Flexor Hallucis Longus (FHL) tendinitis is an overuse injury that causes inflammation, irritation, or degeneration of the FHL tendon. It most commonly affects dancers, runners, and athletes who repeatedly push off the big toe, leading to pain and stiffness behind the ankle or along the inside of the foot. The FHL tendon plays a vital role in foot mechanics, and injury to this structure can severely limit mobility and performance if left untreated.
How Common It Is and Who Gets It? (Epidemiology)
FHL tendinitis is relatively uncommon but frequently seen in ballet dancers, soccer players, runners, and individuals involved in jumping or pushing-off sports. It is sometimes referred to as “dancer’s tendinitis” due to its high prevalence in ballet dancers performing movements like pointe and relevé. It typically affects adults between 20 and 40 years of age and occurs more often in individuals with flat feet or hypermobile joints.
Why It Happens – Causes (Etiology and Pathophysiology)
The FHL tendon originates from the posterior leg (fibula) and travels through a narrow fibro-osseous tunnel behind the ankle before inserting at the base of the big toe’s distal phalanx. Because of its long course and narrow passages, it is prone to friction and compression.
- Repetitive stress: Continuous plantarflexion (pointing the toes downward) increases tension on the tendon.
- Overuse: Common in activities like running, ballet, or gymnastics.
- Biomechanical abnormalities: Flat feet, tight calf muscles, or excessive pronation may increase strain.
- Trauma or entrapment: Thickening or adhesions within the tendon sheath can limit tendon glide and cause pain.
Chronic inflammation can lead to stenosing tenosynovitis, where the tendon sheath narrows, restricting tendon motion and causing locking or snapping sensations.
How the Body Part Normally Works? (Relevant Anatomy)
The FHL muscle lies deep in the posterior compartment of the leg and helps flex the big toe downward and assist with ankle plantarflexion. It stabilizes the arch during walking and running and provides push-off strength when propelling forward. It runs through a groove behind the talus and passes under the foot at the “knot of Henry,” where it crosses the flexor digitorum longus tendon. This pathway makes it susceptible to entrapment or irritation, especially in athletes with repetitive foot and ankle motion.
What You Might Feel – Symptoms (Clinical Presentation)
- Pain and tenderness along the inner (posteromedial) side of the ankle.
- Pain during push-off, toe flexion, or pointing the toes downward.
- Swelling around the back or inside of the ankle.
- Stiffness or snapping of the tendon when moving the big toe.
- Weakness in toe flexion or an inability to stand on tiptoe.
The pain often worsens with activities such as running, dancing, or climbing stairs and may radiate along the arch or under the heel.
How Doctors Find the Problem? (Diagnosis and Imaging)
Diagnosis is primarily clinical, supported by imaging when necessary.
- Physical examination: Tenderness along the FHL tendon course. Pain reproduced with the FHL stretch test (dorsiflexion of the ankle and big toe).
- Ultrasound: Demonstrates tendon inflammation, sheath thickening, or adhesions.
- MRI: Confirms tenosynovitis, partial tearing, or entrapment in the fibro-osseous tunnel.
- Differential diagnosis: Must rule out posterior ankle impingement, plantar fasciitis, tarsal tunnel syndrome, or sesamoiditis.
Classification
FHL tendinitis can be divided by stage and severity:
- Stage I (Mild) – Inflammation without structural damage; pain only with activity.
- Stage II (Moderate) – Thickening or stenosis of the tendon sheath causing restricted motion.
- Stage III (Severe) – Partial tearing, adhesions, or nodular enlargement of the tendon causing mechanical locking.
Other Problems That Can Feel Similar (Differential Diagnosis)
- Posterior ankle impingement syndrome
- Tarsal tunnel syndrome
- Plantar fasciitis
- Sesamoiditis or stress fractures of the foot
- Tibialis posterior tendinitis
Treatment Options
Non-Surgical Care
Most cases of FHL tendinitis respond well to conservative treatment.
