Posterior Ankle Impingement: Os Trigonum and FHL Causes,

Posterior ankle impingement syndrome — pain at the back of the ankle provoked by plantarflexion — is a common cause of posterior ankle pain in ballet dancers, gymnasts, soccer players, and any athlete performing repetitive plantarflexion activities. Two anatomic structures are responsible for the majority of posterior impingement cases: the os trigonum (or prominent posterior talar process/Stieda process) and the flexor hallucis longus (FHL) tendon. Both may coexist and must be assessed concurrently.

Os Trigonum Impingement

The os trigonum is an accessory ossicle posterior to the talus, present as a normal variant in approximately 7–14% of the population. In plantarflexion, the posterior ankle space narrows and the os trigonum is compressed between the posterior tibia and calcaneus — producing the bony impingement. In the ballet dancer, en pointe position represents the most extreme provocative position, explaining the high prevalence in this population. The diagnosis is confirmed by: posterior ankle tenderness on direct palpation posterior to the peroneal tendons; pain with passive forced plantarflexion; posterior ankle pain provoked by a diagnostic lidocaine injection into the os trigonum region. Lateral ankle radiograph in maximum plantarflexion demonstrates the os trigonum or prominent posterior talar process. MRI shows bone marrow edema in the os trigonum and/or fluid at the synchondrosis between the os and the talar body.

FHL Tendinopathy and Impingement

The FHL tendon passes through the fibrosseous tunnel between the medial and lateral talar tubercles (the knot of Henry) and through the sustentaculum tali — the narrowest points where the tendon is vulnerable to stenosing tenosynovitis and impingement. FHL impingement presents as posterior ankle pain provoked by great toe dorsiflexion under load, a triggering sensation with toe dorsiflexion, and tenderness posterior to the medial malleolus along the FHL course. Ultrasound with dynamic assessment of FHL gliding is the primary diagnostic tool.

Treatment

Conservative management: activity modification, corticosteroid injection under ultrasound guidance into the posterior ankle joint or os trigonum region, and physical therapy. Surgical treatment for refractory cases involves posterior ankle arthroscopy with os trigonum excision, posterior talar process excision, or FHL release through the fibrosseous tunnel — all achievable with a two-portal posterior arthroscopic approach that avoids the scarring, sural nerve risk, and recovery of open approaches. Dr. Biernacki at Balance Foot & Ankle evaluates posterior ankle pain with clinical examination and imaging, and performs posterior ankle arthroscopy for appropriate patients. Call (810) 206-1402 at our Bloomfield Hills or Howell office.

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When to See a Podiatrist

Many foot conditions can be managed conservatively at home, but some require professional evaluation. See a podiatrist promptly if you experience:

• Pain that persists for more than 2 weeks despite rest
• Swelling, redness, or warmth that isn’t improving
• Numbness, tingling, or burning in the feet
• A wound or sore that is not healing within 2 weeks
• Any foot concern if you have diabetes or poor circulation
• Nail changes that suggest fungal infection or other problems

At Balance Foot & Ankle, our three board-certified podiatrists — Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin — provide comprehensive foot and ankle care at our Howell and Bloomfield Hills offices. Most insurance plans are accepted.

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Board-certified podiatrists Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin see patients daily at our Howell and Bloomfield Township, MI offices.

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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-day and next-day appointments at both our Howell and Bloomfield Hills 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.

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

What is Foot pain?

Foot pain is a common foot/ankle condition that affects mobility and quality of life. Understanding the underlying cause is the first step in successful treatment. Our podiatrists at Balance Foot & Ankle perform a hands-on biomechanical exam, review your activity history, and use diagnostic imaging when appropriate to identify the root cause—not just treat the symptom. Many patients have been told to “rest and ice” without a deeper diagnostic workup; our approach is different.

Symptoms and warning signs

Common signs of foot pain include pain that worsens with activity, morning stiffness, swelling, tenderness when palpated, and difficulty bearing weight. If you experience sudden severe pain, inability to walk, visible deformity, numbness or color change, contact our office the same day or visit urgent care—these can signal a more serious injury such as a fracture, tendon rupture, or vascular compromise. Diabetics with any foot wound should seek same-day care.

Conservative treatment options

Most cases of foot pain respond to non-surgical care: structured rest, supportive footwear changes, custom orthotics, targeted stretching and strengthening protocols, anti-inflammatory medications when medically appropriate, and in-office procedures such as ultrasound-guided injections. We also offer advanced therapies including MLS laser therapy, EPAT/shockwave, regenerative injections, and image-guided procedures. Treatment is sequenced from least invasive to most invasive, and we explain the rationale at every step.

When is surgery considered?

Surgery is reserved for cases that fail 3-6 months of well-structured conservative care, when there is structural pathology (severe deformity, complete tear, advanced arthritis), or when imaging shows damage that will not heal without intervention. Our surgeons have performed 3,000+ foot and ankle procedures and prioritize minimally-invasive techniques whenever appropriate. We discuss recovery timelines, return-to-activity milestones, and realistic outcome expectations before any procedure is scheduled.

Recovery timeline and prevention

Recovery from foot pain varies based on severity and chosen treatment path. Conservative cases often improve within 4-8 weeks with consistent adherence to the protocol. Post-procedural recovery may range from a few days (in-office procedures) to several months (reconstructive surgery). Long-term prevention involves footwear assessment, activity modification, structured strengthening, and regular check-ins with your podiatrist if you have a history of recurrence. We provide written home-exercise plans and digital follow-up support.