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

🩺 Medically Reviewed by: Dr. Thomas Biernacki, DPM — Board-Certified Podiatrist | Last Updated: April 2026 | Reading Time: 12 min

Quick Answer: FDL tendon transfer is the gold-standard surgical reconstruction for Stage II posterior tibial tendon dysfunction (PTTD) when conservative treatment fails after 3–6 months. The flexor digitorum longus tendon replaces the damaged posterior tibial tendon, restoring medial arch support and correcting progressive flatfoot deformity. Combined with a medializing calcaneal osteotomy, success rates exceed 90% with proper rehabilitation over 3–6 months.

📑 Table of Contents

• Understanding Posterior Tibial Tendon Dysfunction
• PTTD Staging: Johnson and Strom Classification
• Conservative Treatment Before Surgery
• When Is FDL Transfer Surgery Recommended?
• Surgical Anatomy: The FDL Tendon
• The FDL Transfer Procedure Step by Step
• Medializing Calcaneal Osteotomy
• Recovery Timeline and Weight-Bearing Progression
• Post-Surgical Rehabilitation Protocol
• Long-Term Outcomes and Success Rates
• Potential Complications and Risk Management
• Foot Care Products for Recovery
• Frequently Asked Questions
• Sources

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Understanding Posterior Tibial Tendon Dysfunction

The posterior tibial tendon is the single most important dynamic stabilizer of the medial longitudinal arch. Running behind the medial malleolus and inserting broadly on the navicular, cuneiforms, and metatarsal bases, this tendon works continuously during gait to lock the midtarsal joint and convert the foot from a flexible adaptor to a rigid lever for push-off. When the posterior tibial tendon degenerates — through chronic overuse, inflammatory arthropathy, or vascular compromise — the arch progressively collapses, the hindfoot drifts into valgus, and the forefoot abducts. This cascade is posterior tibial tendon dysfunction, and it affects approximately 3.3% of women over age 40.

What makes PTTD particularly challenging is its progressive nature. Without intervention, Stage II flexible flatfoot inevitably advances to Stage III rigid deformity, at which point simple tendon transfer is no longer sufficient and more extensive arthrodesis procedures become necessary. This is why early recognition and appropriate surgical timing are critical — the window for joint-sparing reconstruction closes as the deformity becomes fixed.

At Balance Foot & Ankle, we evaluate PTTD using a comprehensive assessment that includes the single-limb heel rise test, the “too many toes” sign, and advanced imaging to determine the exact stage of dysfunction and guide treatment decisions. Our goal is always to exhaust appropriate conservative measures first while monitoring for progression that would warrant surgical intervention.

PTTD Staging: The Johnson and Strom Classification

Stage I represents tenosynovitis with tendon inflammation but no significant deformity. The tendon is swollen and painful along the medial ankle, but the arch height is maintained and the patient can still perform a single-limb heel rise, though it may be painful. Conservative treatment with immobilization, custom orthotics, and physical therapy is highly effective at this stage, with most patients achieving full symptom resolution without surgery.

Stage II is where FDL transfer becomes the primary surgical consideration. The tendon has elongated or partially ruptured, the arch has collapsed, and the hindfoot has shifted into valgus — but the deformity remains flexible, meaning it can be manually corrected. The patient typically cannot perform a single-limb heel rise or can only manage a partial rise. Stage II is further subdivided: Stage IIA involves hindfoot valgus less than 30% of talar uncovering, while Stage IIB shows greater forefoot abduction with more than 30% uncovering on anteroposterior radiographs.

Stage III marks the transition to rigid deformity. The subtalar joint has developed fixed valgus that cannot be passively corrected, and secondary arthritic changes have begun in the triple joint complex. FDL transfer alone is insufficient at this stage — subtalar or triple arthrodesis is typically required. Stage IV, added by Myerson, involves deltoid ligament incompetence with lateral tibiotalar tilt, creating ankle valgus in addition to hindfoot deformity.

Conservative Treatment Before Surgery

Surgery for PTTD is never the first option. A minimum of 3–6 months of structured conservative treatment should be attempted before considering FDL transfer, and many Stage I and early Stage II patients respond well to non-operative management. The conservative protocol begins with immobilization — either a CAM walker boot or a short leg cast — for 4–6 weeks to reduce acute inflammation. This is followed by transition to a custom ankle-foot orthosis (AFO) or a rigid UCBL orthotic that controls hindfoot valgus.

