Sinus Tarsi Syndrome is a painful condition affecting the outside of the foot and ankle, specifically within the small canal between the talus and calcaneus bones known as the sinus tarsi. This space plays an important role in stabilizing the subtalar joint, which allows side-to-side movement of the foot. When inflammation, scarring, or instability occurs within this region, patients experience pain, swelling, and sometimes a sense of weakness or instability in the hindfoot.
How Common It Is and Who Gets It? (Epidemiology)
Sinus Tarsi Syndrome is relatively uncommon compared to other foot and ankle conditions but is often seen in active individuals, particularly athletes and dancers. It frequently develops after repeated ankle sprains or injuries that stretch or tear the stabilizing ligaments of the subtalar joint. People with flat feet (pes planus) or those who spend long hours on uneven surfaces are also more likely to develop this condition. Both men and women can be affected, though it is more frequent in middle-aged adults with chronic ankle instability.
Why It Happens – Causes (Etiology and Pathophysiology)
The condition can result from multiple underlying causes, including:
- Flatfoot Deformity: A fallen arch causes the talus and calcaneus bones to pinch the soft tissue within the sinus tarsi, leading to inflammation.
- Repetitive Sprains or Trauma: Repeated inversion injuries can damage the interosseous talocalcaneal and cervical ligaments, producing chronic instability and pain.
- Arthritis: Degenerative or inflammatory arthritis can affect the subtalar joint, leading to swelling within the sinus tarsi.
- Scar Tissue and Synovitis: Following injury or surgery, fibrotic tissue can form in the sinus tarsi, contributing to pain and limited motion.
- Vascular or Venous Changes: In some cases, venous congestion and fibrosis may increase pressure in the sinus tarsi, worsening pain.
How the Body Part Normally Works? (Relevant Anatomy)
The sinus tarsi is a small, cone-shaped space on the outer side of the hindfoot between the talus and calcaneus. It houses important stabilizing structures, including the cervical ligament (which limits inversion) and the interosseous talocalcaneal ligament (which prevents excessive eversion). It also contains fat, nerve endings, and blood vessels that help maintain proprioception and joint stability. In a healthy foot, these components work together to provide smooth motion and balance in the subtalar joint.
What You Might Feel – Symptoms (Clinical Presentation)
Common symptoms include:
- Pain or tenderness on the outer side of the foot, especially below the ankle bone.
- Swelling or fullness in the hollow between the ankle and heel bones.
- Discomfort when walking on uneven ground or when turning the foot.
- A sensation of instability or weakness in the ankle.
- Pain that worsens with activity and improves with rest.
In some cases, the swelling may resemble a cyst or small lump on the side of the foot.
How Doctors Find the Problem? (Diagnosis and Imaging)
Diagnosis is based on medical history, physical examination, and imaging studies.
- Clinical Examination: The doctor checks for tenderness over the sinus tarsi and evaluates ankle stability. Pain relief after a local anesthetic injection into the sinus tarsi confirms the diagnosis.
- X-rays: Used to identify flatfoot deformity, subtalar arthritis, or bone alignment issues.
- MRI: The best imaging tool for showing inflammation, ligament tears, or fibrosis within the sinus tarsi.
- Diagnostic Injections: A temporary reduction of pain after a local injection supports the diagnosis of Sinus Tarsi Syndrome.
Classification
Sinus Tarsi Syndrome can be broadly categorized by cause:
- Post-Traumatic STS: Occurs after sprains or ligament injuries.
- Mechanical STS: Caused by flatfoot deformity or subtalar instability.
- Degenerative or Inflammatory STS: Associated with arthritis or chronic inflammation.
Severity is often graded based on symptom duration, ligament injury, and joint degeneration.
Other Problems That Can Feel Similar (Differential Diagnosis)
Conditions that may mimic STS include peroneal tendonitis, lateral ankle sprains, subtalar arthritis, tarsal coalition, and ganglion cysts. Careful examination and imaging help distinguish between these conditions.
Treatment Options
Non-Surgical Care
- Activity Modification: Reducing high-impact activities or uneven terrain walking helps relieve stress.
- Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) reduce pain and swelling.
- Corticosteroid Injection: Direct injection into the sinus tarsi can relieve inflammation and confirm the diagnosis.
- Orthotics and Arch Supports: Custom inserts or medial wedges help realign the foot and reduce compression in the sinus tarsi.
- Bracing: Ankle-foot orthoses can provide additional support and rest to the subtalar joint.
- Physical Therapy: Focuses on strengthening, balance, and restoring range of motion while improving joint stability.
Surgical Care
Surgery is considered when non-surgical methods fail.
