Sinus Tarsi Syndrome (STS) is a condition that causes pain and sometimes swelling in the sinus tarsi, a small tunnel-like space on the outer (lateral) side of the hindfoot. People usually feel the pain just below and slightly in front of the bony knob on the outside of the ankle (the lateral malleolus). It often feels sore to touch, and many people describe a sense of the ankle feeling unstable or “wobbly”, especially on uneven ground.
STS most commonly develops after an inversion ankle sprain (where the foot rolls in and the ankle ligaments are strained). Even once the initial sprain feels “better”, the subtalar joint (the joint between the talus and the calcaneus) can remain irritated or less stable, and tissues within the sinus tarsi can become inflamed or scarred. STS can also develop gradually with overuse, particularly when there is overpronation (the foot rolling inward too much), flat feet, or a rapid increase in walking or running loads.
The sinus tarsi is more than just an empty space. It contains a fat pad, blood vessels, nerves, and several stabilising ligaments that help your foot make tiny balance adjustments. When these structures are irritated, STS can make everyday tasks like walking on grass, turning quickly, or running on trails feel painful and unreliable.
Physiotherapy for sinus tarsi syndrome is focused on three things:
- Settling pain by reducing the loads and positions that irritate the sinus tarsi
- Restoring stability and control around the ankle and subtalar joint through targeted strengthening and balance training, and
- Correcting contributing factors such as overpronation, reduced calf and foot strength, or poor footwear choices.
When done well, STS rehab often improves both pain and confidence in the ankle.
Key Facts
- A study reviewing people who had lateral ankle sprains found that around 22% (about 1 in 5) later developed sinus tarsi syndrome. 🔗
- Research shows steroid injections can help in the short term, but symptoms return in about 2 out of 3 people within a year, suggesting injections may not address the underlying causes such as ankle stability or movement control. 🔗
- Sinus tarsi syndrome is described as lateral hindfoot pain and tenderness, commonly associated with ligament and soft tissue injury in the sinus tarsi on imaging. 🔗
Risk Factors
- History of inversion ankle sprain or repeated ankle sprains, especially if rehab was incomplete.
- Subtalar instability or poor balance and proprioception after injury.
- Overpronation, flat feet, or foot posture that increases rearfoot eversion during gait.
- Rapid increase in walking, running, jumping, or return-to-sport training loads.
- Footwear with poor rearfoot support or worn-out shoes that reduce stability.
- Weakness or endurance deficits in the calf, peroneals, and foot stabilisers.
Symptoms
- Pain below and slightly in front of the outer ankle bone (lateral malleolus), often described as a deep ache on the outside of the hindfoot.
- Pain that worsens on uneven or unstable surfaces (grass, trails, sand) or with quick direction changes.
- A feeling of instability, “giving way”, or lack of trust in the ankle, especially when turning or walking on slopes.
- Tenderness when pressing into the sinus tarsi region, sometimes with a puffy or “lumpy” feel.
- Pain during or after activity, sometimes with lingering soreness later that day or the next morning.
- Swelling around the outer hindfoot in more irritable flare-ups.
Aggravating Factors
- Walking on uneven surfaces, trails, grass, sand, or cambered roads where the ankle has to stabilise constantly.
- Pivoting and cutting activities (football codes, netball, basketball) or quick direction changes.
- Running volume spikes or returning to sport too quickly after an ankle sprain.
- Prolonged standing and walking when the foot rolls in and loads the subtalar region repeatedly.
- Unsupportive footwear that allows excessive pronation or poor rearfoot control.
Causes
Sinus tarsi syndrome usually develops when the tissues inside the sinus tarsi become irritated. The most common pathway is after an inversion ankle sprain. With a sprain, structures that stabilise the hindfoot can be strained, and the subtalar joint may move less smoothly. This can lead to inflammation, synovitis (irritation of joint lining), bleeding into the area, and later scar tissue that makes the space sensitive. Many people feel the sprain “healed”, but the ankle can still have subtle instability and reduced proprioception (the body’s joint position awareness), which keeps stressing the sinus tarsi with everyday walking and sport.
Another common driver is overuse combined with overpronation or flat feet. When the foot rolls in excessively, the subtalar joint and sinus tarsi region can be repeatedly compressed and twisted. Over time, the tissues can become reactive and painful, especially when training loads increase quickly or footwear is not supportive.
STS can also be linked with other conditions that change hindfoot mechanics (such as posterior tibial tendon dysfunction and adult-acquired flat foot), and it may occur alongside peroneal tendon irritation, lateral ankle ligament pain, or anterolateral impingement. This is why a physiotherapy assessment matters: the best rehab plan depends on what is actually driving the irritation in your case.
How Is It Diagnosed?
Diagnosing sinus tarsi syndrome involves a detailed history and a targeted physical examination. Your physiotherapist will ask about previous ankle sprains, how well the ankle recovered, current activity levels, footwear, and the specific situations that flare pain (uneven ground is a classic trigger). They will examine the exact pain location, swelling, and tenderness within the sinus tarsi region, and they will assess ankle and subtalar joint movement, ligament stability, foot posture, and single-leg control.
