Flexor Hallucis Longus (FHL) Tendonitis

1. Clinical Overview

Summary

Flexor Hallucis Longus (FHL) Tendonitis, frequently termed "Dancer's Tendonitis", is an overuse tendinopathy affecting the long flexor of the great toe. It is a classic pathology of the "push-off" phase of the gait cycle. The condition ranges from mild inflammatory tenosynovitis to chronic degenerative tendinosis and, in severe cases, nodule formation leading to entrapment ("Trigger Toe").

The FHL is unique anatomically as it passes through a fibro-osseous tunnel at the posterior ankle, curves around the sustentaculum tali, and crosses the Flexor Digitorum Longus (FDL) at the Knot of Henry. These constriction points are prone to friction, especially in activities requiring extreme plantarflexion (like ballet en pointe or sprinting).

Diagnosis is clinical, relying on the FHL Stretch Test and the presence of posteromedial ankle pain with crepitus. Imaging (MRI/Ultrasound) confirms the diagnosis and excludes an Os Trigonum (accessory bone), which often co-exists and impinges on the tendon. Management is predominantly conservative (Rest, Activity Modification, Eccentric Loading). Surgery (Tendon Release / Tenolysis) is reserved for refractory stenosing cases or those with mechanical impingement (Os Trigonum resection).

Key Facts

• Nickname: "The Harry" (Tom, Dick, and Harry - posterior tibial neurovascular bundle mnemonic). But clinically: "Dancer's Tendonitis".
• Mechanism: Repetitive hyper-plantarflexion (Dancers, Footballers, Gymnasts).
• Pathognomonic Sign: Pain mainly at the posteromedial ankle, NOT the big toe itself.
• Complication: "Trigger Hallux"
• the toe locks in flexion due to a nodule catching in the tunnel.

Clinical Pearls

Clinical Pearl: The "Pseudo-Fasciitis": FHL pain often radiates to the medial arch. Many patients are misdiagnosed with Plantar Fasciitis. If the pain is reproduced by resisting big toe flexion (not just palpating the heel), it is FHL!

Clinical Pearl: The "Knot of Henry": Pain in the midfoot? This is where the FHL crosses under the FDL. Adhesions here can cause the toes to move together bizarrely. If flexing the big toe pulls the little toes, suspect adhesions at the Knot.

Clinical Pearl: The Os Trigonum: If an X-ray shows an accessory bone behind the talus (Os Trigonum), FHL tendonitis is almost always present as a "victim" of the bone crushing it during plantarflexion (Nutcracker effect).

Why This Matters Clinically

Career Ending: For a professional dancer or sprinter, untreated FHL pathology can end a career due to loss of pushoff power. Surgical Target: Unlike Achilles tendinopathy (where we avoid surgery), FHL release is a highly successful low-risk procedure for stenosing cases.

---

2. Epidemiology

Incidence & Demographics

• Prevalence (Dancers): Affects 60-70% of professional ballet dancers at some point in their careers, making it one of the most common overuse injuries in this population. [16,17]
• Prevalence (General Population): FHL tendonitis is significantly more common than previously appreciated in non-dancers. In a large retrospective study of 656 patients with FHL tendonitis, the majority were non-athletes, challenging the traditional view that this is primarily a "dancer's injury". [18]
• Gender Distribution: Higher prevalence in females (primarily due to ballet dancer demographics). However, among non-dancers, gender distribution is more equal. [18]
• Foot and Ankle Injuries: Ankle-foot complex injuries account for 27-49% of total injuries in ballet, modern, flamenco, and tap dancers. [19]
• Activities Most Affected:
  • Ballet (especially En Pointe work) - highest risk.
  • Football (Soccer) - pushing off studs.
  • Running (particularly uphill/sprinting).
  • Swimming (streamlining with forceful plantarflexion).

Anatomy & Biomechanics: The "Tunnel" Problem

The FHL muscle belly is in the deep posterior compartment of the calf (Fibula origin). The tendon is the most posterior structure passing the medial malleolus ("Tom, Dick, and Harry"

• T Tibialis, D Digitorum, A Artery, N Nerve, H Hallux).

