Health condition · Clinically reviewed
Flexor hallucis longus tendinopathy, the dancer’s tendinopathy — from injection to endoscopic FHL release.
Painful tendinopathy or triggering of flexor hallucis longus (FHL) behind the medial malleolus — the classic dancer’s tendinopathy. Modern stratified care: physiotherapy and ultrasound-guided injection; endoscopic FHL release for refractory cases.
Why trust this guide
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Clinically reviewed
Written by our editorial team and reviewed by a registered UK clinician before publication.
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Sourced from guidance
Every claim is checked against BOFAS, NICE and peer-reviewed sources you can see at the end.
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Current for 2026
Reflects current UK practice on ultrasound-guided injection and endoscopic hindfoot surgery.
Key facts
FHL tendinopathy at a glance.
The essentials, in plain English — what FHL tendinopathy is, why it hurts behind the medial malleolus, and what the modern treatment ladder looks like.
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Definition
FHL tendinopathy is a tendinopathy or stenosing tenosynovitis of flexor hallucis longus as it runs through the fibro-osseous tunnel behind the medial malleolus.
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Who it affects
Peak incidence in ballet dancers, gymnasts and footballers — repetitive plantarflexion loads the tendon in its posterior ankle tunnel.
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Coexists commonly
Often coexists with posterior ankle impingement or an os trigonum — the two problems share a mechanism and a treatment plan.
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Ultrasound first
Dynamic ultrasound is the diagnostic gold-standard — it shows tendon glide, triggering and tenosynovitis in real time.
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MRI role
MRI confirms tenosynovitis and reveals an os trigonum or bony impingement lesion when surgery is being considered.
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Modern surgery
Endoscopic FHL release is the modern minimally invasive treatment — small portals, quick recovery, low morbidity.
Why this guide matters
Physio and injection first, endoscopy last.
FHL tendinopathy usually settles with targeted rehab and a well-placed ultrasound-guided injection — endoscopic release is reserved for genuinely refractory or mechanical cases.
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Ultrasound is diagnostic
Dynamic ultrasound shows the tendon glide and any triggering in real time — the diagnostic test of choice.
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Image-guided injection is safer
Steroid placed in the FHL sheath under ultrasound guidance — never intra-tendinous — reduces the risk of tendon damage.
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Endoscopic release when refractory
When the tendon triggers or the sheath is stenosed, endoscopic release through small posterior portals is the modern solution.
How the diagnosis is made
From posterior ankle pain to a clear plan.
The steps a UK GP or foot and ankle team will normally follow, in order — so you know what to expect and why.
Phase 1 · Recognising
History, examination and provocation tests
Phase 2 · Confirming
Dynamic ultrasound and MRI for coexisting pathology
Phase 3 · Managing
Physio, injection, endoscopic release
- 01
Recognising
Symptom and activity history
Pattern of pain — dance, pointe work, running push-off — plus any clicking, catching or triggering of the big toe.
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Recognising
Palpation behind medial malleolus
Tenderness posterior to the medial malleolus, over the FHL tendon in its fibro-osseous tunnel.
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Recognising
FHL provocation test
Resisted big-toe flexion with the ankle held in plantarflexion reliably reproduces the pain.
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Confirming
Dynamic ultrasound
The diagnostic gold-standard — shows real-time tendon glide, triggering and tenosynovial fluid within the sheath.
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Confirming
MRI ankle
Confirms tenosynovitis, identifies an os trigonum and rules out osteochondral lesions before surgical planning.
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Managing
Assess coexisting impingement
Look for posterior ankle impingement or os trigonum — the two are commonly treated together.
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Managing
Foot and ankle surgery consultation
For refractory symptoms or a mechanical trigger — a hindfoot specialist to consider endoscopic release.
Typical timeline: 2–4 weeks from first appointment to a settled plan.
Symptoms
What FHL tendinopathy actually feels like.
The pattern is more telling than any single symptom — deep medial-posterior ankle pain, clicking or triggering of the big toe, worst on push-off or pointe.
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Medial posterior ankle pain
A deep pain behind and just below the medial malleolus, aggravated by push-off and pointe work.
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Big-toe stiffness
Stiffness or restricted movement of the hallux — the FHL controls big-toe flexion, so it feels reluctant.
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Clicking / catching
A clicking or catching sensation behind the medial malleolus as the tendon struggles to glide.
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Triggering of hallux
Frank triggering of the big toe — the tendon momentarily locks then releases with a snap.
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Dance / pointe pain
Symptoms typically worst in demi-pointe or pointe positions where FHL is loaded at end-range plantarflexion.
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Coexistent posterior impingement
Deep posterior ankle pain that mirrors or overlaps FHL symptoms — the two commonly go together.
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Recurrent symptoms
Symptoms that flare with return to dance or running despite rest — a pointer to mechanical FHL entrapment.
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Red flag
Acute FHL rupture with weakness of hallux flexion after a sudden push-off injury — urgent surgical review.
Treatment
How FHL tendinopathy is treated in the UK.
A staged approach — rehab and activity modification first, then ultrasound-guided injection, with endoscopic FHL release reserved for refractory or mechanical cases.
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Dance / activity modification
A short, targeted period away from the aggravating movement — pointe, demi-pointe or heavy running push-off — while the tendon settles.
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Physiotherapy (FHL glide + calf release)
Specific FHL tendon-glide work, calf release and intrinsic foot strengthening — the backbone of non-operative care.
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NSAIDs
A short course of anti-inflammatories for acute flares — useful adjunct while rehab and modification take effect.
