Sinus Tarsi Syndrome (STS)

The sinus tarsi is a tube or tunnel between the talus and the calcaneus bones. Sinus tarsi syndrome is pain or injury to this area. Traumatic injury to the ankle/foot (such as an ankle sprain) or overuse (such as repetitive standing or walking) are the main causes of this syndrome. Sinus tarsi syndrome is believed to occur following a single traumatic event or a series of ankle sprains that result in significant injuries to the talocrural interosseous and cervical ligaments. These injuries cause instability of the subtalar joint resulting in excessive supination and pronation movements.

Sinus tarsi syndrome (STS) is a clinical entity characterized by persistent anterolateral ankle pain secondary to traumatic injuries to the ankle. Historically, the etiology of this condition has not been well understood. Recent discussions of STS now describe this entity as primarily an instability of the subtalar joint due to ligamentous injuries that results in a synovitis and infiltration of fibrotic tissue into the sinus tarsi space.^2,3

Other Names

• Sinus Tarsi Syndrome (STS)
• Canalis Tarsi Syndrome
• First described by Denis O’Connor in 1958
• Most patients present in the 3rd, 4th decade of life (need citation)

ANATOMICAL AND KINESIOLOGICAL CONSIDERATIONS

The subtalar joint is comprised of the articulation of the talus and calcaneus across an anterior, middle, and posterior facet. These facets may have variations in their structure and alignments that will affect the movement and stability of the subtalar joint.⁴ Extrinsic and intrinsic ligaments provide static stability for the subtalar joint. Extrinsic ligaments include the calcaneofibular ligament and the deltoid ligament, which also provide stability for the talocrural joint. The talocalcaneal, interosseous, and cervical ligaments are the intrinsic ligaments that provide a strong connection for the calcaneal and talar joint surfaces.⁵ Ruptures of the intrinsic ligaments allow increased movement of the subtalar joint that may result in instability.^6–8

The motions of the subtalar joint and the entire rearfoot are complex and have been the subject of extensive study and controversy.^4,9,10 The osteokinematics of the subtalar joint occur about a triplanar axis to create pronation and supination movements.⁵ Supination motions of the subtalar joint create bony stability through the rearfoot and midfoot that is important for propulsive movements through the foot. Pronation motions create increased mobility of the rearfoot and midfoot joints allowing the foot to accommodate to uneven surfaces.^5,11 During running activities, athletes may weight bear entirely onto the forefoot, with ground reaction forces creating supination and pronation motions that occur from the midfoot into the rearfoot. Ground reaction forces during running create movements through the subtalar joint at a higher rate of acceleration and forces than during walking activities.¹²

The sinus tarsi space is filled with many connective tissues that contribute to the stability and the overall proprioception of the ankle. The space is filled with adipose tissue that serves as a bedding for numerous mechanoreceptors and free nerve endings, which along with the ligaments and muscles provide proprioceptive information on the movement of the foot and ankle.^2,13 The vascular supply of the sinus tarsi is provided by an anastomosis of the sinus tarsi and tarsal canal arteries.¹⁴ The extensor digitorum brevis muscle attaches to the medial and distal aspect of the sinus tarsi, running over the calcaneocuboid joint towards the toes. The inferior extensor retinaculum lies over the lateral aspect of this space and serves as a covering over the sinus tarsi.²

Pathophysiology

• General
  • Overall poorly understood condition and no widely accepted diagnostic criteria
  • Described as clinical entity characterized by persistent anterolateral ankle pain secondary to traumatic injuries to the ankle
  • Due to instability of the subtalar joint due to ligamentous injuries resulting in synovitis, infiltration of fibrotic tissue into the sinus tarsi space
• Controversy
  • Although generally accepted as a syndrome, some physicians argue that each case of STS can be attributed to a more specific diagnosis
  • For example, Frey et al. performed subtalar arthroscopy on 14 patients with STS, all of whom were given a more specific diagnosis such as a ligament tear post-operatively
• Canalis tarsi syndrome
  • A severe variant which can include medial hindfoot pain in addition to the typical lateral symptoms

Causes

• General
  • Caused by hemorrhage and/or inflammation of the synovial recesses of the sinus tarsi
  • With or without tears of the associated ligaments
  • This leads to synovitis, inflammation, infiltration of fibrotic tissues
• Causes
  • Trauma is the most common cause following a single or a series of ankle sprains^[rx]
  • Inflammatory arthritis such as rheumatoid arthritis, gout, or ankylosing arthritis.
  • Flatfoot deformity, tumors, and soft tissue impingement have also been implicated

Associated Conditions

• Lateral Ankle Sprain, Medial Ankle Sprain
• Sinus Tarsi
  • Cylindrical canal located in the hindfoot
  • Bordered by the neck of the talus and anterosuperior calcaneus

• Sports
  • Dancers
  • Volleyball
  • Basketball players
• Systemic
  • Overweight individuals
• Structural
  • Pes Planus
  • Hyper pronation deformities

Differential Diagnosis

• Fractures & Dislocations
  • Distal Tibia Fracture
  • Distal Fibular Fracture
  • Talus Fracture
  • Calcaneus Fracture
  • Subtalar Dislocation
  • Ankle Fracture (& Dislocation)
  • Peroneal Subluxation
• Muscle and Tendon Injuries
  • Peroneal Tendon Injuries
  • Achilles Tendonitis
  • Achilles Tendon Rupture
  • Posterior Tibial Tendon Dysfunction
  • Flexor Hallucis Longus Tendinopathy
• Ligament Injuries
  • Lateral Ankle Sprain
  • Medial Ankle Sprain
  • Syndesmotic Sprain
  • Chronic Ankle Instability
  • Intersection Syndrome Foot
• Bursopathies
  • Retrocalcaneal Bursitis
• Nerve Injuries
  • Peroneal Nerve Injury
  • Tarsal Tunnel Syndrome
• Arthropathies
  • Osteoarthritis of the Ankle
  • Osteochondral Defect Talus
• Pediatrics
  • Fifth Metatarsal Apophysitis (Iselin’s Disease)
  • Calcaneal Apophysitis (Sever’s Disease)
• Other
  • Haglunds Deformity
  • Posterior Ankle Impingement Syndrome
  • Sinus Tarsi Syndrome

Diagnosis

• History
  • Pain localized to the lateral hindfoot (sinus tarsi region)
  • Worse with walking, supination, adduction
  • The sensation of instability when walking, especially on uneven surfaces^[5]
• Physical Exam: Physical Exam Ankle
  • Inspect for Pes Planus
  • Tenderness over the lateral opening of the tarsal sinus
• Special Tests

Radiographs

• Standard Radiographs Ankle
• Findings
  • Osteoarthritis of the subtalar joint
  • Intraosseous cysts

CT

• Findings
  • Secondary bony changes (earlier than XR)

MRI

• Imaging modality of choice
  • Lektrakul found high sensitivity with unknown specificity^[6]
• Challenges
  • Oblique course of ligamentous structures in the sinus tarsi makes identifying a specific diagnosis difficult
  • Lee et al: found low agreement between symptomatic MRI and arthroscopy^[7]
• Findings
  • Inflammation
  • Scar tissue formation
  • Ligamentous injuries
• Ganglion cysts in the region of the sinus tarsi may compress the posterior tibial nerve.

Management

Nonoperative

• NSAIDS
• Orthotics/ Inserts
  • Stable shoes
  • Ankle Sleeve
  • Other orthotic
• Immobilization
• Cryotherapy

Operative

• Indications
  • Presence of ganglion cyst
• Technique
  • Synovectomy
  • Debridement