Tibial nerve dysfunction is a form of peripheral neuropathy. It occurs when there is damage to the tibial nerve, one of the branches of the sciatic nerve of the leg. It innervates (stimulates) the calf muscles (hamstrings) and muscles that allow the foot to bend (foot flexors). It supplies sensation to the bottom of the foot.

Dysfunction of a single nerve group, such as the tibial nerve is classified as mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although occasionally systemic disorders may cause isolated nerve damage (such as occurs with mononeuritis multiplex).

The usual causes are direct trauma (for example, after an intramuscular injection), prolonged pressure on the nerve, and compression of the nerve from nearby body structures. Entrapment involves pressure on the nerve where it passes through a narrow structure.

The damage includes destruction of the myelin sheath of the nerve or destruction of part of the nerve cell (the axon). Damage to the axon slows or prevents conduction of impulses through the nerve.

The tibial nerve is commonly injured by fractures or other injury to the back of the knee or the lower leg. It may be affected by systemic diseases causing polyneuropathy (damage to multiple nerves) such as diabetes mellitus or polyarteritis nodosa. It may be damaged by pressure from lesions such as tumor, abscess, or bleeding into the knee.

In some cases, no detectable cause can be identified. The mechanical factors may be complicated by ischemia (lack of oxygen from decreased blood flow) in the area.