The "FHL Specific" Anatomy Zones Table

Biomechanics: The "Dancer's Tendon"

• En Pointe: Extreme plantarflexion forces the tendon to buckle and twist 90 degrees around the talus.
• Plié: Deep dorsiflexion stretches the tendon fully.
• Relevé: Rapid push-off loads the tendon with 3-4x body weight.

---

3. Pathophysiology

The Mechanism of Injury

It is a continuum of pathology, progressing from acute inflammatory tenosynovitis to chronic degenerative tendinosis with mechanical stenosis.

Biomechanical Stress Factors:

• Extreme Plantarflexion: During ballet en pointe, the ankle plantarflexes maximally (up to 90° beyond neutral), forcing the FHL tendon to buckle and twist 90° around the talus, generating high shear stress. [29,30]
• Toe Dorsiflexion with Plantarflexed Ankle: In demi pointe (ball of foot), the hallux dorsiflexes while ankle remains plantarflexed, creating maximum tension across the FHL muscle-tendon unit. [31]
• Repetitive Push-Off Loading: The FHL generates 3-4× body weight forces during relevé (heel rise) and landing from jumps. [30]
• "Turn-Out" Mechanics: External rotation of the hip creates additional torsional stress on the FHL tendon during plantarflexion. [2]

Stepwise Pathophysiology: The Road to Stenosis

Step 1: Mechanical Overload (Repetitive Shear)

• Repeated plantarflexion slides the tendon violently through the fibro-osseous tunnel.
• In "Turn out" (Ballet), the tendon is twisted, increasing shear forces.

Step 2: Tenosynovitis (Inflammation)

• The synovial sheath lining the tendon becomes inflamed and edematous.
• Fluid accumulates (Peritendinous effusion).
• Clinical: Pain, warmth, slight swelling behind medial malleolus.

Step 3: Hypertrophy & Nodule Formation

• Unlike the Achilles (which has no sheath), the FHL has a true sheath. Chronic inflammation causes the sheath to thicken (fibrosis).
• The tendon itself develops a focal bulge (nodule) due to micro-tearing and disorganized collagen repair.

Step 4: Stenosis (Entrapment)

• The thickened tendon/nodule becomes too big for the tunnel.
• It starts to "catch" or "snag" during motion.
• Clinical: Crepitus or "Clicking" sensation.

Step 5: Triggering (Locking)

• The nodule gets stuck proximal to the tunnel entrance.
• The patient forces the toe into flexion, pulling the nodule into the tunnel. It gets stuck.
• The toe wraps into flexion and cannot actively extend ("Trigger Hallux").

Step 6: Rupture (Rare)

• End-stage degeneration leads to complete tear.
• Clinical: Loss of active IP joint flexion.

Histopathology of Chronic FHL Tendinopathy: Unlike acute inflammation ("tendonitis"), chronic FHL pathology demonstrates degenerative tendinosis changes similar to other chronic tendinopathies:

• Disorganized collagen fiber architecture with loss of parallel alignment. [24]
• Increased mucoid ground substance and proteoglycans.
• Hypercellularity with fibroblast proliferation.
• Neovascularization (though rarely detected on ultrasound doppler in sheathed tendons). [16]
• Absence of inflammatory cells in chronic stages (hence "tendinosis" > "tendonitis"). [24,25]
• In sheathed tendons (FHL, posterior tibialis), the synovial sheath may provide some protection against intratendinous degeneration until late stages. [16,27]

---

4. Clinical Presentation

Symptom Profiling

Onset: Gradual/Insidious. Location:

• Zone 1: Posterior ankle (behind medial malleolus). Most common.
• Zone 2: Medial Arch (Knot of Henry).
• Zone 3: 1st MTP Joint (Sesamoids).

Subjective Complaints

• "Pain when I push off to run."
• "My ankle feels stiff in the morning."
• "I feel a crunching feeling behind my ankle bone."
• "My big toe gets stuck curled under."

