Flexor Digitorum Longus Tendon Tear 2026 | DPM

Tendon	Location	Function	Tear Presentation	Clinical Test	Typical Treatment
FDL (Flexor Digitorum Longus)	Medial ankle behind PTT; plantar foot to lesser toe tips	Plantarflexes toes 2–5; stabilizes forefoot push-off	Medial ankle pain; weakness of lesser toe flexion; often misdiagnosed as PTT injury	Resisted toe flexion test (toes 2–5); tenderness along medial ankle and plantar foot	Repair if acute; FDL-to-FHL tenodesis for chronic/degenerative tears
FHL (Flexor Hallucis Longus)	Posterior ankle behind fibula; plantar foot to hallux	Plantarflexes great toe; key for push-off and ballet	Posterior ankle pain; hallux flexion weakness; triggering hallux (stenosing tenosynovitis)	Resisted hallux plantarflexion; positive Hallux Bowstringing test	Endoscopic FHL release for tenosynovitis; tendon repair or hallux fusion for rupture
PTT (Posterior Tibial Tendon)	Medial ankle behind medial malleolus; navicular insertion	Supinates foot; primary arch dynamic support	Adult flatfoot; medial ankle pain; progressive arch collapse; positive “too many toes” sign	Single-leg heel rise test (absent in Stage II+)	Stage-based: orthotics → FDL transfer + osteotomy → triple arthrodesis

Treatment	Indication	Technique	Expected Outcome	Recovery
Conservative (Boot + PT)	Partial tear; low-demand patient; tenosynovitis	4–6 weeks immobilization; physical therapy for strengthening	60–70% improvement for partial tears; complete tears rarely heal conservatively	6–8 weeks to return to activity
Primary FDL Repair	Acute complete tear (<6 weeks); adequate tissue quality	End-to-end repair with non-absorbable suture; augmented with Krackow technique	80–90% good functional outcomes	NWB 6 weeks; 4–6 months to full activity
FDL-to-FHL Tenodesis	Chronic FDL tear; degenerated tissue; insufficient stump length	FDL sutured side-to-side to FHL at plantar arch level; FHL drives both	85% good-to-excellent; minor hallux flexion strength reduction (well-tolerated)	NWB 4–6 weeks; 3–4 months return to sport
FDL Reconstruction with Allograft	Large gap; failed prior repair; revision	Tendon allograft bridging defect; secured proximally and distally	75–80% functional restoration	NWB 8 weeks; 5–6 months to sport

Quick answer: Flexor Digitorum Longus Tendon Tear Medial Ankle Michigan Podiatrist is a common foot/ankle topic that affects many patients. The 2026 evidence-based approach combines proper diagnosis, conservative-first treatment, and escalation only when needed. We treat this regularly at our Howell and Bloomfield Hills practices. Call (810) 206-1402.

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FDL Tendon Anatomy and Function

The flexor digitorum longus (FDL) originates on the posterior tibia, passes behind the medial malleolus in the second compartment of the flexor retinaculum (between the posterior tibial tendon anteriorly and the FHL posteriorly), crosses the knot of Henry beneath the navicular, and splits into four slips to the distal phalanges of the lesser toes. Its primary actions are plantar flexion of toes 2–5 and supplemental arch support during push-off. When the FDL is compromised, patients lose lesser toe flexion strength and experience medial arch fatigue.

Causes of FDL Tendon Injury

FDL injuries occur through several mechanisms. Acute tears result from direct trauma, forced dorsiflexion, or avulsion at the knot of Henry. Chronic tendinopathy develops from repetitive overload — common in runners, dancers, and patients with progressive adult flatfoot deformity who overload the medial arch stabilizers. Constriction within the flexor retinaculum can cause a stenosing tenosynovitis similar to trigger finger (trigger toe). FDL pathology frequently coexists with PTTD — both tendons are stressed by progressive flatfoot collapse — and isolated FDL tears are often found incidentally on MRI ordered for suspected PTTD.

Symptoms and How It Differs from PTTD

FDL tendinopathy produces posteromedial ankle pain similar to PTTD but with distinctive features: tenderness is slightly more posterior and inferior; pain is reproduced by resisted lesser toe plantarflexion; and patients may report the toes “not gripping” properly during push-off. Unlike PTTD, single-leg heel-rise is typically preserved unless concurrent flatfoot is severe. A palpable nodule or triggering phenomenon along the tendon course suggests stenosis or longitudinal tear. Differentiation from tarsal tunnel syndrome requires careful neurological examination and EMG/nerve conduction studies.

Diagnosis with MRI and Ultrasound

MRI is the gold standard for FDL pathology assessment — providing high-resolution visualization of tendon continuity, peritendinous fluid, and signal changes indicating degeneration or partial/complete tear. Dr. Biernacki also uses diagnostic ultrasound for dynamic assessment — evaluating tendon gliding, detecting nodules, and guiding injections. Ultrasound is particularly useful for evaluating constriction at the flexor retinaculum and the knot of Henry where the FDL crosses the FHL.

Treatment: Conservative and Surgical Options

Conservative management includes CAM boot immobilization for 4–6 weeks during acute flares; custom orthotics with medial arch support and heel lift to reduce FDL tensile load; physical therapy targeting intrinsic foot strengthening and proximal lower-extremity mechanics; and corticosteroid or PRP injection for persistent tendinopathy. Surgical options for refractory cases include FDL tenosynovectomy and debridement for stenosis; primary repair or imbrication for partial longitudinal tears; and FDL-to-FHL tenodesis for complete or irreparable FDL tears — transferring FDL function to the more powerful adjacent FHL tendon with minimal functional sacrifice, since both tendons share some function through the master knot of Henry.

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Frequently Asked Questions

When should I see a podiatrist?

If symptoms persist past 2 weeks, affect your normal activity, or are accompanied by red-flag symptoms (warmth, redness, swelling, inability to bear weight).

What does treatment cost?

Most diagnostic visits and conservative treatments are covered by Medicare and major insurers. Out-of-pocket costs vary by your specific plan.

How quickly can I get an appointment?

Most non-urgent cases see us within 5 business days. Urgent cases (sudden pain, possible fracture) typically same or next business day.

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.