- Arthroscopic Debridement: A minimally invasive procedure to remove inflamed tissue, scar tissue, or debris from the sinus tarsi.
- Open Sinus Tarsi Decompression: Used in severe cases to remove extensive scar tissue or fibrotic fat.
- Flatfoot Correction: If deformity contributes to STS, surgical reconstruction may be necessary to restore alignment.
- Subtalar Fusion (Arthrodesis): For advanced arthritis, the joint is fused to eliminate motion and pain.
Recovery and What to Expect After Treatment
After surgery, patients typically use a protective boot and limit weight-bearing for several weeks. Stitches are removed around two weeks post-surgery, and gradual weight-bearing is reintroduced depending on the procedure. Physical therapy helps restore strength and balance. Most patients return to normal activity within 6–12 weeks, although full recovery may take longer after fusion procedures.
Possible Risks or Side Effects (Complications)
Potential complications include infection, nerve injury, persistent pain, stiffness, or recurrence of symptoms. Fusion surgery eliminates motion in the subtalar joint, which may shift stress to nearby joints over time.
Long-Term Outlook (Prognosis)
Most patients respond well to conservative treatment, achieving long-term pain relief and improved stability. Surgical outcomes are also favorable, particularly with arthroscopic techniques, where success rates often exceed 80–90%. Proper footwear, orthotic support, and maintaining a healthy weight help prevent recurrence.
Out-of-Pocket Costs
Medicare
CPT Code 28090 – Open Decompression/Excision of Sinus Tarsi Tissue: $106.42
CPT Code 28300 – Flatfoot Correction or Reconstruction (Calcaneal Osteotomy): $153.01
CPT Code 28725 – Subtalar Fusion for Advanced Cases: $182.74
Medicare Part B typically covers 80% of the approved cost for these procedures once your annual deductible has been met, leaving you responsible for the remaining 20%. Supplemental Insurance plans such as Medigap, AARP, or Blue Cross Blue Shield usually cover that 20%, minimizing or eliminating out-of-pocket expenses for Medicare-approved procedures. These supplemental plans coordinate with Medicare to fill the coverage gap and reduce patient responsibility.
If you have Secondary Insurance such as TRICARE, an Employer-Based Plan, or Veterans Health Administration coverage, it acts as a secondary payer. These plans generally cover any remaining balance, including coinsurance or small deductibles, which typically range from $100 to $300, depending on your plan and provider network.
Workers’ Compensation
If your Sinus Tarsi Syndrome developed as a result of a work-related injury, Workers’ Compensation will cover all associated medical expenses, including surgery, postoperative care, and rehabilitation. You will not have any out-of-pocket costs, as the employer’s insurance carrier pays for all covered treatments directly.
No-Fault Insurance
If your Sinus Tarsi Syndrome is related to an automobile accident, No-Fault Insurance will generally cover the total cost of treatment, including surgical decompression, reconstruction, or subtalar fusion. The only potential out-of-pocket cost may be a small deductible or co-payment, depending on your insurance policy.
Example
Karen Lopez developed Sinus Tarsi Syndrome after a chronic ankle injury and underwent open decompression of the sinus tarsi (CPT 28090) with an estimated Medicare out-of-pocket cost of $106.42. Since Karen had supplemental insurance through Blue Cross Blue Shield, her remaining balance was fully covered, leaving her with no out-of-pocket expenses for the surgery.
Frequently Asked Questions (FAQ)
Q. What is Sinus Tarsi Syndrome?
A. Sinus Tarsi Syndrome is a condition characterized by pain and tenderness in the sinus tarsi, a small canal on the outer side of the foot between the talus and calcaneus bones.
Q. What causes Sinus Tarsi Syndrome?
A. It is often caused by an inversion ankle sprain or repetitive overuse, leading to instability and inflammation of the structures within the sinus tarsi.
Q. What are the symptoms of Sinus Tarsi Syndrome?
A. Common symptoms include lateral foot pain, especially when walking on uneven surfaces, tenderness in the sinus tarsi area, and sometimes a feeling of instability in the foot.
Q. How is Sinus Tarsi Syndrome diagnosed?
A. Diagnosis is typically based on clinical examination and patient history, and may be confirmed with imaging such as MRI or diagnostic local anesthetic injection into the sinus tarsi.
Q. What nonsurgical treatments are available for Sinus Tarsi Syndrome?
A. Nonsurgical treatments include rest, ice, anti-inflammatory medications, physical therapy, corticosteroid injections, and ankle bracing.