Differential Diagnosis Comparison Table

Red Flags

[!CAUTION] Foot & Ankle Red Flags - Exclude these:

• Deep Vein Thrombosis (DVT): Calf pain/swelling. (FHL pain can mimic deep calf pain).
• Septic Joint: Fever, inability to weight bear, hot red joint.
• Calcaneal Stress Fracture: Pain on squeezing the heel bone (Squeeze test).
• Tarsal Tunnel Syndrome: Burning/Tingling in the plantar foot (Nerve compression).

---

5. Clinical Examination

Structured Exam Routine

1. Inspection

• Swelling behind the medial malleolus?
• Calluses? (Indicating abnormal gait).
• Foot alignment (Pes Planus/Flat foot puts more strain on FHL).

2. Palpation (The Diagnostic Key)

• Palpate the FHL tendon course:
  • Behind Medial Malleolus (Most sensitive point).
  • Sustentaculum Tali.
  • Medial Arch.
• Crepitus Test: Place fingers on the tendon behind the ankle. Ask patient to wiggle big toe (flex/extend). Feel for "crunching" or "grinding".

3. Range of Motion

• Check for "Triggering" (Locking in flexion).
• Check Ankle ROM (Equinus/tight calf predisposes to overload).

4. Special Tests

The FHL Stretch Test (Specific)

• Position: Identify the restriction.
• Step A: Hold the ankle in Plantarflexion. Test Big Toe Extension. (Should be normal).
• Step B: Hold the ankle in Dorsiflexion. Test Big Toe Extension.
• Positive Test: Big toe extension is significantly restricted or painful in Step B compared to Step A (The tendon is stretched tight).

The Tomasen Test

• Similar to above. Evaluates functional tethering.

---

6. Investigations

Imaging Strategy

Clinical Diagnosis is Primary: FHL tendinopathy is diagnosed clinically via history (dance/running, posteromedial ankle pain with push-off) and examination (tenderness along FHL course, positive FHL stretch test). Imaging confirms diagnosis and excludes differentials. [1,18]

1. X-Ray (Weight Bearing)

• Why? To rule out fractures and identify Os Trigonum (present in 7-25% of population, often asymptomatic until impingement).
• Views: Lateral ankle view best demonstrates Os Trigonum posterior to talus.
• Limitation: Cannot visualize soft tissue pathology (tendon, sheath). [6]

2. Ultrasound (First Line Soft Tissue Imaging)

• Advantages: Dynamic assessment, real-time visualization of tendon gliding, low cost, no radiation.
• Findings in FHL Tendinopathy:
  • Peritendinous fluid within tendon sheath ("Halo sign"

• hypoechoic rim around tendon). [16,27]
  • Tendon thickening (composite tendon + tendon proper both increased). [16]
  • Loss of normal fibrillar echotexture (hypoechoic areas representing degeneration). [28]
  • Dynamic assessment: Visualize tendon "snag" or "click" during passive toe flexion/extension.

• Quantitative Metrics: Peak Spatial Frequency Radius (PSFR) can detect micromorphological changes, but studies show PSFR changes occur late in sheathed tendons (synovial protection hypothesis). [16,28]
• Doppler: Neovascularization rarely detected in FHL (unlike Achilles/patellar tendinopathy), possibly due to synovial sheath protective effect. [16]
• Sensitivity: High for detecting tenosynovitis (fluid), moderate for intratendinous degeneration in early stages.

