🧠 Nervous System🟢 BasicPeripheral Nerves

The Sciatic Nerve

The largest nerve in the body, which supplies the back of the thigh and, through its branches, most of the leg and foot, and is vulnerable to injury in the buttock.

Key points

The sciatic nerve is the thickest nerve in the body, formed from the lower part of the lumbosacral plexus (roots L4 to S3).
It leaves the pelvis through the greater sciatic foramen, usually below the piriformis muscle, and runs down the back of the thigh.
It is really two nerves bound together, the tibial and the common fibular (peroneal), which usually separate just above the knee.
In the thigh it supplies the hamstring muscles, and through its two divisions it supplies all the muscles below the knee.
A badly placed injection into the buttock can injure it, so intramuscular injections use the safer ventrogluteal site, or the upper outer quadrant, to stay clear of the nerve.
Damage causes weakness of knee flexion and of everything below the knee, with loss of sensation over most of the leg and foot.

Memory trick

Two nerves in one sheath: the sciatic (L4 to S3) leaves below piriformis and splits into tibial and common fibular; injections use the ventrogluteal (or upper-outer) site to spare it.

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🧠 Nervous System🟢 BasicPeripheral Nerves

The Sciatic Nerve

The largest nerve in the body, which supplies the back of the thigh and, through its branches, most of the leg and foot, and is vulnerable to injury in the buttock.

Key points

The sciatic nerve is the thickest nerve in the body, formed from the lower part of the lumbosacral plexus (roots L4 to S3).
It leaves the pelvis through the greater sciatic foramen, usually below the piriformis muscle, and runs down the back of the thigh.
It is really two nerves bound together, the tibial and the common fibular (peroneal), which usually separate just above the knee.
In the thigh it supplies the hamstring muscles, and through its two divisions it supplies all the muscles below the knee.
A badly placed injection into the buttock can injure it, so intramuscular injections use the safer ventrogluteal site, or the upper outer quadrant, to stay clear of the nerve.
Damage causes weakness of knee flexion and of everything below the knee, with loss of sensation over most of the leg and foot.

Memory trick

Two nerves in one sheath: the sciatic (L4 to S3) leaves below piriformis and splits into tibial and common fibular; injections use the ventrogluteal (or upper-outer) site to spare it.

All of Anatomy More Nervous System