FHL Tendinitis 2026: Causes & Treatment | Podiatrist

Flexor Hallucis Longus Tendinitis: Differential Diagnosis by Location

Flexor hallucis longus (FHL) tendinitis is one of the most commonly missed diagnoses in foot and ankle medicine — particularly in dancers, runners, and athletes who perform repetitive push-off. The FHL tendon runs from the deep posterior calf, through the tarsal tunnel behind the medial ankle, under the sustentaculum tali, and inserts at the base of the distal phalanx of the hallux. Pain can occur at three distinct points along this course, and each location points to a specific diagnosis and treatment. Confusing FHL tendinitis with sesamoiditis (both cause big toe pain with push-off) leads to months of incorrect treatment.

Pain Location	Most Likely Diagnosis	Distinguishing Feature	Clinical Test	Treatment
Posterior ankle / behind medial malleolus	FHL tendinitis at the fibro-osseous tunnel (most common site); FHL stenosing tenosynovitis; the tendon becomes inflamed where it passes through the narrow groove behind the medial malleolus	Pain with resisted plantarflexion of the great toe; pain that worsens when the ankle is dorsiflexed AND the big toe is dorsiflexed simultaneously (stretches the FHL maximally); “trigger toe” — intermittent locking of the great toe in flexion (tendon nodule catches in the tunnel)	FHL stretch test: with the ankle at neutral or dorsiflexion, passively extend the great toe → reproduces posterior ankle pain. Passive toe dorsiflexion is MORE painful than passive toe plantarflexion (opposite of sesamoiditis)	Activity modification; custom orthotic with Morton’s extension (limits 1st MTP dorsiflexion); PT — eccentric calf loading, ankle ROM; corticosteroid injection into the FHL tendon sheath; surgical FHL tendon release for stenosing tenosynovitis refractory to conservative care
Medial midfoot (under the navicular / arch)	FHL tendinitis at the sustentaculum tali; accessory navicular impingement on the FHL; tarsal tunnel syndrome with FHL involvement	Medial arch pain that worsens with push-off; pain may be accompanied by numbness or tingling (tarsal tunnel component); tender to palpation under the navicular or medial talus	Palpate the sustentaculum tali (medial heel, just below the medial malleolus); direct tenderness combined with FHL stretch test positive; ultrasound can visualize the FHL tendon sheath at this level	Orthotics supporting the medial arch; tendon sheath injection at the sustentaculum tali; tarsal tunnel decompression if nerve involvement confirmed; surgical FHL release if stenosing tenosynovitis confirmed at this level
Plantar hallux / sesamoid area (under big toe joint)	FHL tendinitis at the sesamoid level; sesamoiditis; hallux valgus with FHL bowstringing; the differential between FHL tendinitis and sesamoiditis at this level requires careful exam	FHL tendinitis: pain with resisted big toe plantarflexion AND passive toe dorsiflexion (stretching the FHL); no direct tenderness on the sesamoid bones themselves. Sesamoiditis: direct tenderness ON the sesamoid bones; pain with direct palpation more than with passive range of motion	Sesamoid palpation test: press directly on each sesamoid bone; significant pain = sesamoiditis. FHL test: pain with RESISTED great toe plantarflexion (contracting the FHL) = FHL tendinitis. Both can co-exist; differentiated with ultrasound (tendon pathology vs. bone pathology)	FHL: sesamoid-offloading orthotic reducing FHL load; avoid push-off activities; gentle FHL stretching. Sesamoiditis: see sesamoiditis treatment protocol. Both: rocker-sole shoe reduces 1st MTP dorsiflexion
Posterior heel (insertional / Achilles overlap area)	Posterior impingement syndrome (os trigonum); FHL tendinitis in the posterior ankle compartment; Achilles insertional tendinopathy — all can coexist in the same area	Pain behind the ankle with forced plantarflexion (pointing the foot) — NOT with dorsiflexion; common in ballet dancers (en pointe forces extreme plantarflexion); os trigonum (accessory bone behind talus) may be palpable	Posterior impingement test: forced plantarflexion of the ankle reproduces pain; compare to neutral or dorsiflexion (should be less painful). FHL component: add great toe dorsiflexion to the plantarflexion position → worsens pain = FHL impingement in the posterior ankle	Activity modification (avoid forced plantarflexion); corticosteroid injection into posterior ankle (os trigonum / FHL sheath); surgical os trigonum excision + FHL tenolysis for ballet dancers or athletes refractory to conservative treatment; 85-90% success with surgery for posterior impingement

