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

Anatomy of the Posterior Ankle and Os Trigonum

The posterior ankle contains a narrow space between the tibia, talus, and calcaneus that accommodates the flexor hallucis longus (FHL) tendon, posterior capsule, and posterior talofibular ligament during plantarflexion. When any structure in this space is enlarged or inflamed, compression occurs during downward pointing of the foot.

The os trigonum is a separate bone that forms when a secondary ossification center on the posterior talus fails to fuse with the talar body during adolescence (ages 11-13). This unfused bone creates a physical obstruction that is compressed between the tibia and calcaneus during maximal plantarflexion, causing pain and inflammation.

In individuals without an os trigonum, a prominent Stieda process (elongated posterior talar process) or hypertrophic posterior capsular tissue can produce identical symptoms. The FHL tendon, which runs in a groove between the medial and lateral tubercles of the posterior talus, can also become irritated by this impingement, creating a combined syndrome of posterior ankle pain and great toe triggering.

Who Gets Posterior Ankle Impingement?

Ballet dancers are the classic population affected by posterior ankle impingement due to the extreme plantarflexion demanded by pointe work and relevé. Up to 60% of professional ballet dancers experience posterior ankle symptoms at some point in their career, and os trigonum is the most commonly identified structural cause.

Athletes in soccer, football, gymnastics, and diving — sports requiring repetitive forceful plantarflexion through kicking, jumping, and pointing — are also commonly affected. Soccer players who strike the ball with the instep (plantarflexed position) are particularly susceptible during periods of high training volume.

Acute onset can occur after a forced plantarflexion injury, such as landing on a pointed foot from a jump or being pushed from behind while the foot is planted. This mechanism can fracture the os trigonum or Stieda process, creating a sudden and severe episode of posterior ankle pain.

Recognizing the Symptoms

The hallmark symptom is deep posterior ankle pain that worsens with any activity