Medically reviewed by Dr. Tom Biernacki, DPM
Board-certified podiatric surgeon | Balance Foot & Ankle, Howell & Bloomfield Hills, MI
Last reviewed: May 2026
Quick answer: Fhl Tendinitis can significantly impact your daily life and mobility. Our Michigan podiatrists provide expert evaluation and evidence-based treatment — from conservative care to minimally invasive procedures — to relieve your symptoms and restore function. Same-day appointments available in Howell and Bloomfield Hills, MI.
| FHL Tendinitis Grade | Pathology | Symptoms | MRI Finding | Treatment Approach |
|---|---|---|---|---|
| Grade 1 — Mild | Peritendinous inflammation | Pain with activity, minimal rest pain | Increased signal, intact tendon | RICE, NSAIDs, activity modification |
| Grade 2 — Moderate | Partial tendon degeneration | Pain during and after activity | Intratendinous signal change <50% | PT, eccentric loading, orthotic |
| Grade 3 — Severe | Significant tendinosis ± partial tear | Pain at rest, functional limitation | Signal change ≥50%, possible gap | Boot immobilization, consider surgery |
| Grade 4 — Complete Tear | Full-thickness rupture | Loss of big toe push-off strength | Full-thickness discontinuity | Surgical repair or tendon transfer |
| Stenosing Tenosynovitis | Tendon nodule in FHL tunnel | Triggering / locking of big toe | Nodule at fibro-osseous tunnel | Endoscopic or open release |
| Rehabilitation Phase | Weeks | Exercises | Load Level | Goal |
|---|---|---|---|---|
| Acute / Offload | 1–2 | Ankle circles, toe range-of-motion (pain-free only) | None | Reduce inflammation, maintain joint mobility |
| Isometric Loading | 3–4 | Isometric big-toe flexion against resistance band | Low | Begin tendon loading without dynamic stress |
| Isotonic Strengthening | 5–8 | Towel toe curls, marble pickups, short-foot exercise | Moderate | Tendon hypertrophy, intrinsic foot strength |
| Eccentric Loading | 9–12 | Eccentric heel raises, single-leg tip-toe balance | Progressive | Tendon remodeling, sport-specific load tolerance |
| Sport-Specific Return | 13–16 | Relevé (dancers), calf-raise progressions, plyometrics | High | Return to full performance without pain |
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FHL tendinitis (flexor hallucis longus tendinitis) is inflammation of the tendon that curls your big toe. It causes pain along the inner ankle, behind the ankle bone, or under the big toe — typically in dancers, gymnasts, and runners. The hallmark symptom is a painful clicking or triggering of the big toe with motion. Most cases resolve with activity modification, eccentric strengthening, and proper footwear, but a tendon nodule causing triggering may require an injection or surgery.
Your big toe clicks, catches, or locks when you push off during a run, land from a jump, or rise onto pointe. The pain trails behind your ankle bone down into the arch, sometimes burning, sometimes aching — always worse with the first few steps after rest and after high-demand activity. This is the classic story of flexor hallucis longus (FHL) tendinitis, a condition that is dramatically over-diagnosed as “plantar fasciitis” or “posterior tibial tendinopathy” in patients who never get better because they’re being treated for the wrong thing. In our clinic, we see FHL tendinitis most often in ballet dancers and distance runners, and the key to fixing it is recognizing the tendon involved and addressing the mechanical reason it became inflamed.
What Is FHL Tendinitis
The flexor hallucis longus (FHL) tendon is the powerhouse tendon of the big toe — it originates in the deep posterior compartment of the lower leg, travels behind the ankle, passes through a fibro-osseous tunnel beneath the sustentaculum tali of the calcaneus, and inserts into the base of the distal phalanx of the hallux. In practical terms, this tendon performs the powerful push-off function of the big toe during walking, running, and jumping — and it generates more force per cross-sectional area than almost any other tendon in the lower extremity. FHL tendinitis is inflammation and degeneration of this tendon anywhere along its course — at the ankle (most common), within the tarsal tunnel, or at its insertion.
The condition is categorized into zones based on anatomical location. Zone 1 (posterior ankle/fibro-osseous tunnel) is the most common — this is where the tendon is most constrained and most vulnerable to friction and tenosynovitis. Zone 2 (beneath the sustentaculum tali in the foot) causes pain in the medial arch. Zone 3 (the “knot of Henry” where FHL crosses the flexor digitorum longus) causes pain in the midfoot. Zone 4 (at the hallux insertion) is less common and typically a result of sesamoid pathology.
