Os Trigonum Syndrome 2026: Posterior Ankle Pain | DPM

Quick answer: Os Trigonum Syndrome is a clinical condition that responds to evidence-based treatment when caught early. Symptoms include pain, swelling, and altered function. Diagnosis requires clinical exam, often imaging. Treatment ladder: conservative care first (4-6 weeks), then targeted interventions if needed. Call (810) 206-1402.

✅ Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatrist · Last updated April 6, 2026

Os Trigonum Syndrome: Causes, Symptoms, and Treatment

What Is Os Trigonum Syndrome?

Os trigonum syndrome is a painful condition of the back of the ankle caused by compression or irritation of the os trigonum — a small accessory bone located behind the talus (ankle bone). Approximately 7 to 14 percent of the population has an os trigonum, but most people never know it is there. Problems arise when the bone is repeatedly compressed between the talus and the heel bone during plantarflexion (pointing the foot downward), a motion common in ballet, soccer, gymnastics, and downhill running.

What Causes the Pain?

The os trigonum is either a separate bone that failed to fuse during skeletal development or a fracture of the posterior process of the talus. During extreme plantarflexion — such as a ballet dancer rising onto pointe or a soccer player kicking the ball — the os trigonum is pinched between the talus and the calcaneus. Repeated compression causes inflammation of the surrounding soft tissues, including the flexor hallucis longus tendon sheath, which runs directly adjacent to the os trigonum.

Os trigonum syndrome can also be triggered by a single traumatic event, such as a forced plantarflexion injury from missing a step or landing awkwardly from a jump.

Symptoms

The primary symptom is deep, aching pain at the back of the ankle that is worse with plantarflexion activities — pointing the toes, going up on tiptoe, or kicking. Swelling and tenderness are present directly behind and below the ankle on the outer side. The pain typically worsens with activity and improves with rest. In some cases, a clicking or catching sensation is felt at the back of the ankle.

Who Gets It?

Os trigonum syndrome is most prevalent in ballet dancers, gymnasts, soccer players, and downhill runners — athletes who repeatedly plantarflex their ankles under load. It can also affect everyday patients after a forced ankle injury or with a congenital os trigonum that becomes symptomatic with age or activity increase.

Diagnosis

Diagnosis begins with a clinical examination. A positive “nutcracker test” — pain provoked by passively plantarflexing the ankle against resistance — strongly suggests os trigonum syndrome. X-rays confirm the presence of the accessory bone. MRI is used to assess soft tissue inflammation, flexor hallucis longus tendon involvement, and bone edema.

Non-Surgical Treatment

Rest and activity modification: Avoiding the provocative plantarflexion movements for four to eight weeks. Dancers may need to take a break from pointe work.

Ice and NSAIDs: Reduce acute inflammation.

Immobilization: A walking boot may be prescribed for four to six weeks in more severe cases.

Corticosteroid injection: An ultrasound-guided injection into the os trigonum region can provide significant pain relief and allow return to activity. This is often the most effective conservative treatment.

Physical therapy: Once pain is controlled, rehabilitation focuses on restoring range of motion, strength, and activity-specific movement patterns.

Surgical Treatment

When conservative care fails after three to six months, surgical excision of the os trigonum is effective. The procedure can be performed arthroscopically through small incisions, with a relatively fast recovery of four to eight weeks for most patients. Outcomes are excellent, with most athletes returning to full sport participation.

Balance Foot & Ankle and Os Trigonum Syndrome

Our podiatrists have experience treating posterior ankle impingement conditions including os trigonum syndrome in athletes and active patients throughout Michigan. If you have persistent back-of-ankle pain with pointed-toe movements, schedule an evaluation at one of our locations.

Os Trigonum Syndrome Treatment in Michigan: Conservative Care and Surgical Excision

Michigan dancers, gymnasts, soccer players, and other athletes requiring maximal plantarflexion who develop posterior ankle pain should be evaluated for os trigonum syndrome — impingement of the accessory os trigonum bone (present in approximately 10% of the population) between the talus and calcaneus with forced plantarflexion. At Balance Foot & Ankle, os trigonum evaluation includes lateral ankle X-ray to identify the ossicle, and MRI or ultrasound when differentiation from FHL tendinopathy, posterior impingement without ossicle, or subtalar pathology is needed. Conservative treatment — activity modification, corticosteroid injection into the posterior ankle with fluoroscopic or ultrasound guidance, and physical therapy addressing posterior capsular flexibility — resolves a significant proportion of cases without surgery. For athletes who fail conservative care, arthroscopic os trigonum excision is an effective procedure with rapid return to sport in most cases. Michigan athletes with posterior ankle pain limiting their sport should call Balance Foot & Ankle at (810) 206-1402 for evaluation at our Howell or Bloomfield Township office.

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Related Treatment Guides

• Plantar Fasciitis & Heel Pain Treatment
• Stress Fracture Treatment
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Michigan patients experiencing foot or ankle problems can schedule an appointment at Balance Foot & Ankle — with locations in Howell (4330 E Grand River) and Bloomfield Township (43494 Woodward Ave #208). Book online or call (810) 206-1402.

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Related Patient Guides

• Ankle Pain: Causes by Location & Treatment
• Achilles Tendinitis: Symptoms & Treatment
• Stress Fracture in the Foot: Symptoms & Recovery

Podiatrist-Recommended Products for Os Trigonum Syndrome

Supportive footwear reduces strain on affected tendons and joints during os trigonum syndrome treatment and recovery:

See our Best Ankle Recovery Products and the full Podiatrist-Recommended Products Guide.

Visit Balance Foot & Ankle — Online Booking 24/7

Our podiatry team serves patients throughout Michigan including Howell, Brighton, and Bloomfield Township. If you’re dealing with heel pain, ingrown toenails, or a foot injury, you can book online 24/7.

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