Physical therapy targeting eccentric strengthening of the posterior tibial tendon has shown promise in early-stage disease, similar to the eccentric protocols used successfully for Achilles tendinopathy. The program typically progresses through isolated posterior tibial tendon exercises, intrinsic foot muscle activation, and progressive balance and proprioception training. Anti-inflammatory management with NSAIDs, ice, and activity modification supports the rehabilitation program.

The critical decision point comes when conservative measures fail to control symptoms and the deformity continues to progress. If radiographic measurements show increasing talar uncovering, loss of calcaneal pitch, or progressive hindfoot valgus despite bracing and therapy, surgical intervention should be discussed before the deformity becomes rigid and limits reconstructive options.

When Is FDL Transfer Surgery Recommended?

FDL transfer is specifically indicated for Stage II PTTD — the flexible flatfoot deformity that has failed adequate conservative treatment. The ideal surgical candidate has painful flatfoot with a flexible hindfoot that corrects on examination, an incompetent or severely degenerated posterior tibial tendon confirmed on MRI, failure of at least 3–6 months of conservative management, and sufficient bone stock for osteotomy fixation. The patient must also be motivated to comply with the extended non-weight-bearing recovery period.

Contraindications to isolated FDL transfer include rigid hindfoot deformity (Stage III or IV), significant subtalar arthritis on weight-bearing radiographs, severe peripheral vascular disease that compromises surgical healing, uncontrolled diabetes with active neuropathy or Charcot changes, and unrealistic patient expectations about recovery timeline and activity resumption. In these cases, alternative procedures such as subtalar arthrodesis, triple arthrodesis, or staged reconstruction may be more appropriate.

Surgical Anatomy: Why the FDL Tendon?

The flexor digitorum longus was chosen as the transfer tendon for several anatomically elegant reasons. First, the FDL runs in a sheath immediately adjacent to the posterior tibial tendon behind the medial malleolus, sharing a similar line of pull and moment arm around the subtalar joint axis. This means the transferred FDL can approximate the function of the native posterior tibial tendon without requiring significant rerouting or tunnel creation.

Second, harvesting the FDL creates minimal functional deficit. While the FDL normally controls lesser toe flexion at the DIP joints, the flexor hallucis longus (FHL) has interconnections through the knot of Henry that partially compensate for FDL loss. Most patients notice little to no difference in toe grip strength after FDL transfer, though some may have mild weakness of lesser toe flexion that rarely affects daily function or gait.

Third, the FDL has appropriate size and tensile strength. Though smaller than the posterior tibial tendon — approximately 30% of its cross-sectional area — the transferred FDL combined with the medializing calcaneal osteotomy provides sufficient dynamic medial arch support. The osteotomy shifts the mechanical axis to reduce the demand on the transferred tendon, creating a biomechanical environment where the smaller FDL can function effectively long-term.

The FDL Transfer Procedure Step by Step

The surgery is typically performed under general anesthesia with a popliteal nerve block for postoperative pain management. A thigh tourniquet provides a bloodless surgical field. The procedure involves multiple coordinated steps through two or three incisions.

Step 1: Medial exposure and PTT assessment. A curvilinear incision is made along the medial ankle, following the course of the posterior tibial tendon from behind the medial malleolus to its navicular insertion. The tendon sheath is opened, and the posterior tibial tendon is inspected. In Stage II disease, the tendon is typically elongated, thickened with mucinoid degeneration, and may have longitudinal splits or partial tears. The diseased tendon is debrided or excised, preserving the sheath as a bed for the transfer.

Step 2: FDL tendon harvest. The FDL is identified running deep and posterior to the posterior tibial tendon within the tarsal tunnel. The tendon is traced distally through the knot of Henry to its bifurcation point. The FDL is transected at the knot of Henry, and a side-to-side tenodesis is performed between the distal FDL stump and the intact FHL to maintain some lesser toe flexion. The proximal FDL is then mobilized and freed from its sheath to provide adequate excursion for transfer.

