Flexor Digitorum Longus Trigger Points

Introduction

The flexor digitorum longus (FDL) is a key lower leg muscle responsible for toe flexion and foot stabilization. When trigger points develop in this muscle, they can cause pain in the arch, toes, and ankle, often mimicking plantar fasciitis, tarsal tunnel syndrome, or neuropathy.

Name and Area

  • Name: Flexor Digitorum Longus (FDL)

  • Area: Located on the posterior lower leg, running from the tibia to the distal phalanges of toes 2–5.

Indications

Flexor digitorum longus trigger points may contribute to:

  • Pain in the Arch of the Foot (Mistaken for Plantar Fasciitis or Arch Strain)

  • Pain That Radiates to the Toes (Can Mimic Metatarsalgia or Morton’s Neuroma)

  • Tightness or Cramping in the Toes (Especially with Walking or Running)

  • Weakness in Toe Flexion (Difficulty Gripping the Ground While Walking or Running)

  • Pain That Increases When Walking Barefoot on Hard Surfaces

  • Aching or Burning Sensation in the Foot or Lower Leg After Long Periods of Standing

Pain from this muscle is often mistaken for plantar fasciitis, nerve compression, or toe joint arthritis.

Muscle Action

  • Flexes the Toes (Digits 2–5): Bends the toes at the distal interphalangeal (DIP) joints.

  • Assists in Foot Plantarflexion: Helps point the foot downward.

  • Supports the Medial Arch: Works with the tibialis posterior to maintain foot stability.

The FDL is crucial for proper toe movement, push-off during walking and running, and arch support.

Signs and Symptoms

Individuals with flexor digitorum longus trigger points often report:

  • Pain in the Arch of the Foot, Especially Near the Toes

  • Difficulty Flexing the Toes (Pain When Curling the Toes While Walking or Running)

  • Burning or Tingling Sensation in the Foot (Mistaken for Nerve Pain or Neuropathy)

  • Pain That Feels Worse After Walking or Standing for Long Periods

  • Toe Stiffness or Weakness, Especially in the Morning or After Activity

Pain worsens with prolonged standing, walking, or wearing unsupportive footwear.

Perpetuating Factors

Common causes of flexor digitorum longus trigger points include:

  • Wearing Tight or Narrow Shoes (E.g., High Heels, Cleats, or Dress Shoes)

  • Overuse From Running, Sprinting, or Jumping

  • Foot Instability Due to High Arches or Flat Feet

  • Walking or Standing for Long Periods on Hard Surfaces (Retail Workers, Runners, Hikers)

  • Toe-Curling Movements or Foot Strain from Certain Sports (Dancing, Ballet, or Soccer)

Trigger Point Referral Pattern

Trigger points in the flexor digitorum longus refer pain to:

  • The arch of the foot (Can Mimic Plantar Fasciitis or Foot Cramps)

  • The bottom of the toes (Mistaken for Metatarsalgia or Morton’s Neuroma)

  • The inner ankle (Can Be Misdiagnosed as Tarsal Tunnel Syndrome or Achilles Tendinitis)

Pain from this muscle is often confused with plantar fasciitis, nerve entrapment, or metatarsalgia.

Differential Diagnosis

Flexor digitorum longus trigger points may be mistaken for:

  • Plantar Fasciitis (Pain in the Arch and Heel, Especially in the Morning)

  • Morton’s Neuroma (Pain Between the Toes With a "Pebble in the Shoe" Sensation)

  • Tarsal Tunnel Syndrome (Burning Pain and Numbness in the Foot and Toes)

  • Metatarsalgia (Pain in the Ball of the Foot, Worsened by Walking or Running)

  • Stress Fractures in the Metatarsals (Pain That Worsens With Impact Activities)

A thorough foot examination is necessary to rule out these conditions.

Associated Trigger Points

Flexor digitorum longus trigger points often co-exist with:

  • Plantar Fascia (Arch Pain and Foot Stiffness, Often Related to Foot Overuse)

  • Flexor Digitorum Brevis (Pain in the Foot and Toes, Affects Toe Control and Push-Off Strength)

  • Tibialis Posterior (Pain Along the Inner Ankle and Foot, Affects Arch Support and Stability)

  • Peroneus Longus and Brevis (Lateral Foot and Ankle Pain, Can Affect Balance and Gait)

Anatomy and Innervation

Muscle Origin Insertion Innervation
Flexor Digitorum Longus Posterior tibia Distal phalanges of toes 2–5 Tibial nerve (L5–S2)

The FDL is innervated by the tibial nerve, which also controls toe flexion and foot stability.

Patient Examination

A comprehensive examination should include:

  • Palpation: Identify tender nodules along the posterior lower leg and arch of the foot.

  • Toe Flexion Strength Testing: Assess pain and weakness when curling the toes against resistance.

  • Gait Analysis: Look for abnormal foot movement patterns while walking or running.

  • Footwear Assessment: Determine if improper shoes are contributing to symptoms.

Corrective Actions

Dry Needling

  • Dry needling can release trigger points in the flexor digitorum longus, reducing muscle tightness and improving foot mobility.

Manual Therapy

  • Trigger Point Release: Apply direct pressure to tight spots along the lower leg and foot arch.

  • Massage Therapy: Helps improve circulation and reduce foot tension.

Stretching

  • Toe Flexor Stretch: Pull the toes backward gently while keeping the foot relaxed.

  • Foot Arch Stretch: Roll a tennis ball or massage ball under the foot to loosen tight muscles.

Strengthening Exercises

  • Toe Gripping Exercises: Strengthens the flexor digitorum longus and foot stabilizers.

  • Resistance Band Toe Flexion: Improves toe control and push-off strength.

  • Short Foot Exercise: Helps activate the arch and improve foot stability.

Postural and Footwear Adjustments

  • Wear Supportive Shoes with Proper Arch Support

  • Use Custom Orthotics to Improve Foot Alignment

  • Avoid Excessive Barefoot Walking on Hard Surfaces

Conclusion

The flexor digitorum longus plays a crucial role in toe flexion and arch support, but trigger points in this muscle can cause significant foot, toe, and arch pain. By incorporating dry needling, manual therapy, stretching, and strengthening exercises, individuals can reduce pain, improve mobility, and prevent future dysfunction.

➡️ Learn more about Trigger Points

Sources:

  • Travell, J. G., & Simons, D. G. (1983). Myofascial Pain and Dysfunction: The Trigger Point Manual (2nd ed.). Williams & Wilkins.

  • Simons, D., & Travell, J. (1999). The Trigger Point Manual, Volume 2: The Lower Extremities. Williams & Wilkins.