Tarsal tunnel syndrome

Tarsal tunnel syndrome is a pinched nerve at your ankle. The tibial nerve runs down the inside of your ankle through a narrow canal made by bone on one side and a tough fibrous band on the other (the tarsal tunnel). Squeeze that nerve and you get the symptoms. It's the foot's version of carpal tunnel. The squeeze can come from a cyst, a fatty growth, or a varicose vein taking up space in the canal; from a flatfoot pulling the nerve into a stretched position; from scar tissue after an old ankle injury; or sometimes from no obvious cause at all.

The classic symptoms are burning, tingling, or numbness on the bottom of the foot — often worse at night or after long stretches of standing.

Your provider taps lightly behind the bony bump on the inner side of your ankle — if that reproduces the tingling down into the foot, that's a positive Tinel's sign. Nerve-conduction studies (NCS/EMG) confirm the diagnosis and tell us how severely the nerve is being squeezed. MRI or ultrasound looks for a cyst or other space-taking lesion in the tunnel. Tarsal tunnel is one of those diagnoses that gets both over-called and missed — careful NCS interpretation and a thoughtful exam matter.

When NCS confirms the nerve is compressed and there's a clear space-occupying lesion to remove, or when months of bracing and injections haven't quieted the symptoms, surgical decompression is the answer. The procedure opens the fibrous band over the nerve to give it more room, and removes any cyst or lesion that's pressing on it.

External patient-education references and related OSI pages for additional background:

• Britannica — Ankle (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language