Step 3: Navicular tunnel preparation and tendon insertion. A bone tunnel is created in the navicular tuberosity using a 4.5mm or 5.0mm drill. The tunnel is directed from dorsomedial to plantar-lateral. The FDL tendon is passed through the tunnel and secured under appropriate tension — with the foot held in inversion and plantarflexion — using an interference screw or by suturing the tendon back onto itself over a button on the dorsal navicular surface. Proper tensioning is critical: too loose and the transfer fails to support the arch, too tight and it limits eversion.

Step 4: Spring ligament repair. The spring ligament (plantar calcaneonavicular ligament) is carefully assessed and repaired if attenuated. This structure provides essential static support to the talar head and medial arch. Imbrication or direct repair of the spring ligament augments the dynamic support provided by the FDL transfer and improves long-term stability of the reconstruction.

Medializing Calcaneal Osteotomy: The Critical Companion Procedure

The medializing calcaneal osteotomy is almost always performed alongside FDL transfer and is considered essential for long-term success. The concept is biomechanically powerful: by shifting the calcaneal tuberosity 10mm medially, the Achilles tendon insertion moves from a position that drives hindfoot valgus to one that supports inversion. This single osteotomy reduces the load on the transferred FDL by approximately 50%, dramatically improving the mechanical environment for tendon healing and long-term function.

The osteotomy is performed through a lateral oblique incision over the posterior calcaneal body. A complete transverse osteotomy is made perpendicular to the weightbearing surface, and the posterior fragment is shifted 8–10mm medially. The fragment is secured with one or two 6.5mm or 7.0mm partially threaded cannulated screws. The sural nerve runs in this area and must be carefully protected throughout the approach and fixation.

In cases with significant forefoot abduction (Stage IIB), additional procedures may be warranted. A lateral column lengthening through a calcaneal neck osteotomy (Evans procedure) or a Cotton medial cuneiform opening wedge osteotomy can address residual forefoot supinatus and abduction that the calcaneal slide alone cannot correct. The surgeon must carefully balance correction — under-correction leaves residual deformity while over-correction creates a painful rigid cavovarus foot.

Recovery Timeline and Weight-Bearing Progression

Recovery from FDL transfer with calcaneal osteotomy is a marathon, not a sprint. The rehabilitation protocol spans 3–6 months and requires patience, compliance, and progressive loading to achieve optimal outcomes. Understanding the timeline helps patients set realistic expectations and maintain motivation throughout the recovery process.

Weeks 0–2: Strict non-weight-bearing. The surgical leg is immobilized in a well-padded posterior splint with the foot in slight plantarflexion and inversion to protect the tendon transfer. Elevation above heart level is critical to minimize swelling. Ice therapy is applied around the splint margins. Pain management combines the popliteal nerve block (lasting 12–24 hours), oral analgesics, and anti-inflammatory medication. Patients use crutches or a knee scooter with absolutely no weight on the surgical foot.

Weeks 2–6: Non-weight-bearing in a cast. At the two-week mark, sutures are removed and the foot is placed in a short-leg fiberglass cast. The foot position is gradually brought to neutral from the initial plantarflexed position. Patients remain strictly non-weight-bearing. Gentle range of motion of the toes and knee is encouraged to prevent stiffness and maintain muscle tone. The calcaneal osteotomy typically shows early healing on radiographs by week 4–6.

Weeks 6–10: Protected weight-bearing in a CAM boot. Once radiographic healing of the osteotomy is confirmed, the cast is exchanged for a removable CAM walker boot. Weight-bearing progresses from 25% to 50% to 75% over these four weeks, guided by pain response and clinical examination. Physical therapy begins with gentle range of motion exercises, ankle alphabet movements, and progressive ankle strengthening. Scar massage and desensitization are started when the incisions are fully healed.

Weeks 10–14: Full weight-bearing and transition to shoes. Patients progress to full weight-bearing in the CAM boot, then gradually transition to supportive shoes with a custom orthotic. The orthotic is critical at this stage — it provides the external support that protects the healing transfer while the musculature rebuilds. Physical therapy intensifies with proprioception training, progressive resistance exercises, and gait retraining to normalize walking patterns.