Anatomy: Why FHL Gets Inflamed
The FHL tendon has a unique anatomical vulnerability: unlike most tendons in the foot that course through relatively open channels, the FHL passes through a tight fibro-osseous tunnel at the posterior ankle. This tunnel is bordered by the medial and lateral talar tubercles — and the space within it is extremely constrained. When the ankle repeatedly moves from plantarflexion to dorsiflexion (as in ballet, running, or jumping), the FHL tendon slides back and forth through this narrow channel thousands of times per training session. Friction generates tenosynovitis (inflammation of the tendon sheath), and over time, the tendon itself becomes thickened with areas of mucoid degeneration.
A tendon nodule — a focal thickening of the tendon — can develop at Zone 1. When this nodule tries to pass through the fibro-osseous tunnel, it catches and triggers (produces an audible or palpable click). This is called “hallux saltans” or triggering hallux, and it is pathognomonic (diagnostic in itself) for FHL tendinopathy with nodule formation. In our clinic, when a patient demonstrates triggering of the hallux during dorsiflexion-plantarflexion testing, we have a definitive answer: this is FHL tendinopathy at Zone 1.
Symptoms of FHL Tendinitis
FHL tendinitis produces a highly recognizable symptom pattern once you know what to look for. The challenge is that many patients — and some clinicians — miss it because the pain can be felt in multiple locations depending on which zone is affected. Understanding the location–symptom relationship is the key to not missing this diagnosis.
- Posterior medial ankle pain — the most common presentation; deep ache or burning behind the medial malleolus, worsened by pushing off or rising onto toes
- Triggering or clicking of the big toe — the hallmark of nodule formation; the toe catches, locks in flexion, or clicks audibly during active or passive motion
- Pain specifically with big toe extension — passively pulling the big toe up while palpating the tendon behind the ankle reproduces the pain precisely
- Medial arch pain — Zone 2 involvement; pain along the inner foot between the heel and ball, easily confused with plantar fasciitis or posterior tibial tendinopathy
- Pain worse with push-off during running — the powerful big toe push-off at toe-off phase of gait loads the FHL maximally; pain spikes at this point
- Morning stiffness — limited big toe extension first thing in the morning, easing after 10–15 minutes of walking (similar to plantar fasciitis morning pattern)
- Swelling behind the ankle — tenosynovitis produces fluid in the tendon sheath, visible and palpable as a soft swelling medial to the Achilles tendon
- Pain with ballet releve or relevé en pointe — the single most loaded position for FHL; dancers typically identify pain precisely at this moment
Causes and Risk Factors for FHL Tendinitis
FHL tendinitis is an overuse injury at its core — but specific activities and anatomical factors create disproportionate risk. Understanding why your FHL became inflamed is as important as treating the inflammation, because without addressing the cause, recurrence is nearly universal.
Ballet and dance: The highest-risk population by far. The releve position (rising onto demi-pointe or full pointe) generates extreme FHL loading, and professional dancers perform this movement hundreds of times per rehearsal. The FHL is literally referred to in dance medicine as “the Achilles tendon of the ballet dancer.” We see a significant number of dancers at Balance Foot & Ankle, and FHL tendinopathy is among the top three diagnoses in this population.
Distance running with increased mileage: The push-off phase of running loads the FHL with each stride. Rapid mileage increases — the classic “too much, too fast” pattern — exceed the tendon’s adaptive capacity. Heel strike runners who transition to midfoot or forefoot striking dramatically increase FHL demand as the toe push-off becomes more active. Trail runners descending steep grades also load the FHL heavily through repeated braking.
Gymnastics and jumping sports: Repeated floor routines, beam dismounts, and vaulting generate high-impact FHL loading. The posterior ankle fibro-osseous tunnel is compressed with each landing in plantarflexion.
Anatomical risk factors: A tight posterior ankle (limited dorsiflexion, os trigonum, posterior ankle impingement) forces the FHL to work harder for each step. Hallux valgus (bunion) alters the pull vector of the FHL, increasing tendon friction. Cavus (high arch) foot type increases FHL tension at baseline.
Footwear factors: Flat, flexible shoes with no arch support allow excessive midfoot pronation, increasing FHL strain. Transition to minimalist footwear without adequate conditioning is a common precipitating factor we see in runners who develop FHL tendinitis after switching shoe types.