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Ultrasound-guided steroid injection
Targeted injection into the FHL sheath under ultrasound guidance — for stubborn tenosynovitis, avoiding intra-tendinous placement.
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Boot immobilisation (acute flare)
A short period in a walker boot for a genuinely acute flare — offloading the tendon to allow the sheath to settle.
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Endoscopic FHL release
The modern minimally invasive procedure — small posterior portals, direct release of the FHL sheath, quick recovery.
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Open FHL debridement
Reserved for cases where endoscopic access is not appropriate — direct open release and debridement of diseased tendon.
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Combined FHL release + os trigonum excision
When posterior impingement coexists — a single endoscopic procedure to release the FHL and remove the os trigonum.
What this guide is based on
The sources behind every claim on this page.
UK national guidance and specialist society standards, current at the time of last review.
Key references
Guidelines and standards we relied on.
A quiet reminder
This guide is for information, not medical advice.
Your GP, physiotherapist or foot and ankle team knows your history and can tell you which parts apply to you. If in doubt, get seen.
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British Orthopaedic Foot and Ankle Society (BOFAS). Clinical standards for hindfoot pathology.
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NICE. Musculoskeletal guidance and tendinopathy pathways.
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American Orthopaedic Foot & Ankle Society (AOFAS). Patient information and clinical standards.
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Van Dijk CN. Endoscopic hindfoot technique for posterior ankle and FHL pathology.
Red flags
When posterior ankle pain is not just FHL tendinopathy.
Most cases settle with rehab and injection. These are the situations where a different diagnosis, or a post-op complication, needs to be considered.
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FHL rupture
A sudden pop with weakness of big-toe flexion — a complete tendon rupture needs urgent surgical review.
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Concomitant tibial nerve compression
Burning, tingling or numbness in the sole alongside FHL symptoms — consider tarsal tunnel involvement.
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Post-op tibial nerve injury
New numbness, burning or motor weakness after FHL surgery — needs prompt review by the operating team.
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Failed conservative therapy
Ongoing pain despite months of good rehab and injection — a trigger to escalate to specialist surgical opinion.
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Recurrent symptoms
Symptoms that repeatedly return after settling — suggests a fixed mechanical trigger that will not resolve without surgery.
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Post-op wound complication
Increasing pain, redness, discharge or fever after endoscopic or open release — contact the surgical team.
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Chronic ankle instability
Repeated ankle giving-way alongside FHL symptoms — needs a broader ankle assessment, not just tendon work.
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Missed osteochondral lesion
Deep, mechanical ankle pain that persists — MRI to rule out an osteochondral defect before further tendon treatment.
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Ankle arthritis differential
Diffuse ankle pain and stiffness that outlasts a simple tendinopathy pattern — consider early ankle arthritis.
Living with it
A patient tendon, but a very manageable one.
Four things that make the biggest difference day to day — rehab, load management, footwear and patient review.
A quiet reminder
Consistency beats intensity, every time.
Small, steady changes — kept up for weeks — do more than a heroic week that does not last.
- 01 Rehab
FHL glide work, daily
Specific tendon-glide exercises and calf release, done consistently — the tendon needs movement to recover its glide.
- 02 Load
Modify pointe and push-off
A short, planned reduction in aggravating loads — pointe, demi-pointe, heavy running — while the sheath settles.
- 03 Footwear
Support and cushioning
Supportive shoes for daily wear and a considered return to dance shoes — reduce end-range plantarflexion where you can.
- 04 Reviews
Reassess in weeks, not days
Rehab and injection take weeks to work — reassess at 6–12 weeks, and consider endoscopic release if symptoms persist.
Frequently asked
Everything we get asked about FHL tendinopathy.
Quick answers on diagnosis, injection, endoscopic release and return to dance.
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What actually is flexor hallucis longus tendinopathy?
It is a tendinopathy or stenosing tenosynovitis of the flexor hallucis longus tendon as it passes through the fibro-osseous tunnel behind the medial malleolus. Repetitive loading — particularly end-range plantarflexion in dancers — inflames the tendon sheath and can trigger or catch the tendon.
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Why is it called dancer’s tendinopathy?
Because it is classically seen in ballet dancers — the pointe and demi-pointe positions load the FHL tendon at end-range plantarflexion, exactly where it is most vulnerable in its fibro-osseous tunnel.
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How is it diagnosed?
Clinically, with tenderness behind the medial malleolus and pain on resisted big-toe flexion. Dynamic ultrasound is the diagnostic gold-standard because it shows the tendon glide and any triggering in real time. MRI is used to confirm tenosynovitis and identify a coexisting os trigonum.
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What is an endoscopic FHL release?
A modern minimally invasive procedure performed through small posterior ankle portals. The surgeon releases the fibro-osseous tunnel around the FHL tendon and, where present, removes an os trigonum in the same operation. Recovery is quicker than open surgery.
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Are steroid injections safe here?
Ultrasound-guided injection into the FHL sheath — not into the tendon itself — is a useful step for stubborn tenosynovitis. Image guidance is essential to place the steroid around the tendon and avoid intra-tendinous injection.
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What is the red flag I should not ignore?
A sudden pop with weakness of big-toe flexion after a forceful push-off suggests an acute FHL rupture and needs urgent surgical review. New numbness or burning in the sole alongside FHL symptoms may indicate tibial nerve involvement.
Related content
Keep reading.
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Posterior ankle impingement
Deep posterior ankle pain — often coexists with FHL disease.
Learn more -
Tarsal tunnel syndrome
Tibial nerve compression behind the medial malleolus.
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Foot MRI
MRI ankle and foot — tenosynovitis and os trigonum.
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