Months 4–6: Return to full activity. Progressive return to higher-demand activities occurs between 4–6 months. Impact activities like running and jumping are typically the last to be cleared, usually around 6 months post-surgery. Some patients, particularly those over 60 or with bilateral disease, may require up to 12 months before achieving maximum recovery. Long-term use of supportive orthotics is recommended for all patients after FDL transfer to maintain surgical correction.

Post-Surgical Rehabilitation Protocol

Structured rehabilitation is the bridge between surgical correction and functional recovery. The physical therapy program is divided into phases that progressively challenge the reconstructed foot while respecting tissue healing timelines. At Balance Foot & Ankle, we coordinate closely with physical therapists who understand the specific demands of post-PTTD reconstruction rehabilitation.

Phase 1 (Weeks 6–10): Mobility restoration. Focus on regaining ankle dorsiflexion, plantarflexion, inversion, and eversion range of motion. Gentle manual therapy addresses scar adhesions and capsular restrictions. Towel stretches, seated ankle circles, and therapist-assisted mobilizations form the foundation. Intrinsic foot muscle activation begins with toe curls and short-foot exercises to rebuild the stabilizing musculature.

Phase 2 (Weeks 10–16): Strengthening foundation. Progressive resistance training targets the transferred FDL in its new role as an arch supporter. Theraband inversion exercises, standing heel raises (bilateral progressing to single-leg), and step-up activities build strength without excessive load. Balance training on stable surfaces progresses to unstable surfaces (foam pads, BOSU balls) to rebuild proprioception lost during immobilization. Aquatic therapy provides an excellent reduced-gravity environment for early walking and strengthening exercises.

Phase 3 (Weeks 16–24): Functional progression. Higher-level activities including lateral movements, uneven terrain walking, stair negotiation with reciprocal pattern, and sport-specific drills (if applicable) are introduced. Plyometric activities are carefully graded from double-leg to single-leg. Return-to-running programs follow a walk-jog-run progression with monitoring for symptoms. Patients are educated on permanent lifestyle modifications — ongoing orthotic wear, appropriate footwear selection, and maintenance exercise programs — that protect the surgical reconstruction long-term.

Long-Term Outcomes and Success Rates

The literature on FDL transfer with medializing calcaneal osteotomy demonstrates consistently favorable outcomes. Multiple studies with 5–15 year follow-up show patient satisfaction rates exceeding 90%, significant improvement in AOFAS hindfoot-ankle scores (typically from 40–50 preoperatively to 80–90 postoperatively), maintained radiographic correction of calcaneal pitch and talar coverage angles, and successful return to desired activity levels for the majority of patients.

The most important prognostic factor is proper patient selection — ensuring the deformity is truly flexible and the patient can comply with the extended recovery protocol. Patients with rigid deformity who undergo FDL transfer alone have significantly higher failure rates. Similarly, patients who return to full weight-bearing too quickly or skip physical therapy are at increased risk of transfer elongation and recurrent flatfoot. Age alone is not a contraindication — outcomes in properly selected patients over 65 are comparable to younger cohorts.

Potential Complications and Risk Management

Like all surgical procedures, FDL transfer with calcaneal osteotomy carries risks that must be discussed thoroughly during preoperative counseling. Understanding these complications helps patients make informed decisions and recognize warning signs during recovery that warrant immediate medical attention.

Wound healing complications occur in approximately 5–8% of cases and are more common in patients with diabetes, peripheral vascular disease, or tobacco use. The medial incision is particularly vulnerable because the skin over the medial ankle has limited blood supply. Meticulous soft tissue handling, layered closure, and strict elevation postoperatively minimize this risk. Smoking cessation for at least 6 weeks before and after surgery is strongly recommended.

Sural nerve injury is the most common nerve complication, occurring in 5–10% of cases from the lateral calcaneal osteotomy approach. Symptoms range from temporary numbness along the lateral foot border to chronic neuropathic pain. Careful identification and protection of the sural nerve during the lateral approach reduces this risk. Most sural nerve injuries are neurapraxic and resolve spontaneously within 3–6 months.