Q. When is surgery considered for Sinus Tarsi Syndrome?
A. Surgery is considered if conservative treatments fail, and may involve debridement of the sinus tarsi, removal of inflamed tissue, or addressing any structural problems.
Q. How long does it take to recover from Sinus Tarsi Syndrome?
A. Recovery times vary, but many patients improve with conservative treatment over a few weeks to months, while surgical recovery can take longer depending on the procedure performed.
Q. Is physical therapy helpful for Sinus Tarsi Syndrome?
A. Yes, physical therapy can help strengthen the surrounding muscles, improve stability, and reduce inflammation, which may alleviate symptoms.
Q. Can orthotics help manage Sinus Tarsi Syndrome?
A. Yes, orthotic devices may help by providing better foot support and reducing strain on the affected area.
Q. What activities should be avoided with Sinus Tarsi Syndrome?
A. Activities that involve uneven surfaces, high impact, or repetitive ankle movements should be avoided to prevent aggravation of the condition.
Q. Who is most likely to develop sinus tarsi syndrome?
A. People with flat feet, chronic ankle instability, or repetitive strain from sports like basketball, soccer, or dancing are most at risk.
Q. Is surgery often needed?
A. No. Most patients improve with non-surgical treatment. Surgery is reserved for persistent or recurrent cases.
Q. Can orthotics really help?
A. Yes. Proper arch supports help restore alignment and reduce pressure on the sinus tarsi.
Q. Will sinus tarsi syndrome come back?
A. If underlying causes such as flatfoot deformity or instability are not corrected, symptoms can recur.
Summary and Takeaway
Sinus Tarsi Syndrome causes pain and swelling on the outer side of the foot due to inflammation or instability within the subtalar joint. It commonly results from flatfoot deformity, repetitive ankle injuries, or arthritis. Most cases respond well to non-surgical treatment, including orthotics, physical therapy, and injections. Surgical procedures, such as arthroscopic cleaning or deformity correction, are effective when conservative care fails. With proper management, long-term pain relief and stability can be achieved.
Clinical Insight & Recent Findings
A recent study critically reviewed what is known about Sinus Tarsi Syndrome (STS), finding that the term is often used too broadly to describe pain on the outer side of the foot without pinpointing its true cause.
The authors noted that this pain can result from a variety of issues—including ligament injury, instability of the subtalar joint, inflammation, nerve irritation, vascular changes, or soft-tissue impingement. Because of this complexity, they recommend moving away from using “STS” as a blanket term and instead identifying the specific underlying problem through detailed examination, imaging, or subtalar arthroscopy.
This approach allows for more precise and successful treatment—whether through orthotics, therapy, injections, or minimally invasive arthroscopic surgery that can both diagnose and relieve pain. (“Study on defining and treating sinus tarsi pain – see PubMed.”)
Who Performs This Treatment? (Specialists and Team Involved)
Sinus Tarsi Syndrome is managed by an orthopedic foot and ankle surgeon or a podiatrist. The care team may include radiologists, physical therapists, and anesthesiologists who assist with imaging, rehabilitation, and pain control.
When to See a Specialist?
You should consult a specialist if you experience persistent pain, swelling, or instability in the outer ankle that lasts longer than two weeks or interferes with walking and daily activities.
When to Go to the Emergency Room?
Go to the emergency room if you have severe foot pain after a fall or twisting injury, sudden deformity, inability to bear weight, or redness and warmth suggesting infection.
What Recovery Really Looks Like?
Recovery often involves several weeks of rest and rehabilitation. Mild cases improve within a few weeks of conservative care, while post-surgical recovery may take up to three months. Ongoing physical therapy and supportive footwear help maintain long-term improvement.
What Happens If You Ignore It?
Untreated STS can cause chronic pain, recurring ankle instability, and difficulty walking on uneven surfaces. Over time, it can contribute to subtalar arthritis or altered gait mechanics.
How to Prevent It?
Wearing supportive footwear, strengthening ankle stabilizer muscles, and using orthotics for flatfoot deformities can reduce risk. Avoiding uneven terrain and warming up before athletic activity also help prevent ligament injuries.
Nutrition and Bone or Joint Health
A diet rich in calcium, vitamin D, and protein supports healthy bones and soft tissue recovery. Adequate hydration and maintaining a balanced body weight reduce excess stress on the foot and ankle.
Activity and Lifestyle Modifications
Low-impact activities like swimming, cycling, or yoga can help maintain fitness while minimizing strain on the subtalar joint. Supportive shoes, proper arch supports, and regular stretching of the calf and foot muscles are key to preventing recurrence and maintaining long-term foot health.
Dr. Mo Athar
