Tarsal Tunnel Syndrome - A Comprehensive Review

Abstract

Tarsal tunnel syndrome (TTS) refers to compression of the posterior tibial nerve as it traverses the tarsal tunnel in the ankle. First described by Keck and Lam in 1962, TTS is an underdiagnosed cause of heel pain and foot dysfunction.^1,2 The tarsal tunnel contains the tibial nerve, posterior tibial artery, and tendons of the tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles. Compression of the tibial nerve within this tunnel leads to pain, numbness, tingling, and weakness along its distribution.

The clinical presentation of TTS can vary due to the numerous etiologies and range of structures involved. Symptoms may develop insidiously over months to years or have a traumatic onset. Lack of definitive clinical tests or imaging often delays diagnosis, which contributes to poor patient outcomes and treatment success. In severe or long-standing cases, permanent nerve damage may occur if left untreated.

TTS deserves increased recognition given its potential to significantly impact mobility and quality of life. This review provides a comprehensive overview of the anatomy, etiology, diagnosis, and management of TTS. Optimal strategies to diagnose and treat this condition based on available evidence are discussed to improve patient outcomes and limit disability. Early diagnosis and intervention are key to avoiding permanent nerve injury and maximizing the benefits of treatment, whether conservative or surgical.

Anatomy

The tarsal tunnel is a firm osteofibrous canal in the ankle formed by the flexor retinaculum and talus, navicular, and calcaneus bones. The flexor retinaculum spans between the medial malleolus and the calcaneus, forming the roof of the tunnel. It contains tendons of the tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles, as well as the posterior tibial artery, vein, and nerve.¹

The tibial nerve originates from the sciatic nerve in the popliteal fossa. It descends deep into the calf, providing motor branches to the soleus, tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles. Near the ankle, the tibial nerve bifurcates into the medial and lateral plantar nerves, which provide sensory innervation to the plantar surface of the foot and toes.² These nerves and their branches are susceptible to compression within the tarsal tunnel.

The medial plantar nerve provides sensory branches to the medial arch, the plantar aspect of the first through third toes, and the medial two lumbricals. The lateral plantar nerve supplies the lateral arch, the plantar aspect of the fourth and fifth toes, all interossei, and the remaining lumbricals. Terminal branches of these nerves form the common plantar digital nerves, which supply sensory innervation between the toes.³

Vascular supply to the tarsal tunnel contents arises from branches of the posterior tibial artery. It provides the medial and lateral plantar arteries at the bifurcation of the tibial nerve, as well as branches that vascularize the flexor retinaculum, nerve, and tendons within the tunnel.⁴ Impaired blood flow contributes to nerve compression and dysfunction in TTS.

In summary, the tibial nerve and its branches, along with the posterior tibial artery and tendons within the tarsal tunnel, are at risk of compression due to changes in tunnel size, volume, or dynamics. A detailed understanding of tarsal tunnel anatomy is essential to diagnosing and treating TTS. The next section will review the etiologies underlying nerve compression and the resulting clinical manifestations.

Etiology

The etiology of TTS includes a range of intrinsic and extrinsic factors that compress the tibial nerve within the tarsal tunnel. Intrinsic causes originate within the tunnel itself, such as varicosities of the posterior tibial vein or tenosynovitis of the tendons. Extrinsic causes exert pressure from outside the tunnel, including trauma, ankle instability, space-occupying lesions, systemic conditions, and idiopathic factors.⁵

Varicosities of the posterior tibial vein are found in 20% of patients with TTS.⁶ Valve insufficiency leads to venous dilation and congestion, which compresses the tibial nerve. Tenosynovitis refers to inflammation of the flexor tendon sheaths, which occupy a substantial portion of the tunnel and can distort its shape. Trauma such as fractures, sprains, or direct crush injuries fracture bones, rupture tendons, or damage nerves within the tarsal tunnel.

Ankle instability caused by conditions like posterior tibial tendon dysfunction alters the dynamics and loading through the tarsal tunnel. This leads to stretching or irritation of the tibial nerve with excessive motion. Space-occupying lesions include ganglia, neuromas, lipomas, or other masses that physically compress the tibial nerve.⁷ Systemic conditions associated with TTS include diabetes, hypothyroidism, rheumatoid arthritis, and obesity due to fluid retention or biochemical changes.⁸

In many cases, no underlying cause can be identified, which is referred to as idiopathic TTS. Contrary to common belief, a flat or pronated foot is not directly linked to the development of TTS.⁹ However, foot deformities may contribute to altered gait, biomechanics, and load transmission through the ankle, which could predispose to this condition through other mechanisms.