How FHL Tendinitis Is Diagnosed
FHL tendinitis is primarily a clinical diagnosis — a skilled podiatric examination is more informative than imaging in most cases. The specific examination findings are highly diagnostic, and MRI is used to confirm, grade severity, and rule out associated pathology rather than to make the initial diagnosis.
Clinical examination findings: Tenderness posterior and inferior to the medial malleolus along the FHL course. Pain with resisted big toe flexion (plantarflexion of the hallux against resistance). Pain with passive big toe extension (dorsiflexion of the hallux while ankle is in plantarflexion). The “triggering test” — passively moving the ankle from plantarflexion to dorsiflexion while the big toe is kept in slight flexion — produces audible or palpable triggering in nodule-positive cases. Crepitus palpable over the tendon sheath suggests tenosynovitis.
MRI: Best imaging modality for FHL. Shows tendon thickening, mucoid signal change within the tendon, fluid in the tendon sheath (tenosynovitis), nodule location, and any associated posterior ankle impingement or os trigonum. MRI grading guides treatment decisions — mild tenosynovitis responds to conservative care, while extensive nodule formation or partial tear may indicate earlier surgical consideration.
Ultrasound: An excellent bedside tool for dynamic assessment. Real-time ultrasound can visualize the tendon as the ankle and toe move, directly demonstrating triggering of a nodule within the fibro-osseous tunnel. Ultrasound-guided injections provide both diagnostic and therapeutic value.
X-ray: Limited value for FHL tendinitis itself, but essential to rule out os trigonum (a common co-pathology), talar posterior process fracture, and hallux sesamoid pathology. An os trigonum that is compressing the FHL in the posterior ankle tunnel is a surgically correctable cause of FHL tendinopathy.
Differential Diagnosis for FHL Tendinitis
Because FHL tendinitis produces pain in the medial ankle and arch — exactly where several other conditions hurt — it is routinely misdiagnosed. The differential must be worked through systematically, and in our clinic we never treat medial ankle or arch pain without specifically testing for FHL involvement.
| Condition | Key Differentiator | Test |
|---|---|---|
| Posterior tibial tendinopathy | Pain with resisted foot inversion; PTT tender above navicular; progressive flat foot | Single heel raise test; MRI PTT |
| Tarsal tunnel syndrome | Burning/tingling in plantar foot; positive Tinel’s at tarsal tunnel; neurological | EMG/NCS; Tinel’s sign |
| Plantar fasciitis | Medial heel pain specifically; worse first step; no triggering of big toe | Windlass test; heel tenderness |
| Os trigonum syndrome | Posterior ankle pain with plantarflexion; often co-exists with FHL | Forced plantarflexion test; X-ray/MRI |
| Sesamoiditis / sesamoid fracture | Under-ball-of-foot pain; sesamoid direct tenderness; worse in thin shoes | Sesamoid X-ray; MRI |
| Posterior ankle impingement | Pain with forced plantarflexion (not dorsiflexion); often in dancers | Forced plantarflexion provocation; MRI |
Conservative Treatment for FHL Tendinitis
The majority of FHL tendinitis cases — particularly those without nodule formation or partial tear — respond very well to a structured conservative protocol. The critical factor is that treatment must be specific to FHL, not generic tendinitis management. We have seen patients spend months on plantar fasciitis protocols without improvement because the actual diagnosis was FHL tendinopathy — once the correct tendon is targeted, recovery accelerates significantly.
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Activity modification — weeks 1 to 4: Reduce or eliminate the specific activity driving the injury. Dancers should reduce or stop full pointe work. Runners should cut mileage by 50% and avoid hills and speed work. The goal is reducing FHL loading below the threshold that maintains inflammation while keeping the tendon active enough to respond to rehabilitation. Complete rest is rarely necessary and leads to deconditioning.
Eccentric toe flexion strengthening — weeks 2 to 8: The evidence base for eccentric tendon loading in tendinopathy is robust. For FHL, the exercise involves a slow, controlled extension of the big toe against resistance (resisted dorsiflexion of the hallux) held for 3 seconds, then slow release. Three sets of 15 repetitions, twice daily. This stimulates tendon collagen remodeling and progressively increases load tolerance. In our practice, we begin this protocol as soon as acute tenosynovitis has settled — typically by week 2.