FHL Tendinitis Treatment Protocol: 8-Week Conservative Plan

Phase	Timeline	Interventions	Activity Modification	Goal
Phase 1 — Offload	Weeks 1-3	Custom orthotic with Morton’s extension (rigid extension under the big toe that limits 1st MTP dorsiflexion = reduces FHL tensile load); rocker-sole shoe (HOKA); ice post-activity; NSAIDs × 7-10 days; rigid-soled footwear at all times	No barefoot walking; no demi-pointe (dancers); no running hills (increases push-off FHL demand); pool running or cycling as substitute	Reduce pain to ≤3/10 with normal ambulation
Phase 2 — Restore ROM	Weeks 3-5	Gentle passive big toe dorsiflexion stretching in a pain-free range; ankle ROM circles; intrinsic foot strengthening (NOT FHL-loading); towel scrunches; self-massage of the FHL tendon sheath behind the medial ankle	Gradual return to low-impact activity; swimming and cycling tolerated if pain-free; no impact activity yet	Full pain-free passive great toe dorsiflexion (to match contralateral side)
Phase 3 — Eccentric loading	Weeks 5-8	Heel raises with great toe extension (eccentric FHL loading on the descent); single-leg balance on rocker board; progressive resistance band great toe plantarflexion; advance to single-leg calf raise with emphasis on great toe push-off component	Return to running if pain ≤2/10; maintain orthotic in all running shoes; begin dance-specific exercises at 6-8 weeks if dancer	Pain-free single-leg heel raise × 25+; no locking or triggering of great toe; return to sport

Medically reviewed by Tom Biernacki, DPM — Board-Certified Foot & Ankle Surgeon · Updated May 2026 · Balance Foot & Ankle PLLC, Howell & Bloomfield Hills MI

Quick Answer

Flexor hallucis longus (FHL) tendinitis is irritation of the “big toe flexor” tendon as it passes through a tight fibro-osseous tunnel behind the ankle — commonly called “dancer’s tendinitis.” Pain is felt behind the inside ankle bone and at the back of the ankle, especially with rising on the toes, pointing the foot, or descending stairs. Most cases resolve in 6–12 weeks with rest, eccentric strengthening, custom orthotics, and avoiding repetitive plantar-flexion. Refractory cases respond to ultrasound-guided steroid into the sheath (never the tendon) or arthroscopic FHL release with os trigonum excision.

If you feel a deep ache behind your inner ankle bone every time you rise onto your toes — whether you’re a ballet dancer, a runner, a soccer player, or someone who simply walks a lot — you may be dealing with flexor hallucis longus (FHL) tendinitis. This is the powerful tendon that bends your big toe down, and it runs through one of the tightest tunnels in the human body. When it’s irritated, every push-off, stair descent, and toe-pointing motion lights it up. In our clinic, FHL tendinitis is one of the most commonly missed diagnoses in posterior ankle pain — often misdiagnosed as Achilles tendinopathy or posterior tibial tendinopathy for months before the right answer is found.

What Is FHL Tendinitis?

Flexor hallucis longus tendinitis is a stenosing tenosynovitis — inflammation and thickening of the FHL tendon and its sheath as the tendon passes through a tight fibro-osseous tunnel between the medial and lateral tubercles of the posterior talus. Because the tunnel is anatomically narrow, even small amounts of swelling cause friction with every step. It is the foot-and-ankle equivalent of De Quervain’s tenosynovitis at the wrist, and it earned the nickname “dancer’s tendinitis” because ballet’s relentless pointe and demi-pointe positions force the tendon to glide thousands of times against the tunnel walls.

