Medically Reviewed | Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle, Michigan
Quick Answer:
Quick Answer: Posterior ankle impingement occurs when structures at the back of the ankle — including the os trigonum (an accessory bone behind the talus present in ~10% of people), the posterior talar process, or thickened posterior capsule — are compressed during plantarflexion. It is the classic ‘ballet dancer’s heel’ — pain at the back of the ankle with pointe or demi-pointe position. It also occurs in soccer players, downhill runners, and anyone requiring extreme ankle plantarflexion. Dr. Biernacki treats posterior impingement with targeted injection and, when necessary, endoscopic os trigonum excision — a minimally invasive procedure with rapid recovery.
What Is Posterior Ankle Impingement?
The posterior ankle contains several structures that can become impinged with maximum plantarflexion (pointing the foot down). The os trigonum — a small accessory ossicle posterior to the talus, found in approximately 10% of the population — can be compressed between the talus and calcaneus during plantarflexion. The posterior talar process (Stieda’s process), the posterior ankle capsule, the flexor hallucis longus tendon sheath, and post-traumatic fibrotic bands can all contribute to posterior impingement syndrome. The result is a deep, posterior heel pain specifically reproduced with forced plantarflexion.
Who Gets Posterior Ankle Impingement?
Ballet dancers are the archetypal patient — the en pointe position requires extreme plantarflexion that directly loads the posterior ankle. Professional and recreational dancers with recurrent posterior heel pain after dancing are among the most common presentations. Soccer players develop posterior impingement from the kicking motion (rapid forced plantarflexion on the plant foot). Downhill runners, gymnasts, and athletes requiring maximum ankle extension are also at risk. An acute os trigonum fracture can occur from a single forced plantarflexion event.
Diagnosis: MRI and Clinical Testing
The clinical hallmark is the plantarflexion stress test — forcefully plantarflexing the ankle reproduces posterior heel pain specifically. Lateral ankle X-ray identifies the os trigonum or elongated posterior talar process. MRI demonstrates bone marrow edema within the os trigonum (indicating active stress) and any associated FHL tendon abnormality. Ultrasound-guided injection of local anesthetic into the posterior ankle confirming immediate pain relief is both diagnostic and briefly therapeutic.
Conservative Treatment
Conservative management for posterior impingement includes activity modification (limiting extreme plantarflexion), corticosteroid injection into the posterior ankle under ultrasound guidance, physical therapy for posterior ankle range of motion and eccentric calf strengthening, and in dancers, modification of technique. A posterior ankle injection can provide weeks to months of relief and may be repeated. For professional athletes or dancers who cannot curtail activity, surgical excision may be indicated more readily than in recreational patients.
Endoscopic Os Trigonum Excision
When conservative care fails, endoscopic excision of the os trigonum is a highly effective minimally invasive procedure. Using two small portals at the back of the ankle, Dr. Biernacki removes the os trigonum and any associated posterior osteophytes under camera guidance. The FHL tendon sheath is decompressed if involved. The procedure takes 30–45 minutes under sedation, with weight-bearing beginning immediately. Return to dance or sport typically occurs at 6–8 weeks. Published success rates exceed 90% with significantly lower complication rates than open posterior approaches.
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✅ Pros / Benefits
- Endoscopic excision is minimally invasive with 90%+ success rate and rapid recovery.
- Immediate weight-bearing after surgery — return to sport in 6–8 weeks.
- Targeted posterior ankle injection provides diagnosis confirmation and temporary relief.
- FHL tendon decompression can be performed simultaneously through same portals.
❌ Cons / Risks
- Os trigonum is only symptomatic in ~10% of those who have one — correct diagnosis before surgery.
- Small risk of sural nerve or small saphenous vein injury with posterior portals.
- Conservative management may need to be repeated over months in professional dancers.
Dr. Tom Biernacki’s Recommendation
Posterior ankle impingement is the diagnosis every dancer finally hears after years of being told ‘it’s just posterior ankle tendinitis.’ The os trigonum lights up on MRI with bone marrow edema and suddenly everything makes sense. Endoscopic excision through two tiny holes at the back of the ankle — and dancers are back in the studio in 6–8 weeks. It’s one of the most rewarding procedures I perform.
— Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle
Frequently Asked Questions
Is an os trigonum always painful?
No — an os trigonum is an incidental finding in approximately 10% of the population, and most people with one never have symptoms. It becomes symptomatic when subjected to repetitive compressive loading during extreme plantarflexion, causing bone marrow edema and posterior impingement.
Can posterior ankle impingement heal without surgery?
Many patients manage posterior impingement successfully with injection therapy, activity modification, and rehabilitation. Professional dancers and athletes who cannot adequately limit plantarflexion activity often progress to surgical excision sooner.
How long is recovery after endoscopic os trigonum removal?
Most patients bear weight immediately in a surgical shoe. Return to regular footwear at 2–3 weeks. Return to dance or high-level sport at 6–8 weeks. Most patients describe the recovery as significantly easier than anticipated.
Does everyone with posterior heel pain have os trigonum syndrome?
No — posterior heel pain has multiple causes including insertional Achilles tendinopathy, Haglund’s deformity, retrocalcaneal bursitis, and FHL tendinopathy. Clinical exam with the plantarflexion stress test and MRI differentiate these diagnoses accurately.
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Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.
- Diagnosis and Treatment of Plantar Fasciitis (PubMed / AAFP)
- Heel Pain (APMA)
- Hallux Valgus (Bunions): Evaluation and Management (PubMed)
- Bunions (Mayo Clinic)