Recurrent flatfoot occurs in approximately 5–10% of patients at long-term follow-up and may result from transfer elongation, progressive spring ligament insufficiency, or inadequate initial correction. Patients with higher BMI, bilateral disease, or inflammatory conditions are at greater risk. Lifetime orthotic use and maintenance of healthy body weight help prevent recurrence. When recurrence does occur, revision surgery or conversion to arthrodesis may be necessary.

Hardware prominence from the calcaneal osteotomy screw is reported in 10–15% of patients, particularly in thin individuals. The screw head can become palpable or irritating in shoes. Symptomatic hardware can be removed after the osteotomy has fully healed (typically after 12 months) through a small outpatient procedure.

Foot Care Products for PTT Repair Recovery

Recovery from FDL transfer requires consistent support and pain management. These podiatrist-recommended products address the specific challenges of post-surgical rehabilitation and long-term arch maintenance after PTTD reconstruction.

PowerStep Orthotic Insoles — Post-Surgical Arch Support

PowerStep Pinnacle orthotic insoles provide the structured arch support that is essential after FDL transfer. The semi-rigid shell with medical-grade arch control maintains the surgical correction while distributing weight away from the healing reconstruction. During the transition from CAM boot to regular shoes (weeks 10–14), PowerStep insoles bridge the gap between full immobilization and custom orthotics. The antimicrobial top cover and dual-layer cushioning make them comfortable for the extended wear required during rehabilitation. Many of our post-PTTD patients use PowerStep as their daily orthotic for long-term arch maintenance between custom orthotic replacements.

Doctor Hoy’s Natural Pain Relief Gel — Post-Operative Pain Management

Doctor Hoy’s Natural Pain Relief Gel is our preferred topical analgesic for post-surgical pain and inflammation management after FDL transfer. The clean, natural arnica and menthol formula provides effective pain relief without the chemical concerns of traditional topical analgesics. During the rehabilitation phases, Doctor Hoy’s is particularly valuable — applied before physical therapy sessions, it reduces pain enough to allow productive stretching and strengthening exercises. The non-greasy formula absorbs quickly and works well under compression garments without causing skin irritation. For patients managing the significant swelling common after calcaneal osteotomy, Doctor Hoy’s cooling effect provides welcome relief during the challenging first weeks of recovery.

DASS Compression Socks — Edema Control During Recovery

DASS graduated compression socks are essential for managing the prolonged swelling that accompanies FDL transfer and calcaneal osteotomy recovery. Post-surgical edema is one of the most persistent challenges — many patients experience significant swelling for 3–6 months after surgery, and some degree of swelling can persist up to 12 months. DASS 20–30 mmHg graduated compression improves venous return and lymphatic drainage, reducing swelling that otherwise causes pain, stiffness, and delayed healing. We recommend patients begin wearing DASS compression as soon as the surgical wounds have healed (typically week 2–3), continuing daily use throughout the rehabilitation period and beyond if needed.

🎯 Complete Recovery Kit: Our PTTD reconstruction patients achieve the best outcomes with all three Foundation Wellness products working together. PowerStep insoles maintain surgical correction and arch support, Doctor Hoy’s gel manages pain during the intensive rehabilitation phases, and DASS compression controls the persistent post-surgical edema. This combination addresses the three main recovery challenges — structural support, pain management, and swelling control — that determine long-term surgical success.

🔑 Most Common Mistake: The biggest mistake patients make after FDL transfer is rushing the recovery timeline. Returning to weight-bearing too early — even by a few weeks — can cause the tendon transfer to stretch and elongate, resulting in recurrent flatfoot that may require revision surgery. Every week of non-weight-bearing matters. Follow the prescribed timeline precisely, use your compression and orthotics consistently, and resist the temptation to progress faster than your surgeon recommends.

⚠️ Warning Signs After Surgery — Seek Immediate Care: Contact your surgeon immediately if you experience increasing pain not controlled by medication (especially after the first week), fever above 101°F, wound drainage that is cloudy, colored, or foul-smelling, sudden calf pain or swelling (possible deep vein thrombosis), numbness or tingling that worsens rather than improves, or toes that become dusky, cold, or fail to blanch when pressed. These may indicate infection, blood clot, or neurovascular compromise that requires urgent intervention.

Watch Dr. Tom Explain Foot Care Products for Recovery

https://www.youtube.com/watch?v=A11FFjCXAX4

Frequently Asked Questions About FDL Transfer

How long does FDL transfer surgery take?

