadriceps femoris and one cutaneous nervea
• Branches: the saphenous nerve. The latter nerve is the only branch to extend
• Intra-abdominal branchesathese are described in Chapter 21. beyond the knee. It pierces the deep fascia overlying the adductor
• Femoral nerve (L2,3,4)asee below. canal and descends through the leg, accompanied by the great
• Obturator nerve (L2,3,4)asee below. saphenous vein, to supply the skin over the medial aspect of the leg
• Lateral cutaneous nerve of the thigh (L2,3)acrosses the iliac and foot.
fossa over iliacus and passes under the lateral part of the inguinal
ligament to enter the superficial tissue of the lateral thigh which it The obturator nerve (L2,3,4) (Fig. 44.2)
supplies. Obese patients sometimes describe paraesthesiae over the • Origins: the anterior divisions of the anterior primary rami of
lateral thigh. This is termed meralgia paraesthetica and results from L2,3,4.
compression of this nerve as it passes under the inguinal ligament. • Course: the obturator nerve emerges at the medial border of psoas
(cf. other nerves which traverse psoas to emerge at the lateral border).
The femoral nerve (L2,3,4) (Fig. 44.1) It passes over the pelvic brim to pass through the upper aspect of the
• Origins: the posterior divisions of the anterior primary rami of obturator foramen with other obturator vessels. In the obturator notch
L2,3,4. it divides into anterior and posterior divisions which pass in front
• Course: the femoral nerve traverses psoas to emerge at its lateral of and behind adductor brevis to supply the muscles of the adductor
border. It descends through the iliac fossa to pass under the inguinal compartment:
ligament. At this point it lies on iliacus, which it supplies, and is situ- • Anterior divisionagives rise to an articular branch to the hip joint
ated immediately lateral to the femoral sheath. It branches within the as well as muscular branches to adductor longus, brevis and gra-
femoral triangle only a short distance (5 cm) beyond the inguinal liga- cilis. It terminates by supplying the skin of the medial aspect of the
ment. The lateral circumflex femoral artery passes through these thigh.
branches to divide them into superficial and deep divisions: • Posterior divisionasupplies muscular branches to obturator
externus, adductor brevis and magnus and obturator externus as
well as an articular branch to the knee.

The nerves of the lower limb I 99