- Rest and activity modification: Reduce repetitive plantarflexion or toe push-off activities.
- NSAIDs: Reduce pain and inflammation.
- Physical therapy: Gentle stretching and strengthening exercises for the calf and FHL tendon.
- Orthotics or heel lifts: Help offload stress from the tendon.
- Immobilization: Use of a walking boot or brace for several weeks in severe inflammation.
- Corticosteroid injections: Rarely used due to the risk of tendon weakening.
Surgical Care
Surgery is reserved for persistent cases or mechanical stenosis.
- FHL Tenolysis (Tendon Release): Involves releasing adhesions and freeing the tendon for smoother gliding.
- FHL Tendon Transfer: In cases with significant degeneration or Achilles pathology, the FHL tendon can be transferred to assist the Achilles, providing strong plantarflexion while maintaining good function of the big toe.
Post-surgical rehabilitation focuses on gentle range of motion, progressive strengthening, and gradual return to activity.
Recovery and What to Expect After Treatment
Most patients respond to conservative therapy within 6–8 weeks. After surgery, recovery typically takes 8–12 weeks, with return to full activity after 3 months. Structured rehabilitation and avoidance of overuse are key to successful recovery.
Possible Risks or Side Effects (Complications)
- Persistent pain or recurrence if underlying mechanics are not corrected.
- Stiffness and scar tissue formation.
- Nerve irritation or weakness of the big toe after surgery.
- Rarely, tendon rupture if corticosteroids are used excessively.
Long-Term Outlook (Prognosis)
The prognosis for FHL tendinitis is excellent with early diagnosis and treatment. Most patients regain full function without chronic pain. Dancers and athletes can return to performance levels after proper rehabilitation. Untreated cases, however, may lead to chronic tendinopathy or tendon rupture.
Out-of-Pocket Costs
Medicare
CPT Code 28200 – Repair, Tendon, Flexor, Foot (e.g., FHL Tenolysis or Repair): $113.23
CPT Code 27691 – Transfer or Transplant of Single Tendon, Leg (e.g., FHL Tendon Transfer to Achilles): $175.25
Medicare Part B covers 80% of the approved cost for these procedures once your annual deductible has been met, leaving you responsible for the remaining 20%. Supplemental Insurance plans such as Medigap, AARP, or Blue Cross Blue Shield usually cover that 20%, minimizing or eliminating out-of-pocket expenses for Medicare-approved surgeries. These supplemental plans are designed to work alongside Medicare to fill any coverage gaps.
If you have Secondary Insurance, such as TRICARE, an Employer-Based Plan, or Veterans Health Administration coverage, it acts as a secondary payer. These plans often cover any remaining coinsurance or deductible amounts, which typically range from $100 to $300 depending on your plan’s terms and provider network.
Workers’ Compensation
If your FHL tendinitis developed or worsened due to a work-related injury, Workers’ Compensation will cover all medical expenses related to the procedure, including surgery, rehabilitation, and postoperative care. You will not have any out-of-pocket expenses, as the employer’s insurance carrier will pay all approved costs directly.
No-Fault Insurance
If your FHL tendinitis or related injury is due to an automobile accident, No-Fault Insurance will typically cover the full cost of treatment, including surgery and recovery. The only potential out-of-pocket cost may be a small deductible or co-payment, depending on your insurance policy.
Example
Rachel Simmons developed Flexor Hallucis Longus (FHL) tendinitis causing chronic ankle pain and stiffness. She underwent FHL tendon repair (CPT 28200) followed by FHL tendon transfer (CPT 27691). Her estimated Medicare out-of-pocket cost for the tendon transfer was $175.25. Since Rachel had supplemental insurance through Blue Cross Blue Shield, her remaining balance was fully covered, leaving her with no out-of-pocket expenses for the surgery.
