Flexor Hallucis Longus Tendinopathy: Diagnosis & Treatment | Michigan

Quick answer: Flexor Hallucis Longus Tendinopathy Michigan is a common foot/ankle topic that affects many patients. Effective treatment starts with a targeted diagnosis, conservative-first treatment, and escalation only when needed. We treat this regularly at our Howell and Bloomfield Township practices. Book online, or call (810) 206-1402.

Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Township, MI. Last updated April 2026.

Flexor hallucis longus (FHL) tendinopathy is degeneration or inflammation of the tendon that flexes the big toe, causing pain along the inner ankle, under the first metatarsal, or at the big toe itself — particularly with push-off and toe flexion activities. It is sometimes called “dancer’s tendinitis” because it commonly affects ballet dancers but also occurs in runners, hikers, and anyone with repetitive toe flexion demands. Dr. Tom Biernacki, DPM at Balance Foot & Ankle in Howell and Bloomfield Township, Michigan evaluates and treats FHL tendinopathy.

Anatomy: The Flexor Hallucis Longus Tendon

The flexor hallucis longus (FHL) muscle originates in the lower leg and its tendon passes behind the medial ankle through a fibro-osseous tunnel beneath the sustentaculum tali (a bony shelf of the calcaneus), then courses under the first metatarsal to insert at the base of the distal phalanx of the great toe. It is the primary big toe flexor and a secondary ankle plantarflexor. The FHL tendon passes through a narrow tunnel behind the medial malleolus — a zone of vulnerability where it can develop tenosynovitis (inflammation of the tendon sheath), trigger toe (a catching or triggering sensation), or longitudinal tears similar to those seen in the peroneal tendons on the lateral side.

Symptoms and Presentation

FHL tendinopathy presents with: pain and swelling along the medial ankle posterior to the medial malleolus (the inner bump), pain under the first metatarsal shaft during push-off, pain at the base of the big toe with forced dorsiflexion, and in trigger toe cases, a locking or snapping sensation when the big toe flexes or extends. The condition worsens with toe push-off intensive activities — running (particularly uphill), ballet, dance on pointe, and hiking. Passive big toe dorsiflexion with ankle dorsiflexion (the “FHL stretch test”) often reproduces the medial ankle or midfoot pain by tensioning the tendon.

Diagnosis

Diagnosis is clinical with imaging confirmation. Palpation along the FHL course behind the medial ankle, under the midfoot, and at the first metatarsal reproduces characteristic pain. Musculoskeletal ultrasound is the most accessible tool — dynamic assessment can visualize the tendon sheath fluid, tendon thickening, and triggering during passive toe motion. MRI provides superior evaluation of tendon integrity, longitudinal tears, and stenosing tenosynovitis at the fibro-osseous tunnel. The FHL tunnel at the posterior talus (“master knot of Henry” area) is a common site of stenosing tenosynovitis requiring surgical release in refractory cases.

Conservative Treatment

Activity modification to reduce toe push-off loading is the first step — modifying training surfaces (flat rather than uphill), reducing running mileage, and eliminating dance or pointe work during acute flares. Custom orthotics with a Morton’s extension (rigid extension under the first metatarsal and great toe to reduce FHL excursion during push-off) reduce tendon loading during gait. Corticosteroid injection into the FHL tendon sheath reduces tenosynovitis — injection directly into the tendon substance is avoided due to rupture risk. Physical therapy addressing gastrocnemius flexibility and FHL eccentric strengthening at pain-free range supports long-term recovery.

Surgical Treatment

Surgical FHL release is indicated for trigger toe that has not responded to conservative management, stenosing tenosynovitis at the posterior talar tunnel causing persistent pain and catching, and longitudinal FHL tears that have not healed with conservative care. Endoscopic FHL release is performed through a small posterior ankle portal — recovery is faster than open release. Dancers with FHL trigger toe typically return to ballet in 3–4 months after endoscopic release with satisfactory outcomes in over 90% of appropriately selected patients.

Most Common Diagnostic Mistake

The most common mistake is confusing FHL tendinopathy with posterior tibial tendinopathy (PTTD) because both cause medial ankle pain. PTTD involves the posterior tibial tendon, which passes anterior to the medial malleolus and inserts at the navicular; FHL passes posterior to the medial malleolus and inserts at the big toe. Palpating pain posterior to the medial malleolus that reproduces with passive big toe dorsiflexion (tensioning the FHL specifically) distinguishes FHL tendinopathy from PTTD, which is reproduced by resisted foot eversion and pain at the navicular insertion.

When to See Dr. Biernacki

See a podiatrist if you have medial ankle or midfoot pain with running or dance that has persisted more than 4–6 weeks, if you experience a triggering or catching sensation in the big toe, or if you are a dancer with posterior ankle pain on pointe. Dr. Biernacki provides in-office ultrasound evaluation, FHL tendon sheath injection, custom orthotics with Morton’s extension, and surgical consultation coordination for refractory cases. Book online or call (810) 206-1402 — Howell and Bloomfield Township, Michigan.

When to See a Podiatrist for This Type of Pain

If your pain has lasted longer than 3-4 weeks despite home treatment, is interfering with daily activities, or includes redness, swelling, or warmth, it’s time to schedule an evaluation. At Balance Foot & Ankle Specialists, Dr. Tom Biernacki and his team specialize in same-day diagnosis and conservative treatment plans tailored to your activity level and goals. Most patients are walking pain-free within 4-6 weeks of starting our protocol.

Red flags that warrant immediate care: sharp pain after a fall, inability to bear weight, visible deformity, numbness or tingling, fever with foot pain, or any open wound on a diabetic foot. Don’t wait — early treatment dramatically improves outcomes and prevents chronic complications.

In-Office Treatment at Balance Foot & Ankle

If home treatment isn’t providing relief for your Achilles tendon conditions, our podiatry team at Balance Foot & Ankle can help with same-day evaluations and advanced in-office care.