How Is Tarsal Tunnel Syndrome Diagnosed?

Diagnosing tarsal tunnel syndrome can be challenging because its symptoms often overlap with other causes of chronic heel pain. Burning pain beneath the heel may easily be mistaken for plantar fasciosis, while numbness and tingling may be attributed to diabetes, lumbar spine disorders or peripheral neuropathy. The diagnosis therefore depends on combining a careful clinical assessment with appropriate investigations rather than relying on a single test.

The assessment begins with a detailed history. Patients are asked where the pain is located, whether it burns, tingles or radiates into the arch or toes, how long the symptoms have been present and what activities make them worse. Symptoms that increase with prolonged standing, walking or exercise and improve with rest are commonly reported. A history of previous ankle injury, flat feet, diabetes or inflammatory arthritis may also provide valuable diagnostic clues.

Clinical examination is the most important part of the assessment. The clinician evaluates the exact distribution of the symptoms, foot posture, ankle movement, gait and any biomechanical abnormalities that may increase pressure within the tarsal tunnel. Particular attention is paid to identifying tenderness along the course of the posterior tibial nerve behind the medial malleolus, the bony prominence on the inside of the ankle.

One commonly used clinical test is Tinel's sign. This involves gently tapping over the posterior tibial nerve within the tarsal tunnel. Reproduction of tingling, burning or electric shock-like sensations radiating into the sole of the foot suggests irritation of the nerve. Although a positive Tinel's sign supports the diagnosis, it is not specific and cannot confirm tarsal tunnel syndrome on its own.

Muscle strength and sensation are also examined. The clinician assesses for reduced sensation on the sole of the foot, altered light touch, changes in two-point discrimination and weakness of the small intrinsic muscles supplied by the posterior tibial nerve. More advanced nerve compression may produce subtle muscle wasting, although this is relatively uncommon.

Diagnostic ultrasound has become an increasingly valuable investigation. Ultrasound allows real-time visualisation of the posterior tibial nerve and surrounding structures. It can identify ganglion cysts, enlarged veins, tendon sheath swelling, accessory muscles or other space-occupying lesions compressing the nerve. Dynamic ultrasound also enables the clinician to assess the nerve during movement and simultaneously evaluate the plantar fascia, helping determine whether more than one condition is contributing to the patient's heel pain.

MRI may be recommended when deeper structural abnormalities are suspected or when ultrasound findings are inconclusive. MRI provides excellent visualisation of the tarsal tunnel, surrounding tendons, ligaments, bone and soft tissues. It is particularly useful for identifying tumours, ganglion cysts, inflammatory conditions or previous injuries that may be responsible for nerve compression.

Nerve conduction studies and electromyography (EMG) are sometimes used to assess nerve function. These tests measure how well electrical signals travel along the posterior tibial nerve. Abnormal results may support the diagnosis of tarsal tunnel syndrome, particularly in more advanced cases. However, normal nerve conduction studies do not exclude the condition. Mild or intermittent nerve compression may produce normal test results despite clinically significant symptoms.

One of the most important aspects of diagnosis is excluding other conditions that can produce similar symptoms. Plantar fasciosis, Baxter's nerve entrapment, lumbar radiculopathy, diabetic peripheral neuropathy, heel fat pad syndrome and calcaneal bone marrow oedema may all mimic aspects of tarsal tunnel syndrome. Many patients have more than one diagnosis simultaneously, making a systematic assessment essential.

Ultimately, no single investigation confirms tarsal tunnel syndrome. The diagnosis is based on the combination of the patient's history, physical examination and imaging findings. Establishing an accurate diagnosis allows treatment to focus on relieving pressure around the nerve while addressing the underlying cause of the compression.