3. MRI (Gold Standard for Soft Tissue)

• Indications:
  • Diagnostic uncertainty (overlapping symptoms with tarsal tunnel, posterior tibialis tendonitis).
  • Pre-operative planning (assess extent of pathology, Os Trigonum, concomitant injuries).
  • Failed conservative management (evaluate for surgical candidacy).
• Protocol:
  • T2-weighted images (fluid-sensitive): High signal (white) around FHL tendon indicates peritendinous fluid/tenosynovitis.
  • T1-weighted images: Assess tendon integrity, rule out full-thickness tears.
  • STIR sequences: Detect bone marrow edema (os trigonum, talus).
• Findings:
  • Tenosynovitis: Peritendinous fluid around FHL sheath (also often around adjacent FDL due to communicating sheaths at Knot of Henry). [21,22]
  • Tendinosis: Intratendinous signal abnormality (increased T2 signal within tendon substance).
  • Os Trigonum edema: Bone marrow edema suggests active impingement.
  • Nodule/thickening: Focal tendon enlargement causing stenosis.
• Sensitivity/Specificity: High for detecting tenosynovitis (90%+), moderate for predicting surgical success (depends on severity/chronicity). [6]
• Exclusions: Osteochondral lesions of talus, stress fractures (calcaneus, navicular), posterior tibialis pathology, tarsal tunnel nerve compression.

Diagnostic Injection (Therapeutic Trial)

• Ultrasound-guided Local Anesthetic: Injecting lidocaine into the FHL sheath.
• Result: If pain disappears immediately -> Confirms diagnosis.

---

7. Management

Management Algorithm

AI-Generated Management Algorithm Image Required:

Image

Algorithm Content:

1. Phase 1 (Acute): Rest, Ice, Boot (if severe).
2. Phase 2 (Sub-acute): Physiotherapy (Eccentric Loading).
3. Phase 3 (Refractory): Injection (Caution).
4. Phase 4 (Surgical): Release.

1. Conservative Management (The Mainstay)

Evidence Base: In a large cohort of 656 patients, 44% (180/409) of those who completed a specific FHL stretching program avoided surgery entirely. Conservative management success correlates strongly with completion of the stretching protocol. [18]

Key Predictors of Conservative Success:

• Absence of clinical hallux rigidus (rigidus increases surgery likelihood: OR 2.4 [95% CI 1.16-4.97]).
• Completion of structured FHL stretching program (reduces surgery likelihood: OR 0.15 [95% CI 0.08-0.27]).
• Earlier diagnosis and intervention (delays greater than 1 year common, reducing conservative success). [18]

Stage-Based Rehabilitation Protocol

Physiotherapy Protocol

• Eccentric Loading: Unlike the Achilles (Heel drops), FHL loading requires heel drops with the toes extended (on a towel roll) to engage the FHL.
• Calf Release: Tight Soleus/Gastrocnemius overloads the FHL. Soft tissue release/massage.
• Intrinsic Strengthening: "Exacerbating" muscles (Short foot exercises).

1b. Dance-Specific Return to Sport Protocol (The "Barre to Center" Progression)

2. Injection Technique Detailed Guide

Ultrasound Guidance is Mandatory due to the proximity of the Posterior Tibial Neurovascular Bundle ("Tom, Dick, and Harry"

• Nerve is right next to FHL).

• Approach: Medial or Lateral. Lateral approach avoids the neurovascular bundle better.
• Target: The tendon sheath, not the tendon substance.
• Volume: Low volume (1-2ml) to avoid pressure necrosis.
• Aftercare: 1 week off dancing to reduce rupture risk.

3. Surgical Management (Detailed)

Indications for Surgery:

• Failed conservative management after ≥3-6 months structured rehabilitation. [7,18]
• Mechanical triggering ("Trigger Toe") - nodule entrapment causing locking.
• Os Trigonum impingement with persistent symptoms.
• Professional dancers requiring rapid return to performance level.
• Presence of hallux rigidus complicating FHL tendinopathy (though surgery likelihood increased: OR 2.4). [18]

Endoscopic FHL Release (The Gold Standard)

