The sinus tarsi is a cone-shaped space between the neck of the talus superiorly and the anterior surface of the calcaneus inferiorly, opening laterally between the anterior process of the calcaneus and the lateral talar neck. It contains the interosseous talocalcaneal ligament, the cervical ligament, fat, synovial tissue, and the neurovascular supply to the sinus. The tarsal canal, the narrower medial continuation of the sinus tarsi, contains the sinus tarsi contents as they extend toward the medial ankle.
Sinus tarsi syndrome produces lateral hindfoot pain approximately 2 cm anterior and inferior to the lateral malleolus, classically following ankle sprains that stretch the sinus tarsi ligaments and cause synovitis within this space. Clinical diagnosis uses direct palpation of the sinus tarsi opening with reproduction of pain, and response to lidocaine injection into the sinus tarsi. MRI demonstrates signal changes within the sinus tarsi and ligament injury. Arthroscopic debridement of sinus tarsi synovitis through the anterolateral portal effectively treats refractory cases.
Post-sprain synovitis and fibrosis within the sinus tarsi produces persistent lateral hindfoot pain with a positive sinus tarsi point tenderness test and relief with sinus tarsi injection, managed with physiotherapy and injection, or arthroscopic debridement for refractory pain from fibrous obliteration of the sinus tarsi.
Fibrous or bony talocalcaneal coalition obliterates the normal sinus tarsi space on CT and MRI, preventing subtalar motion and producing a rigid flatfoot with peroneal muscle spasm in adolescents, managed by coalition resection or subtalar fusion depending on size and articular involvement.
