The sciatic nerve is part of the sacral plexus and it arises from the anterior rami of spinal nerves of L4 through S3.

The sciatic nerve is more precisely composed by:

1. The lumbosacral trunk that includes the nerves L4 and L5
2. Part of the Sacral Plexus that includes the nerves S1, S2, and S3

Sciatic Nerve Anatomy

The sciatic nerve runs down the posterior leg and it bifurcates into two terminal branches at the apex of the popliteal fossa:

1. Tibial Nerve ( formed by anterior division of spinal nerves L4-S3 )
2. Common Fibular Nerve ( formed by spinal nerves L4-S2 )

The Tibial Nerve innervations:

Posterior Compartment of the Tigh:

1. Semitendinosus Muscle
2. Semimembranous Muscle
3. Long Head of Biceps Femoris Muscle
4. Ischial part of Adductor Magnus Muscle

Posterior Compartment of The Leg:

1. Gastrocnemius Muscles
2. Plantaris Muscle
3. Soleus Muscle
4. Popliteus Muscle
5. Flexor Digitorum Longus
6. Tibialis Posterior
7. Flexor Allucis Longus Muscle

The Tibial Nerve divides into terminal branches:

1. Sural Nerve formed by fibers derived from spinal S1 and S2 nerves ( Nervus Suralis )
2. Medial Plantar NerveLateral Plantar Nerve
3. Medial Calcaneal Branch ( Rami Calcanei Mediales )

• Sensory Innervation to the lower posterolateral aspect of the leg and foot
• Motor Innervation of the foot’s muscles

The Common Fibular Nerve Innervations:

Posterior Compartment of the Tigh

1. Short Head of Biceps Femoris Muscle

Posterior Compartment of The Leg ( lateral Side of the Leg )

Superficial Fibular Nerve ( Nervus Fibularis Seperficialis )

1. Fibularis Longus Muscle
2. Fibularis Brevis Muscle

Deep Fibular Nerve ( Nervus Fibularis Profundus )

1. Tibialis Anterior Muscle
2. Extensor Allucis Longus Muscle
3. Extensor Digitorum Longus Muscle
4. Extensor Digitorum Brevis Muscle
5. Extensor Fibularis Tertius Muscle

The common Fibular Nerve, also known as a Common Peroneal Nerve provides sensory and motor innervations to the Posterolateral leg.

The Fibular Nerve divides into two terminal branches that innervate for the foot’s muscles:

1. Superficial Fibular Nerve that provides motor innervations to the lower leg’s muscles and foot:

• Fibularis Longus Muscle
• Fibularis Brevis Muscle
• Sensory innervation to the skin of the lower leg and dorsum of the foot

       2. Deep Fibular Nerve that provides motor and sensory innervations to the anterior compartment of the leg.

Anatomic Route of the sciatic nerve:

The Sciatic Nerve emerges from the pelvis below the piriformis muscle and lies on Gemellus Superior Muscle, Obturator Internus Muscle, Gemellus Inferior Muscle, and Quadratus Femoris Muscle.

It enters the thigh between the ischial tuberosity and the greater trochanter and goes down the back leg lying on the Adductor Magnus Muscle and surrounded by the Semimembranous Muscle, and Biceps Femoris Muscles.