Jump to content
We need you! See something you could improve? Make an edit and help improve WikSM for everyone.

Flexor Hallucis Longus Tendinopathy

From WikiSM

Other Names

  • FHL Tendonitis
  • FHL Tendinopathy
  • Flexor Hallucis Longus Tendinopathy
  • FHL Rupture
  • FHL Tenosynovitis
  • FHL Laceration
  • Dancer's Tendonitis
  • Stenosing tenosynovitis of the Flexor Hallucis Longus
  • Intersection Syndrome Foot
  • Intersection Syndrome of the Foot
  • FHL Dysfunction

Background

  • This page refers to injuries to the Flexor Hallucis Longus (FHL) tendon
    • Although generally an overuse syndrome, this page includes tendon ruptures, lacerations and other tendinopathies

History

  • Gould described the first case of stenosing tenosynovitis of the Flexor Hallucis Longus (FHL) tendon in 1981[1]

Epidemiology

  • Rare and poorly described in the literature

Introduction

Flexor Hallucis Longus is seen running through the Tarsal Tunnel
Running of the flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendons and the knot of Henry, the site where the two cross. Three zones of the FHL tendon are shown.[2]
Anatomy of Flexor Hallucis Longus[3]
Knot of Henry: 1a shows the distance of MKH to medial malleolus (MM), navicular tuberosity (NT) and first interphalangeal joint (IP). 1b shows the distance of FDL tendon division (FDLd) to lateral border of the foot (LB), medial border of the foot (MB), base of the second toe (SB) and back of the heel (HB).[4]

General

  • Flexor hallucis longus (FHL) tendinopathies represent a spectrum of disease increasingly recognized[5]
  • Patients typically present with posteromedial ankle pain with tenderness along the FHL tendon
  • MRI and Ultrasound can help confirm the diagnosis
  • Treatment is often conservative including physical therapy, activity modification and immobilization[6]

Intersection Syndrome Foot

  • Overall, poorly understood
  • Characterized by fibrosis of the intersection between the FHL and the FDL tendons at the Knot of Henry
  • Potential causes
    • Acute or chronic repetitive hyperextension of the 1st metatarsophalangeal joint
    • Partial tear of the FHL tendon at the knot

FHL Rupture/ Laceration

  • Very rare condition limited to case reports[7]
  • Can occur through traumatic laceration, closed traumatic rupture, or atraumatic mechanisms
  • Locations: metatarsal head and neck junction, plantar aspect of the first phalangeal head, knot of Henry, the groove of the talus, under the sustentaculum tali[8]
  • Patients present with sudden severe pain, weakness, and loss of great toe flexion
  • Diagnosis can be confirmed by MRI
  • Surgical repair is recommended for complete ruptures with generally favorable outcomes

Stenosing Tenosynovitis

  • Results from chronic inflammation and mechanical irritation of the tendon within its fibro-osseous tunnel
    • Most commonly at the posterior ankle where the tendon passes beneath the sustentaculum tali[9]
  • It develops through repetitive microtrauma and friction between the tendon and its surrounding sheath
  • The mechanical demands that precipitate this condition involve repetitive forefoot push-off in extreme plantarflexion[10]
    • This places supraphysiologic loads on the FHL
    • For example, en pointe position in ballet dancers exemplifies this mechanism
  • Less common locations of stenosing tenosynovitis: sesamoid area or proximal to medial malleolus[11]

Mechanism

  • Overuse/ Tendinosis
    • Activities involving maximal plantarflexion, sports requiring repetitive forefoot push-off
  • In dancers/ ballet
    • Provoked by the recurrent movement caused by changing position from a plié position to a relevé position
      • Plié is a French term meaning to bend, relevé, is a ballet term meaning “raised.”[12]
      • The term relevé explains the action when a dancer rises up on their toes
    • Loaded hyperplantarflexed positioning of the ankle experienced in ballet (particularly en pointe)
    • Can cause direct compression of the FHL through kinking of the tendon where it enters the fibro-osseous tunnel posterior to the talus
  • FHL Laceration
    • Acute laceration

Etiology

  • Fibro-osseous tunnel in tenosynovitis
    • Tends to occur in the fibro-osseous tunnel
    • Hypothesis 1[1]
      • Relative incongruity between the FHL and the fibro-osseous tunnel when the foot is in full plantarflexion
      • Could lead to abnormal stresses on the tendon when it is under extreme tension such as dancing on en pointe
    • Hypothesis 2
      • Distal excursion of the tendon during ankle and hallux dorsiflexion
      • Low-lying muscle belly just proximal to the fibro-osseous tunnel
      • As the FHL moves distally into the fibro-osseous tunnel, the muscle mass gets jammed into the tunnel, leading to inflammation or swelling