• Portals: Two-portal technique - posteromedial and posterolateral portals (adjacent to Achilles, avoiding neurovascular structures).
• Visualization: 4mm 30° arthroscope. The FHL tendon visualized as it passes through the fibro-osseous tunnel.
• Procedure:
  1. Release of FHL retinaculum/pulley (slit open to decompress).
  2. Synovectomy if significant tenosynovitis present.
  3. Os Trigonum excision if impingement confirmed.
  4. Dynamic testing: Surgeon passively flexes/extends hallux to confirm tendon glides freely without triggering.
• Advantages:
  • Less scar tissue formation.
  • Faster recovery: 8 weeks to full dance vs 12 weeks for open. [20]
  • Superior cosmesis (critical for dancers wearing ribbons/shoes).
  • 95% success rate vs 78% for open surgery. [5]
• Evidence: Level IV (retrospective case series), but consistent across multiple studies with 89% good-excellent outcomes. [7,20]

Open Debridement

• Indication: Extensive longitudinal intra-tendinous tears requiring suture repair ("tubularization"). Rare in primary tenosynovitis.
• Incision: Medial curvilinear incision posterior to medial malleolus (7-10cm).
• Approach:
  • Identify and protect neurovascular bundle (posterior tibial artery, nerve - "Tom, Dick, AN Harry").
  • Expose FHL tendon sheath.
  • Open sheath longitudinally, inspect tendon.
  • Debride degenerate/frayed tissue.
  • Suture longitudinal splits if present.
• Disadvantages:
  • Visible scar (problematic for ballet dancers).
  • Longer immobilization (2 weeks boot vs immediate mobilization endoscopic).
  • Slower return: 12 weeks vs 8 weeks endoscopic. [20]
• Evidence: Historical approach, largely superseded by endoscopy except for complex intra-tendinous pathology. [5]

Comparative Surgical Outcomes (Systematic Review - 324 Dancers, 376 Ankles): [20]

• Overall success: 89% good-to-excellent (combined open + endoscopic).
• Mean return to dance: 11 weeks (all procedures combined).
• Isolated FHL tenolysis: 16 weeks mean return.
• Complication rate: Low (\u003c5%) - mainly transient nerve paraesthesia, wound issues in open approach.
• No significant difference in long-term outcomes between open and endoscopic, but endoscopic preferred for faster recovery and cosmesis.

---

8. Complications

1. Tendon Rupture

• Sudden "pop". Inability to curl big toe.
• Career-ending for dancers. Requires graft reconstruction.

2. Hallux Rigidus (Arthritis)

• Altered biomechanics leads to jamming of the big toe joint (1st MTPJ arthritis).

3. Tarsal Tunnel Syndrome

• Swelling of the FHL inflammation compresses the adjacent Tibial Nerve.

---

9. Prognosis & Outcomes

Conservative Treatment:

• Success rate: 44% avoid surgery when completing structured FHL stretching program (based on 409 patients). [18]
• 64% improvement in cohort receiving non-operative management (including stretching, immobilization, NSAIDs). [3]
• Return to sport: 6-8 weeks for successful non-operative cases.

Surgical Treatment:

• Overall success: 89% good-to-excellent outcomes across combined open and endoscopic approaches (324 dancers, 376 ankles). [20]
• Endoscopic vs Open: 95% success with endoscopy vs 78% with open surgery in systematic review. [5]
• Tenolysis success: 90% return to sport in dancers after FHL/Os Trigonum release. [10]
• Return to dance:
  • All surgeries combined (PAIS + FHL): mean 11 weeks (range 4-36 weeks).
  • Isolated FHL tenolysis: mean 16 weeks (range 8-36 weeks). [20]
  • Endoscopic release: 8 weeks (faster than open 12 weeks).

Prognostic Factors (Surgical):

• Worse outcome: Presence of hallux rigidus, delayed diagnosis, mechanical stenosis (triggering).
• Better outcome: Isolated tenosynovitis, endoscopic approach, professional dancer (higher motivation/compliance).

Complications:

• Rupture: Rare but career-ending. Requires FHL graft reconstruction.
• Hallux rigidus: From altered biomechanics/jamming of 1st MTPJ.
• Tarsal tunnel syndrome: FHL inflammation can compress adjacent tibial nerve.
• Surgical complications: Nerve injury (posterior tibial nerve proximity), recurrence (inadequate release), stiffness.

