Sinus tarsi syndrome

Sinus tarsi syndrome (STS) is the clinical syndrome of pain and tenderness of the lateral side of the hindfoot, between the ankle and the heel. Imaging often demonstrates the ligaments and soft tissues in the sinus tarsi are injured.

Epidemiology

Sinus tarsi syndrome has been described in dancers, volleyball and basketball players, overweight individuals, and patients with flatfoot and hyperpronation deformities. The incidence of sinus tarsi syndrome is unknown, but it has been associated with ankle sprains that may also result in talocrural joint instability. Most patients present in the 3^rd to 4^th decades of life.

Clinical presentation

• localised pain in the sinus tarsi region: worsens when firm pressure is placed over the lateral opening of the tarsal sinus, and is most severe during walking or supination and adduction of the foot
• feeling of instability aggravated by weight bearing, especially on uneven surfaces
• pain on palpation of the sinus tarsi with aggravation on foot inversion and eversion
• cessation of pain on injection of a local anaesthetic into the sinus tarsi is diagnostic for sinus tarsi syndrome

Pathology

Aetiology

Sinus tarsi syndrome probably occurs following one single or a series of ankle sprains that also result in significant injuries to the talocrural interosseous and cervical ligaments. This causes instability of the subtalar joint in supination and pronation movements. In summary, sinus tarsi syndrome can be primarily described as an instability of the subtalar joint due to ligamentous injuries that result in synovitis and scar tissue formation in the sinus tarsi. Haemorrhage or inflammation of the synovial recesses of the sinus tarsi can also cause scarring without tears of the associated ligaments.

Associations

• gout ⁶

Radiographic features

Plain radiograph

Osteoarthritis of the subtalar joint and intraosseous cysts may be present in advanced cases.

CT

Can shows secondary bony changes at an earlier stage than radiography.

Bone scan/scintigraphy

Inflammatory changes may be attributed to the sinus tarsi/subtalar region.

MRI

MRI is probably the best test to show changes in the soft tissues of the sinus tarsi including inflammation, scar tissue formation or ligamentous injuries. The T1-hyperintense fat in the sinus tarsi space is replaced by either fluid or scar tissue, and the ligaments may be disrupted. Ganglion cysts in the region of the sinus tarsi may compress the posterior tibial nerve.

Treatment and prognosis

Conservative treatment is usually effective. It may include anti-inflammatory drugs, stable shoes, a period of immobilisation, cryotherapy, ankle sleeve and orthoses. Treatment of ganglion cysts in the sinus tarsi typically consists of surgical excision. Recommendations for rehabilitation include balance and proprioceptive training, and muscle strengthening exercises.

History and etymology

It was first described by Denis O'Connor in 1958.

Differential diagnosis

For the clinical presentation of sinus tarsi syndrome, consider:

• cuboid subluxation
• peroneal tendon disorders