Tarsal Tunnel Syndrome
Tarsal tunnel syndrome is a compression, or squeezing, on the posterior tibial nerve that produces symptoms anywhere along the path of the nerve running from the inside of the ankle into the foot.
The tarsal tunnel is a narrow space that lies on the inside of the ankle next to the ankle bones. The tunnel is covered with a thick ligament (the flexor retinaculum) that protects and maintains the structures contained within the tunnel—arteries, veins, tendons and nerves. One of these structures is the posterior tibial nerve, which is the focus of tarsal tunnel syndrome.
Tarsal tunnel syndrome is similar to carpal tunnel syndrome, which occurs in the wrist. Both disorders arise from the compression of a nerve in a confined space.
Tarsal tunnel syndrome is caused by anything that produces compression on the posterior tibial nerve:
• A person with flat feet is at risk for developing tarsal tunnel syndrome, because the outward tilting of the heel that occurs with fallen arches can produce strain and compression on the nerve.
• An enlarged or abnormal structure that occupies space within the tunnel can compress the nerve. Some examples include a varicose vein, ganglion cyst, swollen tendon or arthritic bone spur.
• An injury, such as an ankle sprain, may produce inflammation and swelling in or near the tunnel, resulting in compression of the nerve.
• Systemic diseases, such as diabetes or arthritis, can cause swelling, thus compressing the nerve.