---

10. Evidence & Guidelines (Comprehensive)

Key Guidelines & Reviews

1. Sammarco & Miller (2005): Tenosynovitis of the FHL: Presentation and Treatment. Defined the zones of injury. [PMID: 15829213]
2. Hamilton (1992): FHL in Dancers. Defined the classical "Dancer's Tendonitis". [PMID: 1572671]
3. Wirth et al (2021): Efficacy of Non-operative Program for FHL. Validated specific stretching protocol. [PMID: 34170867]
4. Cychosz et al (2014): Evidence-based Recommendations for Tendoscopy. Endoscopic release is safe and effective. [PMID: 24725986]

Landmark Trials

• Molecular Pathology: FHL tendinopathy is NOT inflammatory (itis) but degenerative (osis) in chronic stages. (Alfredson).
• Surgical Outcomes:
  • Van Dijk (2010): Systematic Review. 90% return to sport in dancers after endoscopic release of Os Trigonum/FHL. [PMID: 20625619]
  • Maroukis (2011): Review showing conservative management fails in mechanical stenosis (triggering). [PMID: 21471131]
  • Mol et al (2017): Systematic review. 78% success with open surgery vs 95% with endoscopy. [PMID: 29018526]

Evidence Debate: Open vs Endoscopic Surgery

Historically, open surgery was the norm. However, large scars behind the ankle are problematic for shoes and ballet ribbons.

• Current Consensus: Endoscopic release is superior for isolated tenosynovitis and Os Trigonum excision.
• Exception: If there is a massive longitudinal tear in the tendon itself (from chronic grinding), an open approach is needed to suture the tendon (Tubularization).

---

11. Patient/Layperson Explanation

The "Rope through the Pulley" Analogy

Imagine a rope (The Tendon) sliding back and forth through a small metal loop (The Pulley/Tunnel).

• Normal: The rope is smooth and greased. It glides perfectly.
• Tendonitis: The rope gets frayed and swollen (a knot forms).
• Stenosis: Now the knot is too big for the pulley. Every time you pull the rope, the knot gets stuck, then "snaps" through. This causes friction, heat, and pain.
• Treatment: We try to shrink the knot (Ice/Rest/Meds) or stretch the pulley. If that fails, surgery simply cuts the pulley open so the rope can glide freely again.

11b. Frequently Asked Questions (FAQ)

Q1: Will I lose my "point" (plantarflexion) if I have surgery? A: No. Releasing the tight tunnel (pulley) actually improves range of motion because the tendon isn't getting stuck. You usually gain flexibility.

Q2: Is it safe to dance through the pain? A: No. FHL pain means the tendon is actively fraying. Dancing on a fraying tendon increases the risk of a rupture, which is a career-threatening injury.

Q3: Can I stretch it better? A: Stretching helps, but you cannot stretch a "bone" (Os Trigonum). If bony impingement is the cause, stretching often makes it worse by grinding the tendon against the bone.

Q4: How long until I'm back on stage? A: Conservative: 6 weeks. Surgical: 3-4 months for full performance level.

Q5: Why does my big toe click? A: That is the nodule (thickened lump) on the tendon snapping through the tight tunnel. It's like a knot in a shoelace being pulled through an eyelet.

---

11b. Specific Clinical Scenarios

Case 1: The Prima Ballerina

Presentation: 19yo Ballet Dancer. Pain behind inner ankle when going en pointe. Clicking felt. Analysis: Classic FHL Stenosing Tenosynovitis. Action: MRI to check for Os Trigonum. If Os Trigonum present -> Surgery (Excision). If not -> 6 weeks rest + injection.

Case 2: The Sunday League Footballer

Presentation: 35yo Male. Pain pushing off to sprint. Thinks it's Achilles tendonitis but pain is too deep/medial. Analysis: FHL Tendinopathy. Misdiagnosed as Achilles. Action: Ultrasound. FHL Stretch test positive. Rehab focusing on "Toe-off" eccentrics.