Clinical Manifestations

The clinical presentation of TTS varies depending on the underlying etiology and severity of tibial nerve compression. Symptoms include pain, numbness, tingling, weakness, and a sensation of walking on pebbles or sand. Pain is typically worse at night and with activity, located in the sole of the foot and radiating to the toes.¹⁰ Paresthesias tend to follow the distribution of the medial and lateral plantar nerves. Weakness is usually secondary to intrinsic muscle atrophy, leading to clawing of toes and loss of arch.¹¹

Patients frequently report a gradual onset of symptoms that have persisted for months or years. However, traumatic TTS presents more acutely in association with an inciting event. Pain is often described as aching, burning, or stabbing in nature. Numbness and tingling are initially intermittent but become constant in severe, longstanding cases as nerves degenerate. Motor deficits occur late, and their presence indicates advanced disease.

On a physical exam, Tinel’s sign over the tarsal tunnel elicits pain and paresthesia into the plantar foot, which is considered a positive finding. Swelling or a palpable mass may be noted within the tunnel. The flexor retinaculum and tendons feel tense or thickened. Atrophy of intrinsic foot musculature results in claw toe deformities, a loss of arch, and a “bag of worms” feel upon plantar palpation.⁹ Pain and paresthesia can be elicited through passive stretch and resistance testing of toe flexors and abductors. A vascular exam reveals decreased or absent pedal pulses in severe cases. Neurological testing confirms decreased sensation to light touch, pinprick, temperature, and vibration modalities.

Diagnosis remains challenging without definitive clinical tests and is made through a combination of symptoms, physical findings, and ruling out other potential causes of heel pain or nerve compression. A diagnostic workup may include imaging, nerve conduction studies, and diagnostic injections, which are useful to support a diagnosis of TTS when findings are inconclusive.

Diagnostic Modalities

Diagnosing TTS begins with a thorough history and physical exam to determine symptoms, identify potential etiological factors, and rule out other causes of heel pain or nerve compression. Diagnostic studies provide objective evidence to support a clinical diagnosis of TTS when findings are inconclusive.

These include:

Imaging: Radiographs evaluate the bony anatomy and alignment of the ankle and hindfoot. Ultrasound allows dynamic visualization of the tibial nerve, flexor tendons, and other structures within the tarsal tunnel. MRI defines soft tissue morphology and can detect space-occupying lesions, tendonitis, or a Baker’s cyst.¹² These modalities exclude other pathologies but have limited sensitivity and specificity for TTS.

Nerve conduction studies: Electromyography (EMG) assesses the integrity and conduction velocity of the tibial nerve and its branches. A reduced amplitude of sensory responses in the medial and lateral plantar nerves or delayed distal motor latency of the abductor hallucis muscle suggest chronic nerve compression.¹³ However, findings are often normal, especially in mild cases or when symptoms have a gradual onset over years. Serial studies may be required to detect abnormalities.

Diagnostic injections: A local anesthetic injection into the tarsal tunnel provides temporary relief of symptoms, which helps confirm the diagnosis. Cortisone reduces local inflammation that may be contributing to nerve compression, with longer-term relief indicating a role in symptoms. These injections also help determine if surgical intervention may be beneficial when symptoms return after the injected drugs lose effect.¹⁴

Pressure provocation tests: The pressure probe and Fowler’s test manually apply focal pressure over the tarsal tunnel to reproduce patient symptoms.¹⁵ These in-office tests lack standardization, sensitivity, and specificity, but their use is described for diagnosis when supported by clinical findings.

No single diagnostic modality can confirm or exclude TTS. Diagnosis relies on clinical presentation supported by findings across imaging, electrophysiology, and diagnostic injections. When uncertain, a trial of conservative treatment may also be useful to determine the potential benefit of surgical management.

Differential Diagnosis

Conditions that cause heel pain or nerve compression and mimic the symptoms of TTS include:

Plantar fasciitis: Dull ache in the sole, heel, and arch, worse in the morning or with initial steps. Tenderness at the medial calcaneal tubercle. 50% of patients have flat feet or high arches.¹⁶ X-rays are normal; US or MRI may show plantar fascia thickening. Symptoms improve with stretching, orthotics, or steroid injections.

Stress or bony fractures: localized tenderness over the fracture site. History of increased activity or trauma. Radiographs detect fractures, and MRI is confirmative. Immobilization and avoiding weight-bearing relieve symptoms.

