Tarsal tunnel syndrome is a condition in which the posterior tibial nerve, or one of its branches, becomes compressed as it passes through a narrow space on the inside of the ankle known as the tarsal tunnel. Although it is far less common than plantar fasciosis, it is an important cause of chronic heel pain because its symptoms often mimic more familiar conditions. Many patients spend months being treated for plantar fasciitis before the true diagnosis is recognised.
The tarsal tunnel is formed by the bones of the ankle on one side and a strong ligament, called the flexor retinaculum, on the other. Passing through this confined space are the posterior tibial nerve, arteries, veins and several tendons. Any condition that increases pressure within the tunnel can irritate or compress the nerve, producing pain and neurological symptoms.
Unlike plantar fasciosis, which is a disorder of the plantar fascia, tarsal tunnel syndrome is a nerve compression disorder. As a result, patients often describe symptoms that are quite different from typical plantar heel pain. Burning, tingling, numbness, electric shock-like sensations or pain radiating into the arch, toes or sole of the foot are common. Some patients also experience a feeling that their foot is swollen or "full," even though there is little visible swelling.
The symptoms frequently worsen with prolonged standing or walking because these activities increase pressure around the nerve. Some patients also notice that the discomfort is worse at night or after spending many hours on their feet. Unlike plantar fasciosis, where pain often improves after the first few steps, nerve pain may become progressively more irritating as the day goes on.
Several different conditions can contribute to compression of the posterior tibial nerve. Flat feet may increase tension around the tarsal tunnel, while ganglion cysts, varicose veins, inflammation, previous ankle injuries, fractures, scar tissue or space-occupying lesions may directly compress the nerve. In many patients, however, no single cause is identified, and the condition develops gradually over time.
Tarsal tunnel syndrome may also coexist with other causes of heel pain. Patients sometimes have plantar fasciosis, Baxter's nerve entrapment or heel fat pad syndrome at the same time. This is one reason why some people experience only partial improvement after treatment directed at the plantar fascia. If nerve compression has not been recognised, the underlying source of pain remains untreated.
Diagnosing tarsal tunnel syndrome requires careful clinical assessment. The location of symptoms, the presence of burning or tingling, reproduction of symptoms when the nerve is examined and the pattern of pain all provide valuable clues. Diagnostic ultrasound may help identify ganglion cysts, tendon pathology or other soft tissue abnormalities contributing to nerve compression, while MRI may be useful when deeper structural pathology is suspected. In selected patients, nerve conduction studies may also assist the assessment, although normal studies do not completely exclude the diagnosis.
The treatment pathway differs from many other causes of heel pain. Management may include activity modification, footwear advice, treatment of underlying biomechanical abnormalities, orthotic therapy where appropriate and management of any structure compressing the nerve. In carefully selected patients, ultrasound-guided procedures or surgical decompression may be considered if conservative treatment fails.
The most important message is that persistent heel pain associated with burning, tingling or numbness should never automatically be assumed to be plantar fasciitis. Tarsal tunnel syndrome is an important differential diagnosis, and recognising it early allows treatment to be directed towards the compressed nerve rather than repeatedly treating the plantar fascia.