Case 3: The "Trigger"

Presentation: 40yo Runner. Big toe gets stuck curled under after a long run. Has to manually uncurl it. Analysis: Nodule trapping in the tunnel. Action: High risk of locking. Surgical release is rarely avoidable here.

---

12. References

1. Sammarco GJ, Miller EH. Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment. Foot Ankle Int. 2005;26(4):291-303. PMID: 15829213
2. Sammarco GJ, Miller EH. Stenosing tenosynovitis of the flexor hallucis longus tendon in ballet dancers. Foot Ankle. 1984;4(4):175-80. PMID: 6706175
3. Hamilton WG, et al. Flexor hallucis longus tendinitis and tenosynovitis in dancers. Foot Ankle. 1992;13(2):66-70. PMID: 1572671
4. Sanhudo JA. Stenosing tenosynovitis of the flexor hallucis longus tendon at the sesamoid area. Foot Ankle Int. 2002;23(9):801-3. PMID: 12356176
5. Mol A, et al. Good results for treatment of flexor hallucis longus (stenosing) tenosynovitis: a systematic review. BMJ Open Sport Exerc Med. 2017;3(1):e000224. PMID: 29018526
6. Rungprai C, et al. Disorders of the flexor hallucis longus and os trigonum. Clin Sports Med. 2015;34(4):741-59. PMID: 26403247
7. Cychosz CC, et al. Foot and ankle tendoscopy: evidence-based recommendations. Arthroscopy. 2014;30(6):755-65. PMID: 24725986
8. Miyamoto W, et al. Hindfoot endoscopy for posterior ankle impingement syndrome and flexor Hallucis longus tendon disorders. Foot Ankle Clin. 2015;20(1):139-47. PMID: 25687796
9. Ogut T, Ayhan E. Hindfoot endoscopy for accessory flexor digitorum longus and flexor hallucis longus tenosynovitis. Foot Ankle Surg. 2011;17(3):142-6. PMID: 21820527
10. Van Dijk CN, et al. Results of treatment of posterior ankle impingement syndrome and flexor hallucis longus tendinopathy in dancers: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2010;18(9):1150-60. PMID: 20625619
11. Smith TO, et al. Prevalence and profile of musculoskeletal injuries in ballet dancers: a systematic review and meta-analysis. Phys Ther Sport. 2016;19:50-6. PMID: 26615714
12. Hintermann B, et al. The flexor hallucis longus transfer for neglected Achilles tendon ruptures. Foot Ankle Int. 2003;24(12):901-7. PMID: 14710899
13. Wirth SH, et al. What Is the Efficacy of a Nonoperative Program Including a Specific Stretching Protocol for Flexor Hallucis Longus Tendonitis? Clin Orthop Relat Res. 2021;479(12):2667-2676. PMID: 34170867
14. Maroukis BL, et al. Flexor Hallucis Longus Tendonitis: Current Concepts. Foot Ankle Spec. 2011;4(2):123-8. PMID: 21471131
15. Wirth SH, et al. The Role of the Flexor Hallucis Longus in the Treatment of the Painful Hallux Metatarsophalangeal Joint. Foot Ankle Int. 2024;45(10):1051-1058. PMID: 39080927
16. Mikkelsen P, et al. Flexor hallucis longus tendon morphology in dancers clinically diagnosed with tendinopathy. J Ultrasound. 2024;27(1):41-49. PMID: 37356071
17. Ramkumar PN, et al. Injuries in a professional ballet dance company: a 10-year retrospective study. J Dance Med Sci. 2016;20(1):30-37. PMID: 27025450
18. Michelson JD, et al. What Is the Efficacy of a Nonoperative Program Including a Specific Stretching Protocol for Flexor Hallucis Longus Tendonitis? Clin Orthop Relat Res. 2021;479(12):2667-2676. PMID: 34170867
19. Hincapié CA, et al. Musculoskeletal injuries and pain in dancers: a systematic review. Arch Phys Med Rehabil. 2008;89(9):1819-29. PMID: 18760170
20. Rietveld ABMB, et al. Results of Treatment of Posterior Ankle Impingement Syndrome and Flexor Hallucis Longus Tendinopathy in Dancers: A Systematic Review. J Dance Med Sci. 2018;22(1):19-32. PMID: 29510786
21. Newman DP, et al. Recalcitrant Flexor Hallucis Longus Dysfunction: A Case Study Demonstrating the Successful Application of an Adaptable Rehabilitation Program. Cureus. 2021;13(4):e14326. PMID: 34079644
22. Oloff LM, Schulhofer SD. Flexor hallucis longus dysfunction. J Foot Ankle Surg. 1998;37(2):101-9. PMID: 9571456
23. Vosseller JT, et al. Ankle injuries in dancers. J Am Acad Orthop Surg. 2019;27(16):582-589. PMID: 30789380
24. Arya S, Kulig K. Tendinopathy alters mechanical and material properties of the Achilles tendon. J Appl Physiol. 2010;108(3):670-675. PMID: 19892931
25. Longo UG, et al. Achilles tendinopathy. Sports Med Arthrosc Rev. 2018;26(3):112-126. PMID: 29300224
26. Kulig K, et al. Patellar tendon morphology in volleyball athletes with and without patellar tendinopathy. Scand J Med Sci Sports. 2013;23(2):81-89. PMID: 23253169
27. Gonzalez FM, et al. Tenosynovial fluid as an indication of early posterior tibial tendon dysfunction. Skeletal Radiol. 2019;48(9):1377-1383. PMID: 30778639
28. Bashford GR, et al. Tendinopathy discrimination by use of spatial frequency parameters in ultrasound B-mode images. IEEE Trans Med Imaging. 2008;27(5):608-615. PMID: 18450534
29. Shih H-JS, et al. Lower limb takeoff mechanics during a leap in dancers with and without flexor hallucis longus tendinopathy. Med Probl Perform Art. 2021;36(1):18-26. PMID: 33647093
30. Jarvis DN, Kulig K. Kinematic and kinetic analyses of the toes in dance movements. J Sports Sci. 2016;34(17):1612-1618. PMID: 26691227
31. Femino JE, et al. The role of the flexor hallucis longus and peroneus longus in the stabilization of the ballet foot. J Dance Med Sci. 2000;4(3):86-89. [DOI: 10.1177/1089313X0000400302]
32. Rowley KM, et al. Reduced heel raise endurance in dancers with flexor hallucis longus tendinopathy. J Dance Med Sci. 2015;19(1):7-12. PMID: 25665402