Because other conditions can mimic STS, your physiotherapist will also screen for alternative or co-existing causes of lateral ankle pain, such as lateral ligament injury (ATFL/CFL), peroneal tendinopathy, anterolateral impingement, subtalar arthritis, stress injury, or referred pain. Functional testing often includes balance and proprioception tests, hopping or change-of-direction tolerance (if appropriate), and gait or running assessment to identify mechanical contributors such as overpronation.
If symptoms are persistent or the diagnosis remains unclear, imaging and medical review may be recommended. In some cases, a diagnostic local anaesthetic injection into the sinus tarsi (performed by a doctor) can help confirm whether the sinus tarsi is the main pain generator if the pain temporarily settles after the injection.
Investigations & Imaging
- X-ray
- Used mainly to rule out fractures, arthritis, or bony abnormalities when symptoms are persistent or the history suggests a bony injury. X-rays do not show soft tissue inflammation within the sinus tarsi.
- Ultrasound
- May identify synovitis or fluid and can assess nearby tendons, but it can be less definitive for deep sinus tarsi structures compared with MRI.
- MRI
- Useful to visualise sinus tarsi inflammation, scar tissue, ligament integrity, subtalar joint synovitis, and bone marrow changes, and to assess co-existing injuries when symptoms do not resolve as expected.
Physiotherapy Management
Physiotherapy for sinus tarsi syndrome targets the reasons the sinus tarsi is being irritated. For many people, this means treating the after-effects of an ankle sprain: lingering instability, reduced proprioception, and poor load control through the hindfoot. For others, it means correcting mechanics such as overpronation and building foot and ankle strength so the subtalar joint is better supported during walking and sport.
Your physiotherapist will usually combine load modification (to settle pain), progressive strengthening (to build capacity), and balance training (to restore stability and confidence). Supportive strategies such as taping, braces, and orthotics may be used to reduce symptoms while you rebuild strength. The key goal is to stop the cycle where the ankle feels unstable, gets overloaded on uneven surfaces, and stays inflamed.
Exercise
Physiotherapy exercises are chosen to improve control around the ankle and subtalar joint without repeatedly flaring lateral hindfoot pain. Early on, your physiotherapist may start with simple strength and control drills such as resisted ankle eversion (peroneal strengthening), calf raises with good alignment, and foot intrinsic strengthening to improve midfoot stability and reduce excessive rearfoot motion.
As symptoms settle, exercises progress to single-leg strength and endurance work because STS often shows up when the ankle has to stabilise the body over one leg. This can include step-down control, single-leg calf raises, and controlled lateral movement drills that mimic sport demands. Your physiotherapist will also emphasise hip and trunk control if they identify poor lower-limb alignment contributing to excessive rearfoot stress.
In later stages of rehab, balance and impact progression become more specific. This may include hopping progressions, change-of-direction drills, and graded return to running, introduced only when the ankle is no longer reactive on daily walking and uneven ground exposure. The goal is to return you to sport without bringing back the same instability-and-flare pattern.
Activity Modification
Activity modification for STS is about reducing the exact loads that irritate the sinus tarsi while keeping you active. Common triggers include uneven surfaces, trail running, pivoting sports, and sudden increases in walking or running. Your physiotherapist will help you temporarily reduce these triggers and replace them with lower-irritation options such as flat-surface walking, cycling, swimming, or gym-based conditioning.
If STS follows an ankle sprain, your physio will usually advise against returning to full training purely based on time. Instead, return is guided by function: pain-free walking, improved balance, improved single-leg strength, and reduced tenderness in the sinus tarsi region. For athletes, this often involves a staged reintroduction of training elements: straight-line running first, then gentle change of direction, then full training and game exposure.
A practical rule used in physiotherapy is monitoring the 24-hour response. If pain and swelling are clearly worse the next day, the load was too high and needs to be adjusted.
Manual Therapy
Manual therapy may help when joint stiffness or soft tissue restriction is contributing to abnormal subtalar motion and ongoing irritation. Physiotherapists may use joint mobilisation techniques to improve ankle and subtalar movement quality and soft tissue techniques to reduce tightness in the calf and lateral lower-leg muscles that can alter foot mechanics.
Manual therapy can also provide short-term pain relief, which often improves your ability to complete balance and strengthening exercises with better quality. In STS, manual therapy is most useful when it supports a broader plan that rebuilds stability and addresses contributing mechanics, rather than being used as a stand-alone treatment.
Postural Retraining
Postural retraining in sinus tarsi syndrome is really about movement retraining, especially how the foot and ankle behave in single-leg stance, walking, running, and turning. Many people with STS either collapse into pronation (which stresses the sinus tarsi) or avoid loading the outside of the heel (which can create other compensations). Your physiotherapist will coach alignment and foot control strategies that reduce repeated hindfoot irritation.
For runners, this may include technique tweaks such as reducing overstriding, adjusting cadence, or changing how quickly you return to trails and cambered roads. For field athletes, it can include landing control, deceleration drills, and sport-specific footwork, progressed gradually as stability returns.