The complete procedure — including FDL tendon transfer, medializing calcaneal osteotomy, and spring ligament repair — typically takes 2–3 hours. If additional procedures like lateral column lengthening or Cotton osteotomy are needed, the surgery may extend to 3–4 hours. Most patients go home the same day with a nerve block providing initial pain control.

Will I lose toe function after FDL harvest?

Most patients experience minimal to no functional loss in the lesser toes after FDL harvest. The flexor hallucis longus tendon has interconnections through the knot of Henry that partially compensate for FDL loss. You may notice slightly reduced ability to grip with your lesser toes when barefoot, but this rarely affects walking, running, or daily activities. The side-to-side tenodesis performed during surgery further preserves toe flexion.

How long before I can drive after FDL transfer?

If surgery is on the left foot and you drive an automatic transmission, you may be cleared to drive as early as 2–3 weeks, provided you are off narcotic pain medication and can safely operate the pedals with your non-surgical foot. For right foot surgery, driving is typically restricted until you are fully weight-bearing and out of the CAM boot — usually 10–14 weeks. Always follow your surgeon’s specific guidance, as premature driving puts both you and others at risk.

Can PTTD come back after FDL transfer?

Recurrence of flatfoot deformity occurs in approximately 5–10% of patients after FDL transfer with calcaneal osteotomy. Risk factors for recurrence include elevated BMI, bilateral disease, inflammatory conditions like rheumatoid arthritis, non-compliance with postoperative orthotic use, and premature return to high-impact activities. Lifetime orthotic wear and maintenance of healthy body weight are the most important modifiable factors in preventing recurrence.

Is FDL transfer covered by insurance?

Yes, FDL tendon transfer with calcaneal osteotomy for Stage II PTTD is considered a medically necessary reconstructive procedure and is covered by most health insurance plans, including Medicare. Pre-authorization is typically required. Your surgeon’s office will submit the appropriate CPT codes (28300 for calcaneal osteotomy, 27691 for tendon transfer) along with supporting documentation including MRI findings and evidence of failed conservative treatment.

Sources

1. Myerson MS, et al. “Posterior tibial tendon dysfunction: Its association with seronegative inflammatory disease.” Foot & Ankle International. 1996;17(10):567-572.
2. Haddad SL, et al. “Results of flexor digitorum longus transfer to the navicular for posterior tibial tendon dysfunction.” Foot & Ankle International. 2005;26(10):793-802.
3. Guyton GP, et al. “An analysis of calcaneal osteotomies: A review of 100 consecutive cases.” Foot & Ankle International. 2001;22(10):775-778.
4. Bluman EM, et al. “Stage IV posterior tibial tendon insufficiency.” Foot & Ankle Clinics. 2007;12(2):341-362.
5. Vulcano E, et al. “Posterior tibial tendon dysfunction: Current concepts review.” Foot & Ankle International. 2016;37(3):57-66.

Ready to Discuss Your PTTD Treatment Options?

Dr. Biernacki at Balance Foot & Ankle specializes in posterior tibial tendon reconstruction and flatfoot correction. If conservative treatment has not improved your PTTD symptoms, a thorough evaluation can determine whether FDL transfer is right for you.

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Posterior Tibial Tendon Surgery in Michigan

Stage II PTTD that doesn’t respond to bracing and physical therapy may benefit from FDL tendon transfer and calcaneal osteotomy. Our board-certified podiatric surgeons perform these reconstructive procedures at our Howell and Bloomfield Hills offices.

Learn About Flatfoot Reconstruction | Book Your Appointment | Call (810) 206-1402

Clinical References

1. Myerson MS. Adult acquired flatfoot deformity: treatment of dysfunction of the posterior tibial tendon. Instr Course Lect. 1997;46:393-405.
2. Haddad SL, et al. Results of flexor digitorum longus transfer to the navicular for adult-acquired flatfoot deformity. Foot Ankle Int. 2003;24(4):354-359.
3. Bluman EM, Title CI, Myerson MS. Posterior tibial tendon rupture: a refined classification system. Foot Ankle Clin. 2007;12(2):233-249. doi:10.1016/j.fcl.2007.03.003