Posterior Ankle Impingement and Os Trigonum: Endoscopic Excision Technique and Outcomes

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

Posterior ankle impingement syndrome — pain at the posterior aspect of the ankle from compression of osseous or soft tissue structures between the tibia and calcaneus during forced plantarflexion — most commonly involves the os trigonum (an accessory ossicle representing a non-united lateral process of the posterior talus, present in 3–14% of the population) or a hypertrophied Stieda’s process (elongated lateral tubercle of the posterior talus). The syndrome is endemic in ballet dancers, soccer players (from kicking with a plantarflexed ankle), and gymnasts, and endoscopic posterior ankle arthroscopy has become the preferred surgical approach — providing equivalent outcomes to open surgery with significantly faster recovery and fewer wound complications.

Anatomy, Diagnosis, and Conservative Management

Os trigonum anatomy: the posterior talar process normally unites with the talus during skeletal development (ages 8–11); failure of fusion leaves a separate ossicle attached to the posterior talus by a synchondrosis; during forced plantarflexion, the os trigonum is compressed between the posterior tibia and the superior calcaneal surface; the FHL tendon courses immediately medial to the os trigonum and is frequently involved (concurrent FHL tenosynovitis). Clinical diagnosis: posterior ankle pain with forced plantarflexion (equinus position) — the pathognomonic provocative maneuver; point tenderness directly posterior to the fibula and lateral to the Achilles tendon; the ‘nutcracker test’ — passive forced plantarflexion reproduces the pain; MRI confirms synchondrosis edema (bone marrow edema pattern adjacent to the os trigonum on T2), FHL tenosynovitis, and the absence of other posterior ankle pathology. Conservative management: activity modification; cortisone injection into the os trigonum synchondrosis under ultrasound guidance (60–70% short-term improvement in non-ballet patients); physical therapy; 3–6 months appropriate trial before surgical consideration.

Endoscopic Posterior Ankle Arthroscopy (EPAA) Technique

Patient positioning: prone, with the ankle at the edge of the table to allow plantarflexion; two posterior portals — posteromedial (medial to the Achilles tendon) and posterolateral (lateral to the Achilles tendon), both at the level of the posterior ankle joint. Anatomical orientation: the FHL tendon is the critical medial landmark — all instrumentation stays lateral to the FHL to protect the medial neurovascular structures. Procedure: posterior ankle joint visualization; identification of the os trigonum or Stieda’s process; blunt dissection of the synchondrosis between the os trigonum and talus; excision of the os trigonum with an arthroscopic shaver and punch; FHL tendon sheath decompression (invariably performed concurrently). Recovery: weight-bearing as tolerated immediately postoperatively; ballet and sport-specific rehabilitation beginning at 2 weeks; return to full dance or sport at 6–8 weeks (vs. 12–16 weeks with open surgery). Outcomes: 88–94% good-excellent results; 95% return to prior sport level; significantly faster return to activity than open posterior ankle approach. Dr. Biernacki at Balance Foot & Ankle performs posterior ankle arthroscopy and os trigonum excision at our Bloomfield Hills and Howell offices. Call (810) 206-1402.

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Frequently Asked Questions

How do I know if I sprained or broke my ankle?

Both cause pain, swelling, and difficulty walking. Key differences: fractures often cause more immediate severe pain, tenderness directly over bone (not just ligament), and inability to bear any weight. X-rays and the Ottawa Ankle Rules help determine if imaging is needed.

How long does an ankle sprain take to heal?

Grade I (mild): 1–2 weeks. Grade II (moderate): 3–6 weeks. Grade III (complete tear): 2–3 months. Chronic instability from improperly treated sprains can persist and may require surgery.

What is the best treatment for a sprained ankle?

RICE protocol (Rest, Ice, Compression, Elevation) for the first 48–72 hours, followed by protected weight-bearing as tolerated. Physical therapy rehabilitation is critical for high-grade sprains to restore strength and proprioception and prevent chronic instability.

Need Treatment at Balance Foot & Ankle?

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

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.

In-Office Treatment at Balance Foot & Ankle

If home treatment isn’t providing relief for your foot and ankle injuries, our podiatry team at Balance Foot & Ankle can help with same-day evaluations and advanced in-office care.