Bracing & Taping
Taping and bracing are commonly used in sinus tarsi syndrome rehab, particularly when symptoms follow an ankle sprain and instability is present. A physiotherapist may tape the ankle and rearfoot to limit excessive subtalar motion and provide immediate confidence on uneven surfaces. This can reduce pain while you rebuild strength and proprioception.
Orthotics or arch supports may be helpful when overpronation or flat feet are major contributors. By supporting the arch and improving rearfoot alignment, orthotics can reduce repeated strain through the sinus tarsi. Importantly, physiotherapists use these supports as a bridge, not a crutch. The long-term aim is still to restore strength, endurance, and control so the ankle can cope without constant external support.
Footwear advice is part of this conversation. Shoes with better rearfoot stability and a secure heel counter (without rubbing) can reduce symptoms in people whose STS is driven by pronation and instability.
Heat & Ice
Ice can help reduce pain after an irritating day on your feet or after a training session that flared symptoms. Short applications can be useful, especially early on. Heat is less commonly used for STS itself, but may be useful for calf muscle tightness if stiffness is affecting ankle mechanics.
Tens
TENS may be used as a short-term pain relief tool when lateral hindfoot pain is limiting walking or sleep. In STS, it is generally an adjunct to help you stay active and complete your rehab exercises rather than a primary solution.
Education
Education is a major part of physiotherapy for sinus tarsi syndrome. Your physiotherapist will explain why symptoms often flare on uneven surfaces and why the ankle can feel unstable even after the initial sprain pain has settled. You will learn how to pace your activity, how to progress exposure to uneven ground, and how to recognise early warning signs of a flare so you can adjust before symptoms snowball.
Education also includes footwear guidance, the role of taping and orthotics, and realistic expectations. Many people improve over weeks with consistent rehab, but persistent cases often need a longer, structured plan, particularly if there is longstanding instability or significant overpronation that has not been addressed.
Other
Other physiotherapy management may include a guided return-to-sport program, graded trail exposure for runners, and coordination with your GP if anti-inflammatory medication or injection is being considered. If your physiotherapist suspects significant subtalar pathology, coalition, arthritis, or persistent instability that is not responding to rehab, they may recommend imaging and referral to a sports doctor or orthopaedic specialist.
Other Treatments
Other treatments may include short-term use of NSAIDs as advised by a doctor to reduce pain and inflammation. In more persistent cases, a doctor may consider a corticosteroid injection into the sinus tarsi. Injections can provide symptom relief for some people, but they do not automatically address underlying issues such as instability or overpronation, which is why physiotherapy is still important alongside medical management.
Footwear modifications can make a meaningful difference, particularly when poor shoe stability or worn-out shoes are contributing. In selected cases, clinicians may also use imaging-guided injections or pursue further investigation if another diagnosis is suspected.
Prognosis & Return to Activity
The outlook for sinus tarsi syndrome is generally positive when the main drivers are identified and addressed. Mild cases, particularly early after a sprain, can improve within weeks when load is modified and stability is rebuilt. More persistent cases may take longer, especially when there is long-standing ankle instability, repeated sprains, or significant overpronation and poor foot control.
Return to activity is usually guided by function-based milestones rather than a fixed timeline. Key milestones often include: comfortable walking on flat ground, improved tolerance to uneven surfaces, minimal tenderness in the sinus tarsi region, good single-leg balance and control, and the ability to progress running and cutting drills without next-day flare.
If symptoms are not improving with appropriate physiotherapy, reassessment is important to confirm the diagnosis and investigate co-existing problems such as peroneal tendon irritation, anterolateral impingement, or subtalar joint pathology.
Complications
- Chronic lateral hindfoot pain and persistent swelling if instability and mechanical contributors are not addressed.
- Recurrent ankle sprains due to unresolved balance and proprioception deficits.
- Reduced participation in sport, trails, and uneven-ground activities due to loss of confidence and pain flare-ups.
- Secondary issues such as peroneal tendinopathy or altered gait-related pain if compensation patterns persist.
Preventing Recurrence
- Complete ankle sprain rehab properly. Restoring balance, proprioception, and single-leg strength reduces the risk of ongoing subtalar irritation and STS after a sprain.
- Progress uneven-surface exposure gradually. If trails and grass flare symptoms, build tolerance in steps rather than returning suddenly to long uneven sessions.
- Address overpronation drivers with strengthening and (when helpful) orthotic or footwear support to reduce repetitive subtalar stress.
- Maintain calf, peroneal, and foot strength year-round, especially if you have a history of sprains or lateral ankle instability.
When to See a Physio
- If lateral hindfoot pain and “wobbliness” persist more than 2 to 3 weeks after an ankle sprain.
- If you have repeated ankle sprains or feel unstable on uneven ground, as targeted balance rehab can reduce recurrence.
- If pain is worsening, swelling is increasing, or you cannot return to normal walking, as imaging or medical review may be needed.
- If you suspect overpronation or flat feet are contributing and you want guidance on orthotics, footwear, and foot strengthening.