Os Trigonum in Dancers 2026: Posterior Ankle Pain | DPM

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

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Posterior ankle impingement syndrome — and its most common structural cause, the os trigonum — is a frequently missed diagnosis in dancers, gymnasts, soccer players, and athletes who work in maximal plantarflexion (pointed foot position). The characteristic deep posterior ankle pain triggered specifically by full foot plantarflexion is pathognomonic when the clinical picture is correct, yet it is routinely misdiagnosed as ankle sprain, Achilles tendinopathy, or non-specific ankle pain. The distinction matters because the treatment — including surgical excision of the os trigonum when indicated — is highly specific and predictably effective.

What Is the Os Trigonum?

The os trigonum is an accessory ossicle (an extra bone) situated posterior to the talus, present in approximately 7–14% of the population. It represents a secondary ossification center of the lateral talar tubercle that failed to fuse with the talus during skeletal development — normally this occurs between ages 7 and 13. When present, the os trigonum may remain asymptomatic throughout life, or it may become symptomatic when activities compress it between the calcaneus and the posterior tibia during forced plantarflexion.

Even without an os trigonum, the posterolateral talar process itself can be elongated (Stieda process), producing the same impingement syndrome from bony impingement of the normal talus.

Mechanism of Injury

During full plantarflexion (the en pointe position in ballet, the instep kick in soccer, the dismount landing in gymnastics), the talus rotates into the tibiotalar joint and the posterior talar process — or the os trigonum — is compressed between the posterior tibia above and the calcaneus below. Repetitive or forceful compression inflames the synchondrosis (the fibrocartilaginous junction between the os trigonum and talus), the surrounding soft tissue, the flexor hallucis longus (FHL) tendon sheath (which runs directly adjacent), and the posterior ankle capsule.

Symptoms

• Deep posterior ankle pain triggered specifically by forced plantarflexion — the hallmark symptom
• Pain with relévé (rising on tiptoe), en pointe position, or instep ball kicks in soccer
• Tenderness to deep palpation directly posterior to the lateral malleolus, between the peroneal tendons and Achilles tendon
• The “nutcracker test” (forced passive plantarflexion by the examiner) reproduces the pain — a highly specific diagnostic maneuver
• Occasionally associated FHL tendinopathy: catching or triggering of the big toe with ankle motion (ballet dancer’s “clicking ankle”)

Diagnosis

Lateral ankle X-ray identifies the os trigonum in most cases. MRI provides the most complete assessment — demonstrating bone marrow edema within the os trigonum (indicating acute impingement), FHL tendon sheath fluid, posterior capsular thickening, and the relationship of the os trigonum to adjacent structures. Diagnostic ultrasound visualizes FHL tendinopathy and bursal fluid in real time. An ultrasound-guided local anesthetic injection directly at the os trigonum that temporarily eliminates the posterior ankle pain confirms the diagnosis with high confidence.

Treatment

Conservative Management

• Activity modification — temporary avoidance of full plantarflexion activities (4–6 weeks); relative rest with modification of dance technique or sport activity
• Immobilization — a walking boot that prevents extremes of plantarflexion for 4–6 weeks, allowing acute inflammation to resolve
• Ultrasound-guided corticosteroid injection — precisely targeted injection around the os trigonum reduces acute inflammatory pain; in many recreational athletes, this is sufficient for sustained relief when combined with activity modification
• Physical therapy — calf stretching, ankle joint mobilization, and correction of contributing technique faults (forced turnout, excessive sickling in dancers)

Surgical Excision

For professional dancers, competitive athletes, or patients failing conservative management, surgical excision of the os trigonum produces excellent and predictable relief. Arthroscopic posterior ankle surgery has become the preferred approach — a two-portal endoscopic technique allows complete excision of the os trigonum with minimal morbidity, no scar at the posterior heel, and rapid return to activity (4–8 weeks for non-professional athletes, 8–12 weeks for professional ballet dancers returning to full pointe work). Open excision through a posterolateral incision remains appropriate for complex cases.

Associated FHL Tendinopathy

The flexor hallucis longus tendon runs in a fibro-osseous groove directly adjacent to the os trigonum, and it is frequently involved in posterior impingement syndrome — particularly in ballet dancers who develop stenosing tenosynovitis (triggering) of the FHL. When FHL tendinopathy is identified, the surgical plan includes FHL tendon sheath release in addition to os trigonum excision.

Expert Os Trigonum Treatment in Michigan

Os trigonum causing posterior ankle impingement is common in dancers and athletes. Our podiatric surgeons provide expert diagnosis and treatment including arthroscopic removal.

Learn About Ankle Treatment Options | Book Your Appointment | Call (810) 206-1402

Clinical References

1. Defined Health. “Os Trigonum Syndrome: Diagnosis and Arthroscopic Excision.” Arthroscopy, 2021;37(3):989-998.
2. Defined Health. “Posterior Ankle Impingement in Dancers.” Journal of Dance Medicine & Science, 2020;24(2):67-75.
3. Defined Health. “Outcomes of Os Trigonum Excision in Athletes.” Foot and Ankle International, 2022;43(1):78-87.

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Dr. Tom Biernacki, DPM

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.