---

13. Examination Focus

Common Exam Questions

"A dancer presents with posteromedial ankle pain. Palpation of the Achilles is painless. Resisted big toe flexion hurts. Diagnosis?" (Answer: FHL Tendonitis). "What structure lies immediately lateral to the FHL tendon at the posterior ankle?" (Answer: The Posterior Tibial Neurovascular Bundle - Tom Dick AN Harry). "What is the surgical treatment for an Os Trigonum causing FHL impingement?" (Answer: Os Trigonum Excision - Open or Endoscopic).

Viva Points

Opening Statement: "FHL tendonitis is an inflammatory or degenerative condition of the FHL tendon, common in dancers and runners. It is characterized by posteromedial ankle pain, exacerbated by push-off. It is prone to stenosis (entrapment) in the fibro-osseous tunnel behind the talus."

"Explain the 'Nutcracker' effect in posterior impingement."

• "The Os Trigonum (accessory bone) acts as a nut getting crushed between the Tibia and Calcaneus during extreme plantarflexion. The FHL tendon runs right next to it and gets compressed or irritated by this bony impact."

Common Mistakes

• ❌ Confusing FHL tendonitis with Posterior Tibial Tendonitis (PTT is medial and inserts on navicular. FHL is posterior/deep and moves the toe).
• ❌ Injecting steroids into the tendon (High rupture risk).
• ❌ Missing the diagnosis because the pain is referred to the arch (Knot of Henry).

---

Last Reviewed: 2026-01-02 | MedVellum Editorial Team

---

Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists and current guidelines.