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Diagnostic Features
Tarsal Tunnel Syndrome
Introduction
Tarsal Tunnel Syndrome (TTS) is a peripheral neuropathy involving the posterior tibial nerve or its branches within the tarsal tunnel. The tarsal tunnel is a fibro-osseous space formed by the flexor retinaculum, a thick band of tissue that runs along the inside of the ankle, and the underlying bony structures (talus, calcaneus, and medial malleolus). The posterior tibial nerve, artery, and tendons pass through this tunnel.
TTS may arise as a result of poor biomechanics, trauma, local space-occupying lesions, or systemic diseases. It is considered an uncommon condition leading clinicians to misdiagnose it as Plantar Fasciitis. TTS is equivalent to Carpal Tunnel Syndrome in the wrist.
The following structures pass through the tarsal tunnel:
- Tibialis posterior tendon
- Flexor digitorum longus tendon
- Flexor hallucis longus tendon
- Posterior tibial artery and vein
- Posterior tibial nerve (L4-S3)
Several risk factors have been identified for the onset of TTS. These include:
- Previous trauma (particularly with calcaneal fracture)
- Presence of pes planus
- Prolonged weight bearing
- Rheumatoid arthritis and other seronegative arthritides
- Obesity
- Fluid retention
- Space-occupying lesion (e.g., lipoma or ganglion)
History
- Pain in the medial ankle, heel, and foot, sometimes extending to the toes
- Pain quality is usually described as burning combined with tingling and/or numbness
- Cramping in the medial sole of the foot may occur
- Pain brought on and worsened by prolonged weight-bearing
- Gradual pain relief with rest
- Nocturnal pain may be present
Physical Examination
- Local tenderness directly over the tarsal tunnel
- Aggravation of pain with passive ankle dorsiflexion and/or foot eversion
- Presence of Tinel’s Sign
- Positive Dorsiflexion-Eversion test
- Positive Triple Compression Stress test
- Variable sensory loss often involving the medial sole of the foot
- Atrophy of intrinsic foot musculature when the nerve injury is severe
Imaging
Plain radiography may be helpful to identify any structural abnormalities including the presence of osteophytes, tarsal coalition, or evidence of previous trauma. Ultrasound or MRI is useful for evaluating soft tissue abnormalities including tendonitis, tenosynovitis, lipomas, and ganglion cysts. Nerve conduction studies may be used to reveal abnormalities in the function of the posterior tibial nerve including slowing of conduction velocities.
Red Flags
The following are examples of red flags for patients presenting with foot pain:
- History of a significant injury
- Severe pain
- Unrelenting pain
- Nocturnal pain or pain at rest
- Fever
- Deformity
- Large joint swelling
- Significant loss of range of motion
- Significant neurological impairment
- Severe tenderness on palpation or severe pain with any examination procedure
If any red flags are identified during history taking and clinical examination, referral for urgent medical evaluation and further investigation is warranted.
Clinical Tips
Differential Diagnosis
In the adult age group, in addition to Tarsal Tunnel Syndrome, the differential diagnosis of medial foot pain should include other conditions such as:
- Plantar Fasciitis
- Myofascial Pain Syndromes of the abductor hallucis and gastrocnemius muscles
- Abductor hallucis strain
- Tibialis posterior tendinopathy
Plantar Fasciitis Vs Tarsal Tunnel Syndrome
In plantar fasciitis, pain is experienced in the plantar heel with the first step in the morning or when arising during the day from a resting position. The pain eases quickly after a few steps and does not recur with continued walking. The physical finding is discrete tenderness over the medial calcaneal tubercle.
Tarsal tunnel syndrome has a much broader area of pain, extending from the medial heel along the sole and as far as the toes. It usually begins with prolonged walking and becomes worse the longer the person walks. Unlike plantar fasciitis, the pain does not remit immediately with rest but eases gradually after non-weight bearing. The symptoms are typically neurogenic, with paresthesias and possibly night pain.
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