Flexor Hallucis Longus Tendon Rupture: Diagnosis and Surgical Repair

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) tendon rupture — complete discontinuity of the tendon that flexes the great toe — is an uncommon but functionally significant injury that primarily affects dancers, gymnasts, and jumping athletes, though it can occur in any patient with chronic FHL tendinopathy at the fibro-osseous tunnel. Unlike Achilles tendon ruptures, FHL ruptures are frequently misdiagnosed as ankle sprains, hallux rigidus, or sesamoid injuries, and a delay in diagnosis significantly affects surgical repair candidacy.

Anatomy and Mechanism

The FHL tendon originates in the posterior leg (flexor hallucis longus muscle), passes through a fibro-osseous tunnel at the posterior ankle adjacent to the os trigonum and sustentaculum tali, crosses the plantar foot in the master knot of Henry, and inserts into the distal phalanx of the hallux. The FHL is the primary flexor of the interphalangeal joint of the great toe and a significant dynamic stabilizer of the medial column during push-off. Rupture mechanism: acute rupture typically occurs from forced dorsiflexion of the great toe during vigorous push-off (landing from a jump, sudden direction change); chronic rupture results from progressive tendinopathy at the fibro-osseous tunnel with progressive attrition tearing — the most common pattern. Clinical diagnosis: inability to flex the interphalangeal joint of the hallux against resistance (the specific test for FHL function — the patient cannot flex the tip of the great toe while the MTP joint is stabilized); the hallux may adopt a claw position from unopposed extensor tone; the proximal tendon stump may be palpable in the posteromedial ankle region. MRI confirms complete rupture and characterizes the gap and degree of retraction.

Surgical Management

Acute repair (within 3–4 weeks of rupture): end-to-end primary repair through a posteromedial ankle approach; FHL tendon sheath release allows mobilization; repair with non-absorbable sutures using a Krackow or modified Bunnell technique; 6 weeks non-weight-bearing, gradual return to activity at 4–6 months. Chronic rupture with retraction: primary repair may not be possible — FHL-to-FDL (flexor digitorum longus) tenodesis produces acceptable function by anchoring the remaining distal FHL stump to the FDL tendon; interphalangeal joint arthrodesis as an alternative for hallux instability. Dr. Biernacki at Balance Foot & Ankle evaluates FHL function in patients with posterior ankle pain and hallux weakness, and performs FHL repair and reconstruction for complete ruptures. Call (810) 206-1402 at our Bloomfield Township or Howell office.

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In-Office Treatment at Balance Foot & Ankle

If home care isn’t resolving your your foot or ankle concern, a visit with a board-certified podiatrist is the fastest path to accurate diagnosis and a personalized plan. At Balance Foot & Ankle Specialists, Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin offer same-week appointments at both our Howell and Bloomfield Township offices. We perform on-site diagnostic ultrasound, digital X-ray, conservative care, advanced regenerative treatments, and minimally invasive surgery when indicated.

Call (810) 206-1402 or request an appointment online. Most insurance plans accepted, including Medicare, Blue Cross Blue Shield, Aetna, Cigna, and United Healthcare.

Frequently Asked Questions

When should I see a podiatrist?

See a podiatrist for any foot or ankle pain that persists more than 2 weeks, doesn’t improve with rest, limits your daily activities, or is accompanied by swelling, numbness, or skin changes. People with diabetes or circulation problems should see a podiatrist regularly even without symptoms.

What does a podiatrist treat?

Podiatrists diagnose and treat all conditions of the foot, ankle, and lower leg including plantar fasciitis, bunions, hammertoes, toenail problems, heel pain, nerve pain, diabetic foot care, sports injuries, fractures, and foot deformities — both surgically and non-surgically.

What can I expect at my first podiatry visit?

Your first visit includes a full medical history, physical examination of your feet and gait, and in-office diagnostic imaging if needed (X-rays, ultrasound). We’ll discuss your diagnosis and create a plan tailored to your foot type. Most visits take 30–45 minutes.

Need Treatment at Balance Foot & Ankle?

Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin see patients at our Howell and Bloomfield Township offices.

Book Online or call (810) 206-1402

Most Common Mistake We See

The most common mistake we see is: Waiting too long before seeking care. Fix: any foot pain lasting more than 4 weeks, or any sudden severe symptom, deserves a professional evaluation rather than more rest.

Warning Signs That Need Same-Day Care