Sinus Tarsi Syndrome (STS). A common but often overlooked cause of pain and instability on the outside of the ankle

What Is the Sinus Tarsi?

The sinus tarsi is a small tunnel-like space located on the outer front side of the ankle, between the ankle bone (talus) and the heel bone (calcaneus).

You can usually feel this area by sliding your fingers slightly forward from the outer ankle bone.

Inside the sinus tarsi are important structures that help control ankle stability, including:

• Key ankle ligaments

• Joint capsule tissue

• Fat tissue that absorbs stress

• Small blood vessels

• Sensory nerve branches supplying the foot

Because many sensitive structures pass through this small space, irritation here can easily cause pain.

What Causes Sinus Tarsi Syndrome?

Sinus tarsi syndrome is most commonly caused by abnormal ankle mechanics, which lead to excessive compression or stretching inside the sinus tarsi.

This irritation may result from:

• Flat feet or high-arched feet

• Chronic ankle instability after ankle sprains

• Repeated ankle sprains

• Poor or restrictive footwear that alters ankle movement

Other possible causes include:

• Degenerative changes after ankle fractures

• Osteoarthritis of the ankle or subtalar joint

• Cysts forming inside the sinus tarsi

If left untreated, long-standing sinus tarsi syndrome can lead to:

• Ligament damage

• Cartilage wear

• Scar tissue formation

• Degenerative and even necrotic changes

  
  

Symptoms – How It Usually Feels

The main symptom is pain on the outer front side of the ankle, especially when:

• Standing

• Walking

• Running

• Walking on uneven ground

Pain characteristics may include:

• Inflammatory pain with stiffness

• Temporary relief after warming up

• Burning pain or tingling if nerves are irritated

• Sharp stabbing pain in more advanced cases

• A feeling of ankle instability

With long-lasting symptoms, you may notice:

• Swelling

• Redness

• Warmth around the sinus tarsi

Symptoms often start mildly and gradually worsen over time, or remain at a low but persistent level for months.

Diagnosis

Diagnosis should always begin with a posture and movement assessment.

A physiotherapist or doctor will assess:

• Foot and ankle alignment

• Ankle stability

• Walking and loading patterns

Clinical tests include:

• Palpation (pressing) over the sinus tarsi

• A positive Tinel-Hoffmann sign (tingling when tapping the area)

• Testing movement in the upper and lower ankle joints to detect instability

A helpful diagnostic tool is a local anesthetic injection into the sinus tarsi:

• If pain significantly decreases or disappears, the diagnosis is very likely correct

Imaging:

• MRI helps evaluate deeper structures

• Arthroscopy is considered the most accurate diagnostic method

  
  

Physiotherapy Treatment

Treatment should always start with removing the provoking factor.

This may include:

• Changing footwear

• Using supportive insoles

Physiotherapy then focuses on:

• Correcting foot and ankle mechanics

• Strengthening stabilizing muscles

• Stretching tight tissues

• Improving balance and proprioception (deep joint sense)

To reduce inflammation and pain, treatment may include:

• Manual therapy

• Physical therapy modalities

• Anti-inflammatory medication (if necessary)

  
  

Surgical Treatment

Surgery is considered when:

• There are no obvious mechanical causes

• A cyst is suspected

• Conservative treatment fails to improve symptoms

Arthroscopic surgery may involve:

• Cleaning damaged tissue

• Removing scar tissue and inflammatory overgrowth

In severe cases, fusion of the talus and calcaneus may be required.

When to See a Physiotherapist

You should seek professional assessment if you have:

• Persistent outer ankle pain

• Pain after repeated ankle sprains

• Ankle instability or lack of confidence when walking

• Pain that does not improve with rest

Early diagnosis significantly improves recovery outcomes.

Why Sinus Tarsi Syndrome Is Often Missed

STS is often confused with:

• Lateral ankle sprain

• General ankle pain

• Peroneal tendon issues

Without proper assessment, treatment may focus on the wrong structure.

References

1. Pisani G. et al. Sinus Tarsi Syndrome and Subtalar Instability. 2005.

2. Helgeson K. Examination and Intervention for Sinus Tarsi Syndrome. 2009.

3. Klausner V. B. et al. The Sinus Tarsi Syndrome. 2000.

4. Li S-K. et al. Arthroscopic Treatment for Sinus Tarsi Syndrome. 2018.

5. Hertel J. Functional Instability Following Lateral Ankle Sprain. 2000.