Frequently Asked Questions (FAQ)
Q. What is Flexor Hallucis Longus (FHL) Tendinitis?
A. FHL tendinitis is inflammation of the tendon that flexes the big toe, often caused by overuse or repetitive stress, especially in athletes and dancers.
Q. What causes FHL tendinitis?
A. FHL tendinitis is commonly caused by repetitive ankle and toe motion, especially in activities like ballet, running, or sports that require frequent toe-off movements.
Q. What are the symptoms of FHL tendinitis?
A. Symptoms include pain behind the ankle, swelling, stiffness, tenderness along the inner side of the ankle, and pain that worsens with activity.
Q. How is FHL tendinitis diagnosed?
A. Diagnosis is typically based on clinical examination and patient history. Imaging such as MRI or ultrasound may be used to confirm the diagnosis and rule out other conditions.
Q. What non-surgical treatments are available for FHL tendinitis?
A. Treatments include rest, ice, anti-inflammatory medications, physical therapy, activity modification, orthotics, and sometimes immobilization.
Q. When is surgery needed for FHL tendinitis?
A. Surgery may be considered if non-operative treatments fail to relieve symptoms or if there is significant tendon damage or tearing.
Q. What does surgery for FHL tendinitis involve?
A. Surgery typically involves removing inflamed tissue, releasing the tendon sheath, or repairing the tendon if it is torn.
Q. What is the recovery time after FHL tendon surgery?
A. Recovery varies but generally includes a period of immobilization followed by physical therapy, with return to full activity taking several months.
Q. Can FHL tendinitis be prevented?
A. Prevention strategies include proper stretching, strengthening exercises, avoiding overuse, and using appropriate footwear for activity.
Q. Who is most at risk for FHL tendinitis?
A. Athletes, especially ballet dancers and runners, are at higher risk due to repetitive toe flexion and ankle movements.
Summary and Takeaway
Flexor Hallucis Longus tendinitis is an overuse injury causing pain and inflammation along the inner ankle due to repetitive stress on the big toe tendon. It is common in dancers and athletes but can affect anyone with poor foot mechanics or overuse. Early recognition and conservative management usually lead to full recovery. Surgical release provides excellent outcomes for refractory cases, restoring mobility and performance.
Clinical Insight & Recent Findings
A recent study found that surgical debridement of the Achilles tendon with FHL tendon transfer significantly improved pain, function, and strength in older, overweight patients with chronic Achilles tendinosis. Hallux weakness post-surgery had minimal functional impact, supporting FHL tendon transfer as a reliable option for chronic cases requiring surgical intervention.
Who Performs This Treatment? (Specialists and Team Involved)
Treatment is provided by orthopedic foot and ankle surgeons or podiatric surgeons, often with physical therapists assisting in rehabilitation.
When to See a Specialist?
Consult a specialist if pain persists for more than a few weeks despite rest or if pain worsens with activity, affecting walking or sports performance.
When to Go to the Emergency Room?
Go to the ER if pain is severe, associated with swelling, warmth, redness, or if you cannot bear weight on the affected foot.
What Recovery Really Looks Like?
Recovery includes rest, progressive therapy, and gradual return to normal activity. After surgery, weight-bearing typically resumes after 6 weeks, followed by strengthening exercises to restore function.
What Happens If You Ignore It?
Ignoring FHL tendinitis can result in chronic pain, restricted motion, tendon scarring, or rupture, potentially requiring extensive surgical correction.
How to Prevent It?
Maintain calf flexibility, strengthen foot and ankle muscles, wear supportive shoes, and avoid repetitive overuse or sudden increases in activity intensity.
Nutrition and Bone or Joint Health
A diet rich in omega-3 fatty acids, calcium, and vitamin D supports tendon healing and bone strength. Staying hydrated and avoiding smoking enhances tissue recovery.
Activity and Lifestyle Modifications
Gradually increase training intensity, stretch before activity, and cross-train to reduce repetitive strain. For dancers and athletes, proper technique and regular rest are essential to prevent recurrence.
Dr. Mo Athar