FHL tendinitis exists on a spectrum. Stage 1 is simple irritation with sheath inflammation only. Stage 2 develops nodularity and triggering — the tendon may catch as you bend your big toe. Stage 3 is full stenosis with locking of the great toe. Catching FHL tendinitis at stage 1 means a 4–6 week recovery; missing it until stage 3 often requires surgery to release the tunnel and clean out the thickened sheath.

FHL Tendon Anatomy & Why It Gets Inflamed

The FHL tendon arises from the back of the lower fibula, descends behind the inside of the ankle, passes through a fibro-osseous tunnel between the medial and lateral talar tubercles, threads under the sustentaculum tali (a shelf of the heel bone), runs between the two sesamoid bones beneath the great toe, and finally inserts on the base of the distal phalanx. The total path is roughly 30 cm of tendon excursion with every full toe-flexion. The narrowest point — and the most common site of inflammation — is the posterior talus tunnel.

This tunnel becomes problematic when there is repetitive plantar-flexion (pointing the foot), when an accessory bone called the os trigonum is present, or when the tendon itself is hypertrophic. In ballet, soccer, and running athletes the tendon hypertrophies in response to load, but the tunnel does not enlarge to match — so what was previously a smooth glide becomes a tight squeeze, and tenosynovitis develops within weeks of an increase in training volume.

Symptoms of FHL Tendinitis

The hallmark symptom of FHL tendinitis is pain behind the medial malleolus (inside ankle bone) that worsens with great-toe push-off. Many patients describe a deep ache that feels too deep to be a sprain or a “regular” tendinitis. Some feel a snap, click, or actual locking of the great toe with motion. The pain is reproduced almost perfectly by rising on the toes or descending stairs.

• Posterior medial ankle pain — deep ache behind the inside ankle bone, often radiating into the arch.
• Pain with toe-off — rising on toes, walking up stairs, sprinting, or pushing off in basketball.
• Triggering or “catching” of the big toe (stage 2–3) — the toe may stick when bent.
• Crepitus — a palpable squeak or grinding behind the medial malleolus when bending the big toe.
• Posterior ankle pain in plantar-flexion (especially in dancers en pointe).
• Worse with footwear that has a stiff heel counter pressing on the tendon path.
• Morning stiffness with first-step pain, similar to but distinct from plantar fasciitis.

Causes & Risk Factors

FHL tendinitis is fundamentally an overuse condition driven by the combination of repetitive plantar-flexion and a tight anatomic tunnel. The single biggest risk factor is repetitive pointing of the foot — which is why ballet dancers (especially en pointe), gymnasts, soccer players, runners (particularly downhill runners), and basketball players make up the majority of cases in our clinic.

• Ballet, especially pointe and demi-pointe work — the classic cause, hence “dancer’s tendinitis.”
• Soccer, gymnastics, basketball, sprinting, and downhill running — sports with repetitive aggressive plantar-flexion.
• Os trigonum or large posterior talar process (Stieda process) — bony block that compresses the tendon.
• Cavus (high-arched) foot type — biases the tendon into chronic plantar-flexion.
• Sudden increase in training volume — the tendon hypertrophies faster than the tunnel can adapt.
• Poor footwear — stiff heel counters, worn shoes that no longer control pronation, dance shoes that don’t fit.
• Female sex and adolescence — ballet dancers ages 13–25 carry the highest risk demographics.

Os Trigonum Syndrome & Posterior Impingement

The os trigonum is an accessory bone present in roughly 7–14% of the population, formed when the lateral tubercle of the posterior talus fails to fuse during adolescence. When present, it sits exactly at the back of the ankle joint — right where the FHL tendon enters its tunnel. With aggressive plantar-flexion, the os trigonum gets pinched between the tibia above and the calcaneus below, causing posterior ankle impingement and irritating the FHL tendon at the same time. The two conditions almost always occur together.