Morton’s neuroma: sharp pain and paresthesias in the 3rd web space, worse with walking, jumping, or toe squeeze. Palpable mass between metatarsals on exam. Diagnosis is clinical; US, MRI, or diagnostic injections may be used. Conservative treatment focuses on shoe modifications, orthotics, and steroid injections.

Nerve entrapment: Compression at a single site elicits symptoms. Common locations include the medial malleolus (Baxter’s nerve), the deep peroneal nerve at the foot dorsum, or the intermetatarsal nerves at the toes. The diagnosis is clinical; electrophysiology studies confirm nerve dysfunction. Treatment focuses on padding, orthotics, steroid injections, or surgery to release the entrapped nerve.

Vascular claudication: Aching pain in the arch, heel, or calf muscles with walking that subsides with rest. Absent or diminished pedal pulses on examination The anklebrachial index detects arterial insufficiency. Treatment includes lifestyle changes, medication, and, in severe cases, surgical revascularization.

The diagnosis of TTS requires a thorough clinical workup to rule out conditions that could mimic or contribute to symptoms. The distribution of pain and paresthesias, findings on imaging, and response to diagnostic injections help distinguish TTS as the primary diagnosis and underlying cause of disability. The key to differentiation is identifying or excluding pathologies at sites other than the tarsal tunnel that may be contributing to or primarily responsible for the patient’s symptoms.

Management

Treatment of TTS aims to reduce tibial nerve compression through conservative or surgical means, depending on symptom severity and the underlying etiology. Conservative options are trialed first, with surgery reserved for those failing medical management or with acute trauma, space-occupying lesions, or fixed deformities.

Conservative treatment includes:

Rest and immobilization: Reduces mechanical compression from activity. Especially beneficial in traumatic or acute cases. Prescribe limited weight-bearing and ankle bracing for up to 6 weeks.¹⁷

Physical therapy: Focuses on stretching and strengthening intrinsic foot and ankle muscles. Ultrasound, massage, and iontophoresis with dexamethasone provide anti-inflammatory effects.¹⁸ In a study of 46 TTS patients, PT reduced symptoms in 70% of cases, with benefits maintained at 6 months.¹⁹

Orthotics and bracing: Arch support, padded shoe inserts, and ankle braces or strapping redistribute pressure and provide stability. Benefits over 75% of patients in studies with significant pain and function improvement.^20,21

Medications: NSAIDs reduce inflammation and pain. Gabapentin, or pregabalin, for neuropathic pain has some benefits. Steroid injections may be useful when symptoms are refractory to other treatments.²² Injections of hydrocortisone showed over 90% efficacy in multiple studies.^23,24

Activity modification: Avoid walking long distances, climbing stairs or hills, driving, and prolonged standing or sitting. Lifestyle changes are very effective at controlling symptoms in mild to moderate cases.²⁵

For severe or refractory cases, surgery aims to release the flexor retinaculum and decompression the tibial nerve. Open procedures were first described in 1962 and popularized in the 1970s. Recent minimally invasive options include endoscopic and percutaneous techniques with similar efficacy but lower morbidity:²⁶

Open decompression: Gold standard, with up to 90% success rate. Requires a 3-5 cm incision along the posteromedial ankle.²⁷ Risks include damage to vascular and tendon structures, as well as wound complications.

Endoscopic decompression: Two small incisions through which surgical instruments are inserted. Magnification and illumination allow clear visualization of the tibial nerve. Similar patient outcomes to open surgery with a lower risk of complications.²⁸

Percutaneous decompression: Needle is inserted under US guidance to cut the flexor retinaculum. Least invasive option but technically difficult, and the risk of neurovascular damage is higher. There is limited available evidence on efficacy.²⁹

In summary, a graduated approach, starting with conservative modalities followed by surgical options if needed, provides the best opportunity for symptom relief and functional restoration in patients with TTS. Monitoring response to treatment guides escalation to more aggressive interventions to gain control of symptoms and avoid long-term disability from this condition.

Conclusion

Tarsal tunnel syndrome requires a multidisciplinary approach for diagnosis and management due to its complex anatomy and variable etiology. Conservative treatment provides relief for most patients, but minimally invasive surgery may be required for refractory or severe diseases. Close follow-up and patient education are essential to maximizing and maintaining improvements from interventions. No single diagnostic test can conclusively diagnose TTS, so a high level of clinical suspicion and a combination of modalities to rule out other causes are needed. With a focused treatment plan addressing all underlying factors, a significant reduction or resolution of pain, paresthesia, and weakness can be achieved, allowing a return to high-level function.