[Overview] A series of symptoms arising from lesions within the tarsal sinus and its adjacent structures is called tarsal sinus syndrome. Etiology and pathology】 Injury to the intertrochanteric and anterior ligaments and other structures of the talar heel following an ankle inversion sprain is probably the most common cause of tarsal sinus syndrome. Injury to the subtalar joint may also lead to the development of tarsal sinus syndrome. Other causes are (1) abnormal foot structure, such as flat feet, high arched feet, forefoot valgus, and tarsal junction; (2) systemic systemic pathologies, such as seronegative and positive spondylitis; (3) infections; (4) lipomas and cysts in the tarsal sinus; and (5) prolonged plaster immobilization of the foot in the valgus and adductor position, which causes contracture and scar formation in the tarsal sinus surrounding tissues, leading to tarsal sinus syndrome of medical origin. Chronic synovitis is its most common pathological manifestation. Pain in the tarsal sinus area may be due to injury to the ligaments and instability of the subtalar joint, as well as slow blood flow to the tissues due to local inflammation following trauma, producing intra-sinus hypertension. The injury of the neurovascular in the tarsal sinus also causes the proprioceptive injury of the ligament and aggravates the instability of the subtalar joint. 【Clinical manifestations】 History: Internal rotation sprain of the ankle joint. Symptoms: pain in the ankle joint or tarsal sinus area. Some patients may have a feeling of instability in the ankle joint and weakness in walking. Sometimes the pain radiates to the lateral side of the foot. Some patients may have abnormal sensations such as heat, coldness, numbness and pain in the lower leg. The pain is aggravated when walking and foot inversion. On examination: the patient is allowed to extend the foot slightly dorsally, and pressure on the tarsal sinus triangle triggers pain, sometimes local swelling is seen, and normal movement of the ankle and subtalar joint is observed. Taillard et al. described four clinical manifestations of tarsal sinus syndrome: (1) direct pressure pain in the tarsal sinus area, especially when the patient is allowed to stand on uneven ground or after internal rotation of the subtalar joint; (2) joint instability on uneven ground; (3) pain relief after local closure of the tarsal sinus; and (4) clinical and radiographic examinations that do not confirm subtalar joint instability. Imaging examinations: X-rays are often normal. MRI may be helpful in detecting lesions within the tarsal sinus. MRI may show abnormalities such as ① low signal on T1 and T2 images, which may be a fibrotic lesion; ② low signal on T1 and high signal on T2, indicating possible synovial inflammation or non-specific inflammatory changes; ③ multiple fluid accumulations within the tarsal sinus, which may be a synovial cystic lesion. 【Treatment】 Non-surgical treatment: Most patients can recover normal function after 4-8 weeks. Physiotherapy, non-steroidal anti-inflammatory and analgesic drugs, and tarsal sinus closure treatment. Exercise of peroneal tendon and proprioceptive training for patients with unstable sensation. Braking, such as immobilization with tape or a brace, to limit the movement of the subtalar joint. Surgical treatment: Surgery is recommended for patients who cannot be relieved by non-surgical treatment. The goal of surgery is decompression of the tarsal sinus. Surgery can be done either incisionally or arthroscopically. Incisional surgery involves severing the beginning of the bunion and toe extensor muscles and removing or releasing the fat, fascia and bursa within the tarsal sinus. Complete removal of the tarsal sinus contents results in postoperative wound invagination and sometimes blood accumulation in the sinus, making the incision difficult to heal. Regardless of whether the surgery is incisional or microscopic, the surgery should be performed by: (1) probing the talocrural joint surface for osteochondral damage; (2) removing the joint free body; (3) removing the intra-articular adhesions; (4) removing the inflamed and hyperplastic synovial membrane; (5) removing the torn or extruded soft tissue; and (6) evaluating the stability of the talocrural joint. If there is significant degeneration of the subtalar joint, subtalar fusion may be required. Postoperative complications include peroneal nerve injury, incisional infection, and sinus tract formation.