Associated Conditions

Anatomy of Flexor Hallucis Longus

Anatomy of Knot of Henry

Risk Factors

Intrinsic Risk factors for tendinopathies

  • Age-related changes (decreased healing response, decreased vascularity, increased tendon stiffness)
  • Anatomic factors (muscle imbalance, inflexibility, malalignment, muscle weakness)
  • Systemic conditions: diabetes mellitus, gout, hypertension, obesity, and smoking
  • Sports (classic)
    • Dancers[15]
    • Gymnasts
  • Sports (case reports)
    • Soccer referee[16]
    • Long distance runner[17]
  • Biomechanical
    • Excessive plantarflexion

Differential Diagnosis

Differential Diagnosis Ankle Pain

Differential Diagnosis Foot Pain

Clinical Features

Pain most commonly occurs behind the posteromedial ankle (orange)
Flexor Hallucis Longus Stretch Test[18]

History

  • Pain location and character are the primary preenting features
  • In overuse tendinopathies, the onset of symptoms is insidious
  • Patients often report posteromedial ankle and, much less commonly, great toe pain
    • Though pain can manifest anywhere along the tendon's course (plantar heel, plantar midfoot, multiple locations)
    • Pain is greatest while performing a plie position, during which the FHL tendon is stretched
  • Sports frequently implicated: ballet dancers and athletes who perform repetitive forefoot push-off in extreme plantarflexion
    • Also frequently occurs in nonathletic, middle-aged individuals
  • Great toe locking with active range of motion
  • Crepitus along the posterior medial ankle
  • Symptoms are often prolong with duration of 20 months reported in some case series[19]

Physical Exam: Physical Exam Foot

  • Tenderness to direct palpation over the musculotendinous junction of the FHL
    • Tenderness to palpation anywhere along the FHL tendon is the hallmark finding
    • Most frequent site of tenderness is at the fibro-osseous tunnel posterior to the medial malleolus[20]
  • Pain with resisted flexion of the hallux IP joint[21]
  • Pain with forced plantarflexion of the ankle
  • Great toe 'triggers' with active or passive motion (no tenderness at the level of the 1st metatarsal head)
  • Pseudo Hallux Rigidus may be present, demonstrated by limitation of great toe dorsiflexion with knee extended, ankle dorsiflexed
  • Great toe crepitus and passive dorsiflexion stiffness
  • Decreased heel elevation during bilateral heel raise

Special Tests

  • Tomasen Test: Assess 1st MTP motion in maximal plantarflexion with moderate ankle dorsiflexion
    • Approximately 37% of patients in one series demonstrated this positive finding[22]
  • Flexor Hallucis Longus Stretch Test: evaluate FHL in plantarflexion and dorsiflexion

Evaluation

Retrotalar pulley. Normal appearance and stress test. A Computed tomography 3D schematic drawings of the retrotalar pulley and the normal flexor hallucis longus (FHL). B Transverse sonogram obtained at rest, at the passage of the FHL at the medial (MT) and lateral (LT) tubercles of the talus. Note the normal retrotalar pulley (open arrowheads). C Photograph of the dynamic stress applied to the retrotalar pulley. The ankle was in slight dorsiflexion. The hallux of the patient was flexed (green arrow) against the resistance of the hand of the examiner (yellow arrow). D Transverse sonogram obtained during the stress test. The normally attached retrotalar pulley restrain the FHL (gray dashed curved arrow) to anterior luxation. Art indicates the tibial artery; lpn, lateral plantar nerve; mpn, medial plantar nerve[23]

Radiology

MRI

  • Primary imaging modality for diagnosing FHL tendinopathies
    • In one study, 28/34 patients had MRI findings confirming the clinical exam[24]
  • Findings of FHL tendinopathy
    • Fluid around tendon (tenosynovitis) of the tendon sheath at the level of the ankle
    • Intrasubstance tendinous signal
    • In laceration, tendon ends may be retracted
    • Focal tendon thickening or nodules
    • Stenosis at the fibro-osseous tunnel
    • Peritendinous edema
  • Potential findings of 'Intersection Syndrome'
    • Peritendinous edema and fluid around the flexor hallucis longus at the level of the navicular and medial cuneiform (location of knot of henry)
    • Peritendinous edema and fluid involving the flexor hallucis longus (FHL) and flexor digitorum longus (FDL)

