O’Connor first introduced tarsal sinus syndrome in 1957 as a condition that typically presents with chronic pain in the lateral ankle and tarsal sinus, mostly with a history of trauma. Anatomy The tarsal sinus is a conical cavity located between the neck of the talus and the anterosuperior aspect of the heel bone, which runs posteriorly and anteriorly. It is lined by a funnel-shaped tarsal sinus canal, which is immediately posterior to the talar process. The tarsal sinus is the division between the posterior talofibular joint and the anterior and middle joints. The main structures include the fat pad, small blood vessels, joint capsule, nerve endings, bursa, and ligaments (the medial, middle, and lateral roots of the intertrochanteric ligament, cervical ligament, and subextensor support band, see Figure 19-1-3 for details). Etiology 1. Trauma Approximately 70% of patients have a history of ankle trauma (entropion injury). The ligamentous structures in the tarsal sinus have a role in limiting excessive pronation of the subtalar joint. In a posterior foot rotation injury, the heel-fibular ligament ruptures first, followed by the cervical ligament and the heel talar interosseous ligament. Ligament rupture is the main cause of tarsal sinus syndrome. 2.Other About 30% of patients have no history of trauma, but are related to foot deformity, gouty arthritis or rheumatoid arthritis, etc. Injury pathology Tarsal sinus syndrome in the tarsal sinus may be caused by thickening of the synovial membrane in it, tendon sheath cysts, etc. In cases caused by trauma there is usually a partial tear of the intertarsal ligament, cervical ligament, etc. of the heel talus, which is also responsible for proprioceptive disturbances. In patients with rheumatoid arthritis, gout, and hyperpigmented villous nodular synovitis, the fat pad is commonly associated with synovial inflammation. Diagnosis and differential diagnosis 1. Symptoms Pain in the tarsal sinus region, aggravated by posterior rotation or inversion of the foot. Localized pain when walking, especially on uneven surfaces. Most patients have symptoms of tenderness, but no mechanical instability. 2. Signs (1) Sharp pressure pain in the tarsal sinus area. (2) Ankle passive inversion pain: pain in the tarsal sinus area when doing passive inversion or posterior rotation examination of the ankle joint. (3) Drawer test and inversion test: no ankle instability. 3. Auxiliary examinations include ankle X-ray, subtalar arthrography and MRI. (1) X-ray: including ankle anterior-posterior and lateral position, generally no abnormal findings. (2) Sub talocrural arthrography: the normal image of the lateral film is a slightly convex capsule in the anterior part of the sub talocrural joint with a small serration (normal crypt) at the front. If the normal crypt is absent, it is suggestive of tarsal sinus syndrome. (3) MRI: It can show partial rupture of the tarsal sinus ligament and soft tissue edema. It can also exclude osteochondral injuries of the ankle and talocrural joints, as well as old injuries of the lateral collateral ligament of the ankle. (4) Diagnostic closure: local injection of 2% lidocaine 2ml into the tarsal sinus, if the pain disappears, the diagnosis can be confirmed. 4. Differential diagnosis (1) Old injury of the lateral collateral ligament of the ankle joint: symptoms are mainly unstable, pressure pain point is at the anterior talofibular ligament or heel-fibular ligament, drawer test and inversion test find poor stability of the ankle joint, MRI can show old injury of the ligament. (2) Injury of the subtalar joint: X-ray or MRI shows signs of osteochondral injury of the subtalar joint. Treatment 1.Conservative treatment includes ultrasonic physiotherapy, hydrotherapy, oral NSAIDs and local closure. A mixture of 2% lidocaine 2ml and prednisone 1ml injected into the tarsal sinus is usually effective. 50-70% of patients with conservative treatment are effective. 2.Surgical treatment Surgical treatment can be performed when conservative treatment is ineffective. (1) Incision of the surgical lateral ankle Ollier incision, paying attention to the protection of the lateral dorsal cutaneous nerve of the foot, and removal of the fat pad of the tarsal sinus. If there is injury to the intertarsal ligament of the heel talus and it causes inflammation, the inflammatory tissue should be removed. (2) Arthroscopic surgery can be applied to remove the inflammatory tissue in the tarsal sinus, and at the same time, it can determine whether there is any damage to the ligament of the tarsal sinus, which is less invasive and has good clinical results.