If you have FHL tendinitis that fails 6 weeks of conservative care, an MRI almost always reveals an os trigonum or a prominent Stieda process as the bony driver. In our clinic, a lateral x-ray with the foot in maximal plantar-flexion is the single most useful test. Patients who have an os trigonum and continue to dance, sprint, or play soccer at high level are unlikely to fully resolve with non-operative care alone — arthroscopic os trigonum excision combined with FHL tunnel release is the definitive treatment.

⚠️ Key Takeaway

FHL tendinitis is the most commonly missed diagnosis in posterior ankle pain. If you’ve been treated for “Achilles tendinopathy” or “posterior tibial tendinopathy” for months without improvement, ask whether your pain is reproduced by resisted big-toe flexion. That single test points the spotlight at the right tendon.

How We Diagnose FHL Tendinitis

Diagnosing FHL tendinitis requires a focused exam, because the relevant tendon is buried deep behind the medial malleolus. The single most useful exam maneuver is the resisted great-toe flexion test — we ask you to bend your big toe down against our resistance, and we feel for tenderness and crepitus directly behind the medial malleolus. A second key test is the FHL stretch test: with the ankle dorsiflexed, we passively dorsiflex the great toe; reproduction of posterior medial pain is highly specific.

1. History & sport-specific questioning — we ask about ballet, gymnastics, sprinting, hill running, and recent training spikes.
2. Resisted great-toe flexion test — reproduces pain behind the medial malleolus.
3. Tomas’s plantar-flexion impingement test — passively forced ankle plantar-flexion reproduces posterior pain (positive in os trigonum syndrome).
4. Crepitus palpation — squeaking or grinding felt behind the medial malleolus during great-toe motion.
5. Weight-bearing x-ray (lateral with full plantar-flexion) — identifies os trigonum or Stieda process.
6. MRI — gold standard for tenosynovitis, partial tear, or longitudinal split tear of the FHL tendon.
7. Diagnostic ultrasound — allows dynamic imaging of triggering and guides therapeutic injection.

Differential Diagnosis: Conditions That Mimic FHL Tendinitis

Posterior medial ankle pain has a long differential, and FHL tendinitis lives in the middle of it. Treating the wrong tendon for months is the rule rather than the exception. Below are the conditions we work hardest to rule in or rule out before settling on FHL tendinitis.

• Posterior tibial tendinopathy (PTTD) — pain along the inside arch and ankle, often with arch collapse; tenderness more anterior to FHL.
• Tarsal tunnel syndrome — tibial nerve compression behind the medial malleolus; produces burning, tingling, and electrical pain rather than mechanical crepitus.
• Posterior ankle impingement — without FHL tendinitis; pain is more posterior and central, reproduced by forced plantar-flexion alone.
• Achilles tendinopathy — pain in the midline cord 2–6 cm above the heel; not reproduced by big-toe flexion.
• Retrocalcaneal bursitis — pain at the heel insertion of the Achilles; tenderness anterior to the Achilles, not behind the medial malleolus.
• Os trigonum syndrome (without FHL involvement) — uncommon; pain is purely posterior with plantar-flexion.
• Plantar fasciitis — first-step pain originating at the heel rather than behind the ankle.
• Stress fracture of the talus or sustentaculum tali — deep ache, point tenderness, MRI confirms.

Home Treatment That Actually Works

Most stage-1 FHL tendinitis resolves with disciplined home care over 4–6 weeks. The cornerstone is relative rest from the offending plantar-flexion activity — not complete shutdown, but a 4–6 week pause from pointe work, hill running, soccer kicking, and sprinting. We recommend swimming, cycling, and elliptical work to maintain fitness during the recovery window.

1. Relative rest from pointe, sprinting, and aggressive plantar-flexion for 4–6 weeks.
2. Ice behind the medial malleolus for 15 minutes after activity, 2–3 times per day.
3. NSAIDs for 7–10 days if your physician approves — reduces sheath inflammation.
4. Eccentric strengthening — controlled toe lowering off a step, 3 sets of 15 daily once acute pain resolves.
5. Calf stretching with knee straight and bent — 30 seconds × 4 reps, twice daily.
6. Topical analgesic — we have patients use Doctor Hoy’s Natural Pain Relief Gel behind the medial malleolus 2–3 times daily. (Affiliate disclosure: Amazon Associates, tag biernact-20.)
7. Supportive insoles — PowerStep Pinnacle Maxx with rearfoot support unloads the tendon by improving heel alignment.