Heel rise avoidance and arch support: Flat flexible shoes increase FHL tension. A slight heel rise (8-10mm) reduces the excursion required of the FHL tendon with each step. Rigid arch support further reduces midfoot pronation and FHL strain. CURREX RunPro insoles with their dynamic arch zone are the performance insole we recommend most frequently for runners with FHL tendinitis — the arch profile reduces midfoot pronation and the deep heel cup stabilizes the hindfoot, protecting the FHL along its entire course.
Corticosteroid injection — selective use: Ultrasound-guided corticosteroid injection into the FHL tendon sheath (not the tendon itself) is highly effective for acute tenosynovitis. It reduces sheath inflammation rapidly, allowing rehabilitation to begin. We use this selectively — for patients who are not improving with 4–6 weeks of conservative care, or when acute tenosynovitis is preventing any rehabilitation progress. Injection directly into the tendon body is avoided due to rupture risk.
Night splint or boot: For patients with significant morning stiffness, a soft night splint maintaining the ankle in neutral keeps the FHL at length overnight, reducing the tendon shortening that causes that sharp morning pain. This is the same principle as plantar fasciitis night splinting — the FHL runs parallel to the plantar fascia and benefits from similar sustained stretch.
Topical anti-inflammatory therapy: Doctor Hoy’s Natural Pain Relief Gel applied along the FHL tendon course — from behind the medial malleolus down through the medial arch — provides consistent topical arnica and camphor delivery that reduces peritendinous inflammation. Apply morning and evening, massaging gently along the tendon in the direction of fibers. This complements your rehabilitation program and reduces the need for oral NSAIDs.
When Surgery Is Needed for FHL Tendinitis
Surgical intervention is reserved for cases that have failed 3–6 months of comprehensive conservative treatment, or for patients with significant nodule formation causing persistent triggering (hallux saltans), partial or complete tendon tears, or co-existing os trigonum requiring excision. In our practice, the surgical threshold is higher than in some specialties — we have seen many patients whose “failed conservative care” actually failed because the conservative care was generic rather than FHL-specific. Revisiting conservative care with the correct protocol often avoids surgery.
FHL tendon sheath release and nodule excision: Through a posteromedial approach, the fibro-osseous tunnel at the posterior ankle is opened, the tendon sheath decompressed, and any nodule within the tendon is excised and the remaining tendon tubularized. This directly addresses the mechanical cause of triggering and eliminates the friction that drives ongoing inflammation. Most patients return to full activity within 3–4 months.
Os trigonum excision with FHL decompression: When an os trigonum is compressing the FHL in the posterior ankle tunnel, excision of the os trigonum provides dramatic relief for both posterior impingement symptoms and FHL tendinopathy. Endoscopic (camera-assisted) approaches allow this procedure through two small portals with faster recovery than open surgery.
⚠ Red Flags: See a Podiatrist Promptly
- Big toe that locks in a flexed position and cannot be straightened without manual assistance — nodule has become too large to pass through the fibro-osseous tunnel
- Sudden severe pain in the posterior ankle with a “pop” sensation — FHL tendon rupture until proven otherwise; requires urgent MRI
- Progressive flat foot deformity developing alongside medial ankle pain — posterior tibial tendon rupture may co-exist with FHL tendinopathy
- Numbness or tingling in the plantar foot — tarsal tunnel syndrome co-existing with FHL tenosynovitis causing nerve compression
- No improvement after 6–8 weeks of correct rehabilitation — MRI to assess for partial tear or significant nodule requiring surgical planning
Recommended Products for FHL Tendinitis
CURREX RunPro — Performance Arch Support for Runners
CURREX RunPro is the only performance insole we recommend for runners with FHL tendinitis. Available in three arch height profiles (low/medium/high), the dynamic arch zone cradles the medial longitudinal arch to reduce pronation-driven FHL strain, while the deep heel cup stabilizes the hindfoot. Available in most standard running shoe sizes. Not Ideal For: dress shoes, narrow toe-box shoes, or patients with severe custom-orthotic-dependent deformities.
Doctor Hoy’s Natural Pain Relief Gel — Tendon Inflammation Relief
Applied along the FHL tendon course from behind the medial malleolus into the arch, Doctor Hoy’s arnica and camphor formula penetrates peritendinous tissue to reduce inflammation between sessions. Massage in the direction of tendon fibers for best results. Replaces topical Biofreeze for all tendinopathy applications at our clinic. Not Ideal For: open skin, acute post-injection sites, or camphor sensitivity.
