The sinus tarsi is a small bony canal on the outer side of the hindfoot, located between the talus (ankle bone) and calcaneus (heel bone). It contains fat, ligaments, nerves, and blood vessels that contribute to subtalar joint stability and proprioception. Sinus tarsi syndrome is a clinical condition characterized by chronic lateral hindfoot pain, instability, and tenderness over this canal — most commonly following an ankle sprain that fails to fully resolve.
Sinus tarsi syndrome is closely related to ankle ligament injuries and is frequently an underrecognized consequence of inadequately treated sprains. It can also coexist with tarsal coalition, which similarly restricts subtalar motion and causes hindfoot pain, and must be distinguished from plantar fasciitis and calcaneal stress fracture in patients presenting with heel and hindfoot pain.
Causes
- Trauma and ankle sprains: The most common cause. Inversion ankle sprains damage the ligaments within the sinus tarsi, leading to scarring, synovitis, and chronic pain. Up to 70% of patients with sinus tarsi syndrome have a history of prior ankle sprain.
- Chronic ankle instability: Repeated sprains and residual ligament laxity allow abnormal subtalar motion, causing ongoing irritation of the sinus tarsi contents.
- Biomechanical factors: Flat feet (pes planus) increase subtalar pronation and load on the sinus tarsi; high arches (pes cavus) increase inversion stress. Either foot type can predispose to the condition.
- Tarsal coalition: Abnormal bony or fibrous connections between hindfoot bones — as seen in tarsal coalition — alter subtalar mechanics and can contribute to sinus tarsi irritation.
- Inflammatory arthritis: Conditions such as rheumatoid arthritis or synovitis can involve the subtalar joint and sinus tarsi directly.
- Overuse: Repetitive loading in runners and jumping athletes can cause cumulative stress to the ligaments and fat pad within the sinus tarsi.
- Poor footwear: Inadequate support accelerates abnormal hindfoot mechanics and increases ligament stress over time.
Symptoms
- Lateral hindfoot pain: The hallmark symptom — a persistent ache or sharp pain localized to the outer side of the ankle, just in front of and below the lateral malleolus, at the opening of the sinus tarsi canal.
- Point tenderness: Direct palpation over the sinus tarsi reproduces pain. This is a key diagnostic finding on physical examination.
- Instability: A subjective sensation of the ankle or hindfoot giving way, particularly on uneven ground or during direction changes.
- Swelling: Lateral ankle swelling, often subtle, that worsens with prolonged activity or weight-bearing.
- Pain with activity: Symptoms are consistently worsened by walking on uneven terrain, stairs, inversion movements, and sports activity.
- Pain at rest: In more advanced or inflamed cases, aching at rest or overnight may occur.
- Limited subtalar motion: Stiffness in the inward/outward rocking motion of the hindfoot (subtalar inversion/eversion) is commonly present.
Diagnosis
The sinus tarsi compression test is the key physical examination maneuver — firm pressure applied directly over the sinus tarsi while the ankle is inverted reproduces the patient's characteristic pain. Ankle stability is assessed with the anterior drawer and talar tilt tests to evaluate for concurrent lateral ligament laxity.
MRI is the preferred imaging study for sinus tarsi syndrome. The characteristic MRI finding is obliteration or replacement of the normal fat signal within the sinus tarsi by scar tissue, fibrosis, or synovitis — seen as loss of the bright T1 fat signal that is normally present in this space. MRI also identifies associated injuries including lateral ligament tears, talar dome osteochondral lesions, subtalar joint synovitis, and peroneal tendon pathology that may be contributing to symptoms. A diagnostic anesthetic injection into the sinus tarsi that provides temporary complete pain relief further confirms the diagnosis.
Treatments
Conservative treatment (first-line for most patients):
Rest and activity modification to reduce provocative loading, NSAIDs for pain and inflammation, and a structured physical therapy program targeting peroneal strengthening, proprioceptive retraining, and subtalar stabilization. Custom orthotics correcting hindfoot valgus or varus address the biomechanical drivers of the condition. An ankle brace provides external stability during rehabilitation and return to activity.
Corticosteroid injection:
An image-guided corticosteroid injection into the sinus tarsi provides significant relief in many patients and serves both a therapeutic and diagnostic role. It is particularly effective for cases driven by synovitis or acute inflammatory flares. Injections are used judiciously and are not typically repeated more than 2–3 times.
Extracorporeal Shockwave Therapy (ESWT):
A non-invasive option for chronic cases resistant to injection and physical therapy, ESWT stimulates tissue healing and has shown benefit in refractory hindfoot pain syndromes.
Surgical treatment (refractory cases):
When conservative measures fail after 3–6 months, arthroscopic debridement of the sinus tarsi — removing scarred tissue, synovitis, and fibrosis — relieves pain effectively in the majority of patients. If concurrent lateral ligament instability is confirmed on MRI and clinical examination, anatomic ligament reconstruction (Broström-Gould procedure) is performed simultaneously. Correction of underlying foot deformity with osteotomy may be required in patients with significant flatfoot or cavus contributing to the condition.
Get an MRI to Confirm Your Diagnosis
Before surgical planning or starting treatment, a clear MRI diagnosis ensures the right path forward. First Look MRI offers self-pay Foot and Ankle MRI scans — no doctor's order or insurance required — at our locations in Georgia, Texas, and Colorado.