In-Office Treatment Options

When 4–6 weeks of disciplined home care has not resolved the pain, we step up to in-office treatment. The treatment ladder progresses from biomechanical correction to image-guided injection to immobilization — only after these have been exhausted do we consider surgery.

• Custom orthotics with a deep heel cup and slight medial post to reduce the tendon’s working length.
• Physical therapy with eccentric loading, foot intrinsic strengthening, and Graston/instrument-assisted soft-tissue mobilization.
• CAM walker boot × 2–4 weeks for refractory acute cases — gives the sheath time to heal.
• Ultrasound-guided corticosteroid injection — placed into the tendon sheath, NEVER into the tendon itself; reserved for true tenosynovitis confirmed on MRI/US.
• Extracorporeal shockwave therapy (ESWT) — emerging evidence for chronic FHL tendinopathy.
• Platelet-rich plasma (PRP) — for partial tears or chronic tendinopathy that failed sheath injection.
• Activity modification counseling — especially critical for dancers and runners; we work with coaches to scale back without losing fitness.

Surgical Treatment

Surgery is reserved for FHL tendinitis that has failed at least 6 months of structured non-operative care, or for cases with mechanical locking, a documented os trigonum, or partial tendon tearing on MRI. Posterior arthroscopic FHL release combined with os trigonum excision is the modern gold standard, with return-to-dance or return-to-sport rates above 90% at 12 months.

• Posterior ankle arthroscopy (van Dijk technique) — two posterior portals, FHL tunnel release, os trigonum excision, synovectomy. Outpatient, immediate weightbearing in a boot.
• Open FHL release — a posteromedial incision, used when there is a high-grade longitudinal tear requiring direct repair or when arthroscopy is contraindicated.
• FHL tendon repair or tubularization — for partial-thickness split tears identified on MRI.
• Stieda process resection — for hypertrophy of the lateral talar tubercle when no true os trigonum is present.
• Recovery: boot for 2 weeks, sneakers at 4 weeks, full-impact return at 10–12 weeks; dancers typically return to pointe at 4–6 months.

Footwear & Activity Modification

The right footwear and activity adjustments can take a stage-1 FHL tendinitis from a 6-week saga to a 3-week annoyance. Avoid shoes with stiff, high heel counters that press directly on the tendon path. Choose shoes with a moderate (8–12 mm) heel-to-toe drop — minimalist zero-drop shoes are particularly bad for FHL tendinitis because they bias the tendon into chronic stretch.

Dancer-specific tip. Pointe shoes that don’t fit cause FHL tendinitis at extraordinary rates. Have your fitting checked every 6 months in adolescent dancers, and use Foot Petals or gel toe spacers to reduce intrinsic squeeze. Pair daily eccentric calf-and-toe drops with our recommended PowerStep Pinnacle Maxx in your street shoes — loading the tendon eccentrically while protecting it during walking is the fastest path to recovery.

🚨 Warning Signs to See a Podiatrist Now

Call our office at (810) 206-1402 if you experience locking or triggering of the great toe, inability to bend the big toe down, sudden severe posterior medial ankle pain after a pop, swelling combined with calf pain (DVT concern), or pain that has not improved after 6 weeks of conservative care. Mechanical locking can indicate a stage-3 stenosis that may need surgical release.

The Most Common Mistake We See

The most common mistake we see is treating FHL tendinitis as Achilles tendinopathy or posterior tibial tendinopathy for months without an MRI. The three conditions all live in the same neighborhood, but the right tendon to load is different for each. Patients show up after 6 months of unsuccessful eccentric heel drops and Achilles-targeted PT, only to have their pain reproduced perfectly by a single resisted big-toe flexion test in our exam room. The reason therapy didn’t work is simple — we were strengthening the wrong tendon.

