Tarsal tunnel syndrome: symptoms and treatment

BOFAS, the British Orthopaedic Foot and Ankle Society, describes it as a set of symptoms caused by entrapment of the posterior tibial nerve, or its branches, within the tarsal tunnel. It says the condition is analogous to carpal tunnel syndrome in the hand but much less common, and is an important possibility to consider in heel pain.

The tarsal tunnel is a narrow space on the inside of the ankle beside the ankle bones. The Bexley musculoskeletal service describes it as a bundle of tendons, arteries and nerves held within a thick fibrous ligament. When there is not enough room, the nerve is squeezed or irritated.

Kent Community Health says pressure on the nerve causes pain, a burning sensation, tingling and sometimes numbness on the sole. Tapping the inside of the ankle can make symptoms spread into the arch or toes, called Tinel's sign, and moving the ankle up and down can aggravate them.

The Bexley service lists pain around the inside of the ankle sometimes extending into the arch, numbness and tingling on the inside of the ankle or sole, worsening pain with activity, and pain that lessens with rest and elevation. Burning or shooting pain, pins and needles are the "nerve symptoms" patients describe.

BOFAS notes that symptoms are often worse with exercise or tight footwear and can occur at night.

Kent Community Health says flat feet raise the risk, because the changed shape of the rear foot stretches and compresses the nerve. Inflammation on the inside of the ankle, from a previous injury or tendon overuse, can also be responsible, and occasionally a cyst or ganglion presses on the nerve.

The Bexley service adds excess body weight and a sudden increase in activity such as running. BOFAS separates causes into those inside the tunnel, such as bony spurs, tendon inflammation, ganglions and other space-occupying lesions, and those outside, including heel malalignment, leg swelling from heart failure or pregnancy, inflammatory arthritis, diabetes and poor circulation.

BOFAS says the mainstay of diagnosis is careful history and examination, looking for tenderness along the nerve and a positive Tinel's test. The Bexley service agrees that a thorough history and physical examination usually suffice.

Tests are used when there is doubt. BOFAS lists weight-bearing X-rays to look for malalignment, bony spurs, previous injury and tarsal coalitions, ultrasound to show ganglions, tendon inflammation or other pressure, MRI to show space-occupying lesions and the nerve's course, and nerve conduction studies. It adds that a normal nerve test does not rule the condition out because of false negatives.

Kent Community Health says a scan is not always needed, but if there is no improvement with reduced activity and an insole, ultrasound or MRI may be considered to look for a cyst, ganglion or another tendon provoking the problem.

Kent Community Health advises rest, or at least reduced activity, to let symptoms settle. If you want to keep walking, avoid hills and keep to flat ground. It suggests avoiding flat shoes and wearing a shoe with a heel of about 2 cm, which reduces nerve compression, and notes that pharmacy anti-inflammatory medication may help if the inside of the ankle is swollen.

The Bexley service describes relative rest, avoiding running and jumping while symptoms settle, with swimming and cycling usually tolerated, an ice pack for up to 20 minutes every 2 to 3 hours (not if you have cold sensitivity, an open wound, poor circulation or reduced sensation), supportive stable shoes, insoles that stop the foot rolling inwards, and calf stretching and nerve exercises. It also mentions bracing for flat feet or severe symptoms.

An insole to change the position of the rear foot can relieve pressure on the nerve, says Kent Community Health, and laser therapy may help if the nerve is correctly targeted. BOFAS says ultrasound-guided anaesthetic and steroid injections can help both to confirm the diagnosis and to treat. The Bexley service says steroid injections carry a risk to nearby tendons and are generally a last resort.

BOFAS says surgery may be considered if non-operative measures have been exhausted and symptoms persist. Decompression is most commonly done through an open incision over the flexor retinaculum, releasing the tight band and freeing the nerve, in a similar way to carpal tunnel release.

BOFAS reports that the best results are seen when the cause is a compressive lesion such as a ganglion cyst, and that surgical success rates vary widely, from 45% to 96%. It says outcomes tend to be better when surgery takes place within 12 months of symptoms starting.

The type of operation varies with symptoms and foot shape, according to the Bexley service, and is best discussed with a surgical professional. If an underlying inflammatory arthritis is found, BOFAS recommends referral to rheumatology.

BOFAS notes that tarsal tunnel syndrome is an important differential in heel pain, and that nerve tests can steer clinicians towards other causes such as peripheral neuropathy or a pinched nerve higher up the leg. Tendon problems on the inside of the ankle, plantar heel pain and diabetic nerve damage can share features.

Because treatment differs, an accurate diagnosis matters. If you have numbness in both feet, symptoms above the ankle, or diabetes, tell the clinician.

Many people are seen first by a GP, musculoskeletal service or podiatrist, who can start with footwear, insoles and exercise. Referral to a podiatric surgeon or orthopaedic foot and ankle service follows if scans or surgery are being considered.

A private foot and ankle specialist can arrange ultrasound, MRI and nerve tests, and offer injections or surgery. Since early treatment appears to give better results after surgery, a prompt assessment is reasonable if symptoms are persistent.