Ultrasound

  • Advantages of ultrasound
    • Dynamic assessment, lower cost, and point-of-care availability
    • Dynamic ultrasound allows real time testing of FHL tendon through range of motion
  • Normal: compact linear band with fine internal fibrillar pattern[25]
  • Potential Findings[26]
    • Tenosynovitis with hypoechoic or anechoic fluid around the tendon
    • Tendon thickening and altered echogenicity
    • Fibrous bands adjacent to the tendon
    • Dynamic triggering or snapping during active hallux flexion and extension
    • Viscous, ganglion-like fluid that resists compression

Classification

  • Not applicable

Management

Ankle balance exercises can be used in FHL Tendinopathy

Prevention

  • Preventative conditioning is important for dancers
  • Important to maintain conditioning during breaks, layoffs
  • Strength, flexibility and proprioception
  • Well fitting shoes when appropriate[27]
  • Use of floors with good resiliency and friction characteristics
  • Proper biomechanics

Nonoperative

  • Indications
    • First line in nearly all cases
  • Initial Management[28]
    • Specific FHL stretching protocol combined with activity modification
    • Allows approximately 44% of patients to avoid surgery
  • Activity modification
    • Avoid provoking activities until symptoms are resolved
    • Reduce or eliminate activities involving repetitive forefoot push-off in extreme plantarflexion
    • Correct training errors, and address footwear issues including worn-out athletic shoes or high heels
  • Correcting biomechanics (Dancers)
    • Reduce turnout of the hip so the dancer is working directly over the foot
    • Avoid hard floors when possible
    • Physical therapy with emphasis on strengthening the body's core
    • Firm, well-fitted shoes
    • Consider modification of mechanics
  • Physical Therapy
    • Emphasis on trunk (body and abdominal), back and pelvic muscles
    • Calf, FHL stretching exercises
    • Eccentric exercises
  • Adjunctive pain management
  • Immobilization
  • Orthotics
    • Emphasis on arch support

Procedural

Additional Modalities

  • Extracorporeal Shockwave Therapy
    • Moderate effectiveness, especially when combined with eccentric exercises
  • Low Level Laser Therapy
  • Topical Nitroglycerin Patches
    • Effective for pain but limited by headache side effects

Operative

  • Indications
    • Acute FHL tendon laceration
    • Progressive tendonitis that fails nonoperative management (8-12 weeks)
  • Technique
    • Open decompression
    • Arthroscopic decompression
    • Synovectomy

Rehab and Return to Play

Early rehab exercises for FHL tendinopathy

Rehabilitation

  • General
    • Should follow a progressive, periodized approach
    • Start with activity modification and FHL stretching
    • Advancing through eccentric strengthening, slow heavy resistance training
    • Culminate in sports specific exercises before return to play
    • Most patients recover within 3-6 months
  • Initial Phase: Activity Modification and Stretching (Weeks 0-4)[29]
    • Follow specific FHL stretching protocol, significantly reduces the need for surgery (OR 0.15)[30]
    • Eliminate activities involving repetitive forefoot push-off in extreme plantarflexion
    • Early exercises emphasize prolonged isometric contractions
  • Intermediate Phase: Progressive Loading (Weeks 4-12)[31]
    • Focuses on eccentric strengthening and heavy, slow resistance exercises
    • Tailored to the individual, progressively increasing load, volume, intensity, and time under tension
    • Exercises should target foot intrinsic muscles alongside the FHL
    • Evaluation of ROM, flexibility, and limb biomechanics to identify and address kinetic chain dysfunction
  • Advanced Phase: Sport-Specific Training (Weeks 12+)
    • Incorporates energy storage and release exercises, plyometrics, and sport-specific drills
    • Tailored ot individual goals

FHL Tendonitis Rehab Program

Return to Play/ Work

  • Return to play criteria
    • Pain-free sport-specific activities
    • Negative FHL stretch test
    • Single-leg heel raise ≥25 reps pain-free
    • Strength ≥90% of contralateral side
  • Timeline expectations[32]
    • 8-12 weeks for nonoperative return to full activity
    • 7-9 weeks post-surgical if operative intervention required

Complications and Prognosis

Hallux Rigidus[33]

Prognosis

  • General
    • 64% of patients achieving successful outcomes with nonoperative management alone
    • Surgical intervention yields good to excellent results in 93% of dancers and 82% of nondancers
  • Nonoperative outcomes
    • Success rates range from 44-64% when treatment includes the specific FHL stretching protocol[34]
    • Patients who complete the FHL stretching program are significantly less likely to require surgery (OR 0.15)[35]
  • Surgical outcomes
    • Highly favorable when conservative treatment fails
    • All-inside arthroscopic treatment demonstrates excellent long-term results (VAS, AOFAS)[36]

Complications

  • Hallux Rigidus
    • Patients with clinical hallux rigidus are more likely to require surgery (OR 2.4)[37]
  • Chronic misdiagnosis
    • Frequently misdiagnosed as plantar fasciitis, tarsal tunnel syndrome, or other conditions[38]
  • Tibial Nerve Injury

See Also

Internal

References

  1. ↑ 1.0 1.1 Gould, N : Stenosing tenosynovitis of the flexor hallucis longus tendon at the great toe. Foot Ankle 2:46–48, 1981.
  2. ↑ Shimozono, Yoshiharu, et al. "Cadaveric Study Evaluating the Potential for Hindfoot Endoscopy and Flexor Hallucis Longus Tendoscopy Using a 1.9-mm Diameter Needle Arthroscope." Foot & Ankle Orthopaedics 10.1 (2025): 24730114241310237.
  3. ↑ CHEMELLO, SARA, and HOSSEIN ANSARIPOUR. "Finite element analysis of socket optimization in accordance with the deformation of external surface of the stump." (2017).
  4. ↑ Elvan, Özlem, et al. "Anatomy of Master Knot of Henry: A morphometric study on cadavers." Acta Orthopaedica et Traumatologica Turcica 52.2 (2018): 134-142.
  5. ↑ Michelson, James D., et al. "What is the efficacy of a nonoperative program including a specific stretching protocol for flexor hallucis longus tendonitis?." Clinical Orthopaedics and Related Research® 479.12 (2021): 2667-2676.
  6. ↑ Michelson, James, and Laura Dunn. "Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment." Foot & ankle international 26.4 (2005): 291-303.
  7. ↑ Chun, Dong Il, et al. "Closed atraumatic complete rupture of the flexor halluces longus tendon during forward lunge exercise: A case report." Medicine 98.50 (2019): e18409.
  8. ↑ Noda, Daisuke, et al. "Subcutaneous rupture of the flexor hallucis longus tendon: a case report." The Journal of foot and ankle surgery 51.2 (2012): 234-236.
  9. ↑ Oloff, Lawrence M., and S. David Schulhofer. "Flexor hallucis longus dysfunction." The Journal of foot and ankle surgery 37.2 (1998): 101-109.
  10. ↑ Purushothaman, Rajesh, et al. "Hallux saltans due to flexor hallucis longus entrapment at a previously unreported site in an unskilled manual laborer: a case report." The Journal of foot and ankle surgery 51.3 (2012): 334-336.
  11. ↑ Sanhudo, José Antônio Veiga. "Stenosing tenosynovitis of the flexor hallucis longus tendon at the sesamoid area." Foot & ankle international 23.9 (2002): 801-803.
  12. ↑ Mira NO, Marulanda AF, Pena AC, Torres DC, Orrego JC. Study of Ballet Dancers During Cou-De-Pied Derrière with Demi-Plié to Piqué Arabesque. Journal of Dance Medicine & Science. 2019 Dec 15;23(4):150-8.
  13. ↑ Michelson, James, and Laura Dunn. "Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment." Foot & ankle international 26.4 (2005): 291-303.
  14. ↑ Oloff, Lawrence M., and S. David Schulhofer. "Flexor hallucis longus dysfunction." The Journal of foot and ankle surgery 37.2 (1998): 101-109.
  15. ↑ 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. 78A:1491–1500, 1996.
  16. ↑ Cooper, ME, Wolin, PM: Os trigonum syndrome with flexor hallucis longus tenosynovitis in a professional football referee, Med. Sci. Sports Exerc. 31:S493–S496, 1999.
  17. ↑ Romash, MM : Closed rupture of the flexor hallucis longus tendon in a long distance runner: report of a case and review of the literature, Foot Ankle Int. 15:433–436, 1994.
  18. ↑ Olden, Theresa Rebecca, and Jacques Vallotton. "Endoscopic tenolysis of flexor hallucis longus tendon: surgical technique." Arthroscopy Techniques 9.9 (2020): e1269-e1273.
  19. ↑ Oloff, Lawrence M., and S. David Schulhofer. "Flexor hallucis longus dysfunction." The Journal of foot and ankle surgery 37.2 (1998): 101-109.
  20. ↑ Michelson, James D., et al. "What is the efficacy of a nonoperative program including a specific stretching protocol for flexor hallucis longus tendonitis?." Clinical Orthopaedics and Related Research® 479.12 (2021): 2667-2676.
  21. ↑ owley KM, Jarvis DN, Kurihara T, Chang YJ, Fietzer AL, Kulig K. Toe flexor strength, flexibility and function and flexor hallucis longus tendon morphology in dancers and non-dancers. Medical problems of performing artists. 2015 Sep 1;30(3):152-6
  22. ↑ Michelson, James, and Laura Dunn. "Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment." Foot & ankle international 26.4 (2005): 291-303.
  23. ↑ Becciolini, Marco, et al. "Intermittent flexor hallucis longus dislocation: ultrasound findings." Journal of Ultrasound 28.1 (2025): 217-221.
  24. ↑ Michelson, James, and Laura Dunn. "Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment." Foot & ankle international 26.4 (2005): 291-303.
  25. ↑ Donovan, Andrea, et al. "Plantar tendons of the foot: MR imaging and US." Radiographics 33.7 (2013): 2065-2085.
  26. ↑ Martinez-Salazar, Edgar Leonardo, et al. "Hallux saltans due to stenosing tenosynovitis of flexor hallucis longus: dynamic sonography and arthroscopic findings." Skeletal radiology 47.5 (2018): 747-750.
  27. ↑ Walter HL, Docherty CL, Schrader J. Ground reaction forces in ballet dancers landing in flat shoes versus pointe shoes. Journal of Dance Medicine & Science. 2011 Jun 15;15(2):61-4.
  28. ↑ Michelson, James D., et al. "What is the efficacy of a nonoperative program including a specific stretching protocol for flexor hallucis longus tendonitis?." Clinical Orthopaedics and Related Research® 479.12 (2021): 2667-2676.
  29. ↑ Kakavas, Georgios, et al. "Neuroplastic periodization in tendinopathy." British Medical Bulletin 154.1 (2025): ldaf006.
  30. ↑ Michelson, James D., et al. "What is the efficacy of a nonoperative program including a specific stretching protocol for flexor hallucis longus tendonitis?." Clinical Orthopaedics and Related Research® 479.12 (2021): 2667-2676.
  31. ↑ Crowe, Lindsay AN, et al. "Pathways driving tendinopathy and enthesitis: siblings or distant cousins in musculoskeletal medicine?." The Lancet Rheumatology 5.5 (2023): e293-e304.
  32. ↑ Oloff, Lawrence M., and S. David Schulhofer. "Flexor hallucis longus dysfunction." The Journal of foot and ankle surgery 37.2 (1998): 101-109.
  33. ↑ Case courtesy of The Radswiki, Radiopaedia.org, rID: 11470
  34. ↑ Michelson, James, and Laura Dunn. "Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment." Foot & ankle international 26.4 (2005): 291-303.
  35. ↑ Michelson, James D., et al. "What is the efficacy of a nonoperative program including a specific stretching protocol for flexor hallucis longus tendonitis?." Clinical Orthopaedics and Related Research® 479.12 (2021): 2667-2676.
  36. ↑ Feng, Shi-Ming, et al. "Flexor hallucis longus tendon impingement syndrome: all-inside arthroscopic treatment and long-term follow-up." The Journal of Foot and Ankle Surgery 59.6 (2020): 1197-1200.
  37. ↑ Michelson, James D., et al. "What is the efficacy of a nonoperative program including a specific stretching protocol for flexor hallucis longus tendonitis?." Clinical Orthopaedics and Related Research® 479.12 (2021): 2667-2676.
  38. ↑ Michelson, James, and Laura Dunn. "Tenosynovitis of the flexor hallucis longus: a clinical study of the spectrum of presentation and treatment." Foot & ankle international 26.4 (2005): 291-303.
Created by:
John Kiel on 26 June 2019 22:07:58
Authors:
Last edited:
12 February 2026 19:02:05
Categories:
Retrieved from "https://wikism.org/w/index.php?title=Flexor_Hallucis_Longus_Tendinopathy&oldid=40569"