The second mistake is injecting cortisone into the FHL tendon rather than into its sheath. Intratendinous cortisone weakens collagen and can precipitate a complete rupture — and ruptures of the FHL are devastating because the great toe loses propulsive flexion. Every steroid injection in this anatomy must be ultrasound-guided and clearly placed into the sheath. The third mistake is operating before MRI is obtained — without imaging it is easy to miss an os trigonum or a Stieda process that is the actual mechanical driver, and surgery without addressing the bony cause has high failure rates.

Frequently Asked Questions

How long does FHL tendinitis take to heal?

Stage-1 FHL tendinitis (sheath inflammation only) typically resolves in 4–6 weeks with relative rest, eccentric strengthening, and supportive footwear. Stage-2 (with nodularity or triggering) usually requires 8–12 weeks and often benefits from a sheath corticosteroid injection. Stage-3 (frank stenosis with locking) frequently requires arthroscopic FHL release and a 3–4 month recovery.

Can I keep dancing or running with FHL tendinitis?

Generally no — not at full intensity. The condition is fundamentally driven by repetitive plantar-flexion, so continuing to dance pointe or run hills typically prolongs symptoms by months. Most patients can maintain fitness with swimming, cycling, and elliptical work for 4–6 weeks, then ramp activity back up gradually as pain settles. Returning too early is the single biggest cause of recurrence.

Is FHL tendinitis the same as posterior ankle impingement?

They are related but distinct conditions, and they often coexist. Posterior ankle impingement refers to bony pinching of the posterior talus or os trigonum between the tibia and the calcaneus during plantar-flexion. FHL tendinitis is the tendon-and-sheath inflammation that occurs as a consequence. When both are present, both must be addressed at surgery.

Will an MRI show FHL tendinitis?

Yes — MRI is the gold-standard imaging test. It shows fluid in the FHL tendon sheath, thickening of the tendon, longitudinal split tears if present, and bony lesions like an os trigonum or Stieda process. We typically order an MRI for any FHL tendinitis that has not improved after 6 weeks of conservative care, especially before considering injection or surgery.

Should I get a cortisone shot for FHL tendinitis?

An ultrasound-guided cortisone injection placed into the FHL tendon sheath is reasonable when conservative care has stalled and MRI confirms tenosynovitis. We never inject cortisone directly into the tendon — that risks rupture. Patients can often return to lighter training within 7–10 days, but full pointe or hill running should wait at least 4 weeks post-injection.

When is surgery for FHL tendinitis necessary?

Surgery is indicated when (1) at least 6 months of structured conservative care has failed, (2) there is mechanical locking or triggering of the great toe, (3) MRI shows a partial-thickness longitudinal tear, or (4) an os trigonum or Stieda process is the dominant mechanical driver. Modern posterior arthroscopy releases the FHL tunnel and removes the bony block in a single 30-minute outpatient procedure.

The Bottom Line

Flexor hallucis longus tendinitis — “dancer’s tendinitis” — is one of the most overlooked causes of posterior medial ankle pain. Resisted great-toe flexion that reproduces pain behind the medial malleolus is the diagnostic key, and an MRI confirms tenosynovitis or an os trigonum. Most cases resolve in 4–12 weeks with relative rest, eccentric strengthening, and supportive footwear, with image-guided sheath injection and arthroscopic release reserved for refractory cases. If you have stubborn posterior ankle pain that has not responded to Achilles-targeted treatment, schedule a focused FHL exam with our team and we’ll get you the right answer.

Stubborn Posterior Ankle Pain?

Dr. Tom Biernacki and our board-certified team treat dancers, runners, and athletes with FHL tendinitis at our Howell and Bloomfield Hills offices. Same-week appointments available.

