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 Township, 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 Township 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 Township 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

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.