Sinus tarsi syndrome is a frequently overlooked cause of lateral ankle and hindfoot pain — most commonly developing after an ankle sprain that “never quite healed.” The sinus tarsi is a small tunnel located between the talus and calcaneus on the lateral side of the ankle, housing the interosseous talocalcaneal ligament (ITCL), fat tissue, nerve endings, and small blood vessels. When this structure is damaged or inflamed, it produces a characteristic lateral hindfoot pain pattern that can be mistaken for recurrent ankle sprain, subtalar arthritis, or peroneal tendon pathology.

Anatomy and Mechanism

The sinus tarsi — literally “tunnel of the foot” — sits just anterolateral to the subtalar joint. The ITCL is the primary stabilizing structure within the tunnel. Inversion ankle sprains can damage not only the lateral ankle ligaments (ATFL, CFL) but also stretch or tear the ITCL and surrounding soft tissues in the sinus tarsi. Inflammation, scar tissue formation, and fibrosis within the tunnel produce the chronic pain syndrome.

Sinus tarsi syndrome is responsible for approximately 70% of persistent lateral ankle pain following inversion sprains that has not resolved with standard rehabilitation. It is underdiagnosed because the sinus tarsi is not well-visualized on standard ankle X-rays and requires MRI for definitive assessment.

Clinical Presentation

Characteristic features: lateral hindfoot pain at the entrance of the sinus tarsi (just anterior and inferior to the lateral malleolus, anterior to the peroneal tendons), localized tenderness with direct pressure on the sinus tarsi, pain with hindfoot inversion and eversion, a feeling of instability on uneven ground, and pain with prolonged weight bearing that improves with rest. Swelling is typically mild or absent.

Diagnosis

Clinical diagnosis is based on the history of ankle sprain, characteristic location of tenderness over the sinus tarsi, and symptom reproduction with subtalar stress testing. A diagnostic injection of local anesthetic into the sinus tarsi that relieves pain is both diagnostic and therapeutic — immediate pain relief from injection strongly confirms the diagnosis.

MRI demonstrates inflammation, scar tissue, or ITCL pathology within the sinus tarsi — useful for planning treatment and ruling out associated pathology (osteochondral lesions, peroneal tendon tears).

Treatment

Conservative management is successful in approximately 70% of cases:

• Cortisone injection into the sinus tarsi: Both diagnostic and therapeutic. Many patients achieve long-term relief with one or two injections combined with physical therapy.
• Custom orthotics: Controlling excessive subtalar pronation reduces dynamic stress on the sinus tarsi. A custom orthotic with lateral heel wedge and arch support addresses the biomechanical driver.
• Physical therapy: Peroneal strengthening, proprioception training, and subtalar mobilization address the functional instability that perpetuates symptoms.
• Bracing: Ankle-foot orthosis or lace-up ankle brace during higher-risk activities.

For refractory cases failing 3–6 months of conservative management, arthroscopic sinus tarsi debridement removes scar tissue and provides excellent outcomes — typically 80–90% good to excellent results. Subtalar arthroscopy allows simultaneous treatment of associated subtalar pathology.

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.