What Is the Sinus Tarsi — and Why Its Syndrome Is Underdiagnosed

The sinus tarsi is a lateral foot space between the talus (ankle bone) and calcaneus (heel bone) — a tunnel-like gap containing the interosseous talocalcaneal ligament, cervical ligament, fat pad, and nerve endings that contribute to subtalar joint (the joint beneath the ankle) proprioception. Sinus tarsi syndrome occurs when these structures are disrupted — most commonly from a lateral ankle sprain that tears the interosseous ligament within the sinus tarsi — producing chronic lateral foot pain, subtalar instability, and a sensation of the hindfoot “giving way” that persists long after the ankle ligaments have healed. The syndrome is underdiagnosed because standard ankle sprain evaluation focuses on the lateral ankle ligaments (ATFL, CFL, PTFL) — the sinus tarsi space is not routinely palpated, and standard ankle X-rays do not show soft tissue disruption within the sinus tarsi. At Balance Foot & Ankle in Howell and Bloomfield Hills, Michigan, Dr. Tom Biernacki, DPM identifies sinus tarsi syndrome as a cause of persistent post-sprain lateral foot pain. Call (810) 206-1402.

Diagnosis — Palpation, Subtalar Stress Test, and MRI

The clinical diagnosis of sinus tarsi syndrome uses targeted examination: sinus tarsi palpation — direct tenderness at the sinus tarsi opening (located just anterior to the lateral malleolus, between the fibula and the lateral talar neck) — positive in over 90% of sinus tarsi syndrome cases; subtalar inversion stress test — passive inversion of the hindfoot with the ankle stabilized — reproduces pain and instability at the sinus tarsi; and the subtalar tilt test — assessing the degree of subtalar inversion/eversion compared to the uninjured side. MRI is the gold standard: demonstrates disruption, scarring, or synovitis within the sinus tarsi fat pad and interosseous ligament. Sinus tarsi syndrome often coexists with lateral ankle ligament laxity — both contribute to the “chronic ankle instability” presentation that is common in patients with repeated ankle sprains.

Conservative Management — Subtalar Stabilization

Sinus tarsi syndrome management differs from lateral ankle ligament rehabilitation because the unstable joint is the subtalar, not the talocrural (true ankle) joint: custom orthotics with lateral hindfoot posting (lateral wedge or varus posting of the heel) — counteracts the subtalar valgus drift that stresses the sinus tarsi; a high-quality lace-up ankle brace worn during all weight-bearing activity stabilizes both the ankle and subtalar joints; targeted subtalar proprioception rehabilitation — single-leg balance, BOSU ball training, and lateral peroneal strengthening (distinct from basic ankle proprioception exercises); and corticosteroid injection into the sinus tarsi space — 70% of patients experience 6+ months of significant pain reduction with a single injection, providing sufficient pain reduction for rehabilitation to be effective. Conservative management succeeds in approximately 60–70% of sinus tarsi syndrome cases.

Surgical Management — Sinus Tarsi Arthroscopic Debridement

For sinus tarsi syndrome that fails 4–6 months of conservative management, subtalar arthroscopy provides direct visualization and debridement of the sinus tarsi — removing the inflamed fibrofatty tissue, scarring, and synovitis that maintain chronic pain. Subtalar arthroscopy is a minimally invasive procedure performed through 2–3 small portals, with return to full activity in 6–8 weeks. Outcomes: 80–90% significant pain reduction at 1 year. For patients with concurrent subtalar instability (excessive subtalar tilt on stress imaging), subtalar ligament reconstruction may be performed simultaneously. Sinus tarsi syndrome combined with chronic lateral ankle ligament instability — the Brostrom-Gould lateral ankle reconstruction is performed concurrently with sinus tarsi debridement in these patients.

Sinus Tarsi Syndrome Treatment in Howell & Bloomfield Hills Michigan

Dr. Tom Biernacki, DPM evaluates persistent lateral ankle and hindfoot pain after ankle sprains with targeted sinus tarsi palpation, subtalar stress testing, and MRI coordination; provides custom orthotics with subtalar stabilization, sinus tarsi injection, and proprioception rehabilitation at Balance Foot & Ankle. Any patient with “ankle instability” that hasn’t responded to standard lateral ankle rehabilitation should have sinus tarsi evaluation. Serving Howell, Brighton, Milford, Bloomfield Hills, and all Southeast Michigan. Book your evaluation or call (810) 206-1402.

Your Board-Certified Podiatrists

Dr. Tom Biernacki, DPM

Board-Certified · FACFAS

Dr. Carl Jay, DPM

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Dr. Daria Gutkin, DPM

Podiatrist

Dr. Tom Biernacki, DPM

Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.