In-Office Treatment at Balance Foot & Ankle
FHL tendinitis that doesn’t respond to rest and generic stretching needs targeted intervention. Dr. Tom Biernacki provides ultrasound-guided tendon sheath injections, FHL-specific rehabilitation protocols, and when necessary, FHL tendon release and nodule excision surgery. Accurate diagnosis is the starting point — we determine which zone is affected and why before any treatment begins.
Serving dancers, runners, and athletes in Howell and Bloomfield Hills, Michigan. Same-day appointments available for acute injuries.
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Big Toe Pain or Ankle Pain That Won’t Resolve?
If your big toe clicks, catches, or your medial ankle keeps hurting despite treatment — FHL tendinitis may be the answer.
Dr. Tom Biernacki, DPM · 4.9★ · 1,123 reviews · 3,000+ surgeries
(810) 206-1402 · Howell & Bloomfield Hills, MI
What is the difference between FHL tendinitis and plantar fasciitis?
Plantar fasciitis produces pain specifically at the medial heel — the point where the plantar fascia inserts into the calcaneus. The pain is worst on the first step in the morning and eases with walking. FHL tendinitis produces pain along the inner ankle and arch, and the hallmark is pain with big toe extension (pulling the toe up) and often a clicking or triggering sensation during motion. The Windlass test (raising the big toe to stretch the fascia) is positive in plantar fasciitis; resisted big toe flexion and triggering with passive hallux motion are positive in FHL tendinitis. Both can coexist.
Can dancers continue to train with FHL tendinitis?
Modified training is usually possible in early to moderate FHL tendinitis. Full pointe work and releve should be reduced or temporarily eliminated. Floor work, barre exercises not involving releve, and conditioning that doesn’t load the FHL can continue. Complete rest is rarely necessary and causes significant deconditioning. A dance medicine specialist or podiatric surgeon familiar with dancers should guide return-to-dance timelines. In our practice, we aim to keep dancers in the studio in some capacity throughout treatment — complete breaks often cause more harm than good.
How long does FHL tendinitis take to heal?
Mild FHL tendinitis (tenosynovitis without nodule) typically resolves in 6–12 weeks with activity modification, eccentric strengthening, and arch support. Moderate tendinopathy with nodule formation may take 3–6 months. Surgery when required is followed by 3–4 months of rehabilitation before return to full sport. The single biggest factor in recovery time is whether the activity causing the injury is adequately reduced during rehabilitation — continuing to push through significant pain reliably extends recovery to a year or more.
When should I see a podiatrist for FHL tendinitis?
See a podiatrist if your medial ankle or arch pain has persisted beyond 2–4 weeks of relative rest, if your big toe is clicking or triggering, if you are a dancer or runner who cannot maintain their training despite modification, or if you have tried generic tendinitis treatments without improvement. FHL tendinitis is frequently misdiagnosed as plantar fasciitis or posterior tibial tendinopathy — an accurate diagnosis is the foundation of an effective treatment plan.
Does insurance cover FHL tendinitis treatment?
Yes. Evaluation, imaging (X-ray, MRI, ultrasound), and conservative treatment for FHL tendinitis are covered by most major insurance plans. Ultrasound-guided injections are covered under most plans with prior authorization. Surgery for tendon release or nodule excision is covered as a medically necessary procedure when conservative care has been appropriately attempted. Our office verifies your benefits before your appointment and handles all prior authorization paperwork.
Sources
- Sammarco GJ, Cooper PS. Flexor hallucis longus tendon injury in dancers and non-dancers. Foot Ankle Int. 1998;19(6):356-362.
- 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.
- Holt KL, Macera CA, Nichols JF, et al. Overuse injuries in ballet dancers: a 3-year prospective study. Am J Sports Med. 2002;30(5):701-707.
- Alfredson H. The chronic painful Achilles and patellar tendon: research on basic biology and treatment. Scand J Med Sci Sports. 2005;15(4):252-259.
- Hua Y, Yang Y, Chen S, Cai Y. Ultrasound examination for the diagnosis of chronic insertional Achilles tendinopathy and plantar fasciitis. Exp Ther Med. 2012;4(2):227-231.
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Dr. Tom Biernacki, DPM is a board-certified foot & ankle surgeon (ABFAS & ABPM) at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has made him one of the most-followed foot & ankle educators on YouTube.