Call (810) 206-1402 · Howell & Bloomfield Hills, MI

Sources

1. Hamilton WG, Geppert MJ, Thompson FM. Pain in the posterior aspect of the ankle in dancers. Differential diagnosis and operative treatment. J Bone Joint Surg Am. 1996;78(10):1491-1500. PubMed
2. Kolettis GJ, Micheli LJ, Klein JD. Release of the flexor hallucis longus tendon in ballet dancers. J Bone Joint Surg Am. 1996;78(9):1386-1390. PubMed
3. van Dijk CN, Scholten PE, Krips R. A 2-portal endoscopic approach for diagnosis and treatment of posterior ankle pathology. Arthroscopy. 2000;16(8):871-876. PubMed
4. Carreira DS, Vora AM, Hearne KL, Kozy J. Outcome of arthroscopic treatment of posterior impingement of the ankle. Foot Ankle Int. 2010;31(11):1010-1015. PubMed
5. Eberle CF, Moran B, Gleason T. The accessory flexor digitorum longus as a cause of flexor hallucis syndrome. Foot Ankle Int. 2002;23(1):51-55. PubMed

Frequently Asked Questions — FHL Tendinitis

How long does flexor hallucis longus tendinitis take to heal?

Most cases of FHL tendinitis resolve in 6–12 weeks with appropriate conservative management: relative rest from aggravating activity (pointe work, jumping, push-off sports), a structured eccentric-strengthening program, and custom orthotics to offload the FHL. Insertional cases with os trigonum involvement may take 12–16 weeks. Surgical cases (arthroscopic FHL release + os trigonum excision) typically return to full activity in 3–4 months. Returning too early to push-off sports is the #1 cause of relapse.

What is the difference between FHL tendinitis and os trigonum syndrome?

They frequently coexist but are distinct entities. FHL tendinitis is inflammation of the tendon sheath, causing pain with active toe flexion and passive toe extension (the hallmark Triggering test). Os trigonum syndrome is posterior bony impingement from an accessory bone behind the talus — pain is reproduced by forced plantar flexion (like going on relevé). On MRI, FHL shows peritendinous fluid; os trigonum shows bone marrow edema. Both respond to steroid injection into the FHL sheath (not the tendon) and relative rest, but persistent os trigonum syndrome often requires excision.

Can I exercise with FHL tendinitis?

Yes — with modifications. Low-impact activities (swimming, cycling, upper-body strength work) are generally safe during recovery. Avoid repetitive pointe work, demi-pointe (rising on the ball of the foot), jumping, sprinting, and any activity that reproduces posterior ankle pain. A structured eccentric heel-drop program on a step can begin pain-free as early as week 2. Your podiatrist will clear you for progressive return to activity based on the Triggering test and patient-reported symptoms.

Is FHL tendinitis common in non-dancers?

Yes, though it is dramatically underdiagnosed outside dance medicine. FHL tendinitis occurs in runners (especially hill runners and forefoot strikers), soccer and football players, and any athlete who repeatedly loads the great toe flexor. It also appears in non-athletes following ankle sprains where swelling in the posterior compartment compresses the FHL sheath. When posterior ankle pain is labeled a “high ankle sprain” and does not improve, FHL involvement should be ruled out with ultrasound or MRI.

When is surgery recommended for FHL tendinitis?

Arthroscopic FHL release is recommended when conservative care fails after 3–6 months or when there is a mechanical block (triggering, stenosis, os trigonum). The procedure involves arthroscopic posterior ankle access, releasing the fibro-osseous roof of the FHL tunnel, and excising the os trigonum if present. Return to sport: 10–14 weeks for recreational athletes, 4–6 months for professional dancers. Open repair is reserved for complete FHL tears. Dr. Tom Biernacki performs this procedure at our Bloomfield Hills surgical facility. Call (810) 206-1402 to schedule a surgical evaluation.

Related Conditions

Watch: Flexor Hallucis Longus Pain — Best Treatment Options

Dr. Tom explains FHL tendinitis anatomy, why it is so frequently misdiagnosed as plantar fasciitis or Achilles tendinitis, and the specific rehabilitation protocol that works for runners, dancers, and athletes. Stenosing tenosynovitis and the “triggering” presentation are also covered.

Frequently Asked Questions