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Atlas · Lower Leg

Flexor Digitorum Longus

Flexor digitorum longus has a deep lower-leg belly and tendons that flex the tips of the second through fifth toes. Calf symptoms, tendon-course pain and pain under the forefoot must be examined as distinct possibilities. Its muscle belly is not in the sole.

Flexor Digitorum Longus
Body region
Lower Leg · Foot
Trigger points
4
documented in this muscle
Common symptoms
3
patterns cataloged
Contributors
3
Factors to assess

Muscle overview

Symptoms and first steps

Practical first steps

  • Choose secure footwear with enough toe space so the toes need not grip to retain the shoe.
  • Reduce repeated painful push-off temporarily and keep comfortable toe/ankle movement.
  • Do not apply forceful pressure to the sole as a way to reach the FDL belly.

When to seek assessment

  • New severe escalating leg pain, a tense swollen compartment, pain with passive toe movement or a cold/pale foot requires emergency assessment.
  • New foot drop, repeated foot slapping, progressive weakness or persistent numbness needs prompt neurological assessment.
  • New unilateral swelling/warmth, a suspected fracture or inability to bear weight warrants medical assessment before massage or loading. Breathlessness or chest pain with leg swelling is an emergency.

A toe-gripping complaint can involve long flexors, short intrinsic muscles, footwear or neurological overactivity. Isolated distal-toe flexion is more informative than assuming every curled toe is an FDL trigger point.

Examination, palpation and treatment evidence

Illustrated overview

Flexor Digitorum Longus · Anatomy 1

Anatomical view of the illustrated muscle.

Open full-size image

Trigger points

1. TrP1

Location. Deep back of leg

Trigger point map
Flexor Digitorum Longus — Flexor Digitorum Longus · Trigger-point examples 1Open full-size image

Regional muscle reference; this is not an individual map of the selected numbered trigger point.

Referred pain map
Flexor Digitorum Longus — Flexor Digitorum Longus · Referred-pain pattern 1Open full-size image

Regional muscle reference; this is not an individual map of the selected numbered trigger point.

Pain referral. Calf, sole of foot, toes

Pain Pattern

  • Posterior leg
  • Sole of foot
  • Toes
  • Calf

What This Pain Feels Like

Deep posterior-leg discomfort may coexist with lesser-toe or forefoot pain during push-off. Local metatarsal, joint and nerve causes remain important; a referral map does not establish that the leg muscle is the source.

What Patients Report

  • Deep calf ache
  • Sole of foot pain
  • Toe cramping
  • Pain when walking

What Makes It Worse

  • Toe flexion
  • Running
  • Climbing
  • Walking
Browse related exercises (1)

Symptoms patients report

Lesser-toe or forefoot pain during push-off Identify the involved toe and whether pain is beneath a metatarsal head, within a joint or along a tendon.

Toe cramping or curling Intermittent exertional cramp differs from a fixed deformity or involuntary flexion after neurological injury.

Deep posterior-leg discomfort The long-flexor belly is in the leg, with substantial overlap from neighboring deep and superficial muscles.

Contributors to assess

Repeated toe-grip demand Loose footwear that requires gripping, prolonged forefoot loading or a new running/dance load may provoke symptoms.

Local forefoot disease Metatarsal, joint, plantar-plate or nerve pain may change toe use and needs local assessment.

Neurological spasticity or fixed toe deformity Determine whether the toe position is dynamic or fixed before considering a muscle-weakening procedure.

For clinicians and supervised training

Clinical reference

The foot marker shows a foot/tendon symptom region. The FDL muscle belly lies in the lower leg; distinguish tendon-course pain from local forefoot and nerve findings.

Anatomy and palpation

Anatomical relationships

FDL arises from the posterior tibia in the deep posterior leg. Its tendon passes behind the medial malleolus, enters the plantar foot and divides into four slips to the distal phalanges of toes two through five. Quadratus plantae and lumbrical connections influence these tendons in the foot.[1][2]

  • Posteromedial tibia orients the deep leg belly.
  • Behind the medial malleolus, FDL tendon lies in the retromalleolar group of structures.
  • The distal toe joints and plantar tendon slips identify its action in the foot, not a foot muscle belly.

Nearby structures. Tibialis posterior and FHL are neighboring long tendons; the tibial nerve and posterior tibial vessels pass through the same retromalleolar region. Intrinsic toe flexors, plantar plates and digital nerves can account for similar forefoot symptoms.

Palpation

Patient position. Seated with the lower leg supported and foot accessible; keep the ankle and toes relaxed.

Find the landmarks

  • Posteromedial lower leg
  • Retromalleolar tendon region
  • Plantar lesser-toe tendon course

Examination sequence

  1. Inspect toe position, swelling and the precise painful plantar site.
  2. Use gentle toe-tip flexion to assess tendon movement, avoiding sustained pressure on the neurovascular tunnel.
  3. Record calf tenderness as regional when the belly cannot be distinguished. Assess local forefoot symptoms separately from the leg.

Document the findings

  • Reproducible tendon/forefoot symptoms with toe flexion, restricted motion or involuntary toe posture.
  • Tenderness under a metatarsal head is not direct evidence of an FDL belly lesion.

Limits and precautions

  • Avoid forceful probing between plantar metatarsal heads or behind the medial ankle.
  • Do not force a fixed toe deformity straight or stretch an acutely swollen painful foot.
[1][2]

Examination and tests

2

Resisted flexion of the lesser-toe tips[1]

Assess long-flexor action and distinguish distal-toe flexion from a general toe-grip task.

Position
Seated with the foot supported and the tested toe accessible.
Technique
Stabilize the middle phalanx and ask for gentle flexion at the distal interphalangeal joint against light resistance. Compare the symptomatic toe with adjacent toes and the other foot, recording pain location and control.
Positive finding
Familiar tendon-course/forefoot pain, weakness or abnormal involuntary toe flexion.
Interpretation
The action emphasizes the long flexor tendon; findings guide local tendon, neurological and forefoot assessment.
Limitations
FDL tendons are interconnected with intrinsic muscles, and pain alters effort. This does not validate a trigger point or independently diagnose a tendon lesion.

Toe extension across ankle positions[1][2]

Assess flexible versus fixed toe restriction and the influence of long-flexor tension.

Position
Seated or supine with the ankle and toes supported by a clinician.
Technique
Gently extend the lesser toes with the ankle relaxed/plantar flexed, then with modest dorsiflexion. Observe whether the curled position changes and where familiar pain occurs. Assess individual joints separately when restriction persists.
Positive finding
A toe position that changes with ankle angle, or a fixed painful joint restriction in both positions.
Interpretation
An ankle-position effect suggests a long-tendon contribution; persistent fixed restriction warrants joint/deformity assessment.
Limitations
This is an anatomy-informed examination without a validated FDL trigger-point cutoff. Stop at pain and do not force extension.

Distinguishing other causes

Metatarsalgia, plantar-plate or lesser-toe joint disease[1][3]

Findings that matter. Pain concentrated beneath a metatarsal head, toe drift, swelling or pain with local joint loading.

Next step. Perform a local forefoot examination; use imaging or foot-specialist assessment according to findings.

Digital/tibial nerve involvement[2]

Findings that matter. Burning, electric pain or numbness in toes/sole, rather than only a reproducible tendon-load ache.

Next step. Assess sensation, neurological signs and local compression possibilities without presuming muscle referral.

Bone stress injury[3]

Findings that matter. Focal metatarsal or tibial bone tenderness and increasing impact pain after a training increase.

Next step. Reduce impact and arrange assessment; early normal radiographs do not exclude stress injury.

Neurological spasticity or fixed claw-toe deformity[5]

Findings that matter. Persistent involuntary toe flexion after neurological injury or joints that remain restricted across ankle positions.

Next step. Assess passive range and the neurological diagnosis; distinguish dynamic overactivity from fixed contracture before intervention.

Treatment selection and progression

Exercise and rehabilitation

Controlled lesser-toe flexion and push-off progression[1]

Consider when. A load-sensitive presentation with local bone, joint and neurological concerns assessed.

Practice light toe-tip flexion without clawing the whole foot, then supported heel rises if comfortable. Maintain control and stop short of a painful cramp.

Dose and review
Illustrative entry point: a few slow repetitions followed by a walking check; add a small set only when the response is stable.
Progression
Increase resistance or weight-bearing demand before adding repetitive running or dance push-off.
Stop or reassess
Stop for a painful catch, new swelling, numbness or loss of toe control.
Evidence and limits
Anatomy-informed rehabilitation; no FDL-MPS trial or fixed dose is established by these references.

Self-care and activity

Secure footwear and reduce painful forefoot pressure[1][3]

Consider when. Symptoms are provoked by toe gripping, narrow shoes or repeated forefoot pressure.

Use well-secured shoes with adequate toe space and choose a comfortable walking surface. Avoid footwear that requires constant toe gripping; a clinician can assess persistent focal pressure or deformity.

Dose and review
Compare a short, consistent walking task after a fit change and retain it only if beneficial.
Progression
Restore longer walking before repeated high-force push-off, monitoring local forefoot symptoms.
Stop or reassess
Seek assessment for skin damage, persistent focal bone pain or progressive toe deformity.
Evidence and limits
Practical management of a defined provoking task; footwear response does not identify the FDL belly as the pain source.

Exercise and rehabilitation

Graded walking and forefoot-load exposure[1]

Consider when. Ordinary walking is possible without acute injury or progressive neurological signs.

Start with level walking that keeps the toes comfortable and does not require forceful gripping. Add duration before speed, inclines or jumping, and keep toe-strength work at a manageable dose.

Dose and review
Choose the current comfortable duration and allow recovery from harder forefoot-loading sessions.
Progression
Use next-day walking and toe control to decide whether to add one demand at a time.
Stop or reassess
Stop for a limp, focal bone-load pain, worsening involuntary curling or numbness.
Evidence and limits
Functional rehabilitation extrapolated from anatomy and the assessed presentation; not a validated FDL trigger-point protocol.

Clinician-delivered care

Botulinum toxin for diagnosed flexor digitorum longus spasticity[5]

Consider when. Neurological spasticity, such as after stroke, in which involuntary flexor digitorum longus activity interferes with lesser-toe position, shoe tolerance or walking. Ordinary cramping, tendon pain and a tender point do not establish this indication.

A rehabilitation/spasticity specialist evaluates the whole limb, passive range, weakness and the role of each involved muscle. If appropriate, use guided muscle localization and pair treatment with rehabilitation or orthotic care to address lesser-toe position, shoe tolerance or walking.

Dose and review
Drug selection and dose are prescribed individually. Agree on a review around 4–6 weeks and reassess before any repeat treatment.
Progression
Compare the agreed functional goal and adverse effects, not tone alone; a fixed contracture or weakness may need a different strategy.
Stop or reassess
Report new troublesome weakness or falls. Difficulty swallowing or breathing after toxin treatment requires urgent medical help.
Evidence and limits
The US label supports adult lower-limb spasticity. Its 468-person post-stroke trial used several muscles and followed participants for 12 weeks; benefits in ankle tone/global response at weeks 4/6 do not establish isolated-muscle pain relief or efficacy for MPS.

Reassessment and follow-up

  • Repeat toe-tip flexion and the same walking/push-off task.
  • Check flexible versus fixed toe posture and the precise plantar pain site.
  • Revisit local joint/bone/nerve causes if symptoms persist despite sensible load adjustment.

Evidence and sources

  1. University of Washington Muscle Atlas: Flexor digitorum longus

    2026 · Institutional anatomy reference

    Undated anatomy page, verified September 2026; the year records this review. Supports attachments and actions, not diagnostic accuracy of palpation or a trigger-point map. No atlas illustration reproduced.

  2. Anatomy, Bony Pelvis and Lower Limb: Leg Posterior Compartment

    2026 · Anatomy reference

    Deep posterior compartment and neurovascular relationships; reviewed September 2026. Does not validate selective deep-muscle palpation or the legacy foot point coordinates.

  3. AAOS OrthoInfo: Stress Fractures of the Foot and Ankle

    2026 · Professional society clinical information

    Undated page verified September 2026; focal bone-load pain and the limits of early plain radiography.

  4. AAOS OrthoInfo: Compartment Syndrome

    2026 · Professional society clinical information

    Undated page verified September 2026; differentiates acute emergencies from exertional presentations. Muscle palpation cannot exclude either.

  5. BOTOX (onabotulinumtoxinA): US prescribing information

    2026 · Official prescribing information

    Adult lower-limb spasticity indication includes tibialis posterior, FHL and FDL. The 468-person post-stroke trial followed a multi-muscle protocol for 12 weeks; ankle tone/global response at weeks 4/6 cannot establish isolated toe-muscle analgesia or an MPS indication.

Associated Trigger Points