The Nerves of the lower limb originate from ventral (anterior primary) rami of the lumbar and sacral nerves while creating the lumbar plexus (L1-L4) in the posterior abdominal wall and the sacral plexus (l4-S4) in the pelvis.
The primary nerves of the lower limb are as follows:
- Femoral nerve.
- Obturator nerve.
- Sciatic nerve.
- Tibial nerve.
- Common peroneal nerve.
- Superficial peroneal nerve.
- Deep peroneal nerve.
Femoral Nerve is the main nerve of anterior compartment of thigh. It originates from the dorsal sections of the anterior primary rami of L2, L3, L4 nerves and is the largest branch of lumbar plexus. It goes into the thigh behind the inguinal ligament and lateral to femoral sheath while descending via psoas major and appearing on its lateral order between psoas and illiacus.
It digs into posterior and anterior section in femoral triangle 2 cm distal to the inguinal ligament. The lateral circumflex femoral artery is straddled by both sections. The illiacus in the abdomen and all the muscles of anterior compartment of the thigh is supplied by motor branches of it. The large cutaneous area on the anterior and medial part of thigh, medial side of leg and foot is supplied by the cutaneous branches of femoral artery. Hip and knee joints are also supplied by its articular branches.
Obturator Nerve belongs to the adductor compartment of the thigh. The inside of psoas major from anterior sections of the ventral rami of L2 to L4 spinal nerves. The nerve goes down in psoas major and issues from its medial border at the ala of the sacrum. It runs through the upper anterior part of the obturator foramen to the medial (adductor) compartment of the thigh while descending along the lateral wall of the lesser pelvis on the obturator internus.
It divides into anterior and posterior which stride the adductor brevis muscle, close to the obturator foramen. All muscles of the adductor compartment of thigh are supplied by its motor branches. Cutaneous area on the lower-half of the medial aspect of thigh are supplied by its sensory branches. Articular branches to the hip and knee joints are also supplied by it.
Sciatic Nerve is the thickest nerve in the body. At the beginning it is 1.5 to 2 cm wide. It is composed of 2 parts tibial and common peroneal nerves and its point of origin is in pelvis of ventral rami of L4 to S3 spinal nerves.
It goes into the gluteal region while, leaving the pelvis via greater sciatic foramen below piriformis. Here along the back of the thigh, it descends between the greater trochanter and ischial tuberosity. A little above the popliteal fossa (junction of middle and lower thirds of the thigh), it breaks up into terminal tibial and common peroneal nerves.
Tibial Nerve is a large branch of the Sciatic nerve. The point of origin is above the popliteal fossa and goes downward respectively through middle of popliteal fossa and posterior compartment of leg and afterwards goes into sole of foot by passing deep to the flexor retinaculum where it divides into medial and lateral plantar nerves.
All the muscles of the posterior compartment of the leg are directly supplied by its motor, medial and its terminal branches, medial and lateral nerves supply all the muscles of lone. The whole skin of the sole of the foot and toes including all the dorsal parts of their last phalanges are supplied by its sensory branches through medial and lateral plantar nerves.
The tibial nerve goes under the tendinous arch created between the fibular and tibial heads of the soleus muscle and goes vertically through the deep region of the posterior compartment of the leg on the surface of the tibialis posterior muscle with the posterior tibial vessels.
Common Peroneal Nerve
Common Peroneal Nerve is a small terminal branch of the Sciatic nerve. Its point of appearance is just above popliteal fossa in the lower third of thigh. The entrance point in popliteal fossa is just below biceps tendon’s border along with upper lateral boundary of popliteal fossa . Then it goes over lateral head of gastrocnemius and plantaris. Afterwards it divides into two farthest branches the deep and superficial peroneal nerves when it twists around the lateral part of neck of fibula to reach deeper to peroneous longus while going over fibular connection of the soleus.
Superficial Peroneal Nerve
Superficial Peroneal Nerve is the nerve of the lateral compartment of the leg. It is 1 of the 2 terminal branches of the common peroneal nerve given in the neck of the fibula. The point of origin is in the substance of peroneus longus on the lateral side of the neck of fibula.
Its starting point is on the lateral side of the neck of the fibula and descends for a small space between the peroneus longus and peroneus brevis, and after that is located in a groove between the peroneus brevis and extensor digitorum longus.
At the junction of the upper 2/3rd and lower 1/3rd of the leg, it pierces the deep fascia, and shortly divides up into a medial and a lateral terminal branch which reaches the dorsum of the foot.
Deep Peroneal Nerve
Deep Peroneal Nerve is a nerve that is found in anterior compartment of leg and dorsum of the foot. It is corresponding to the posterior interosseous nerve of the forearm.
It’s one of the two terminal branches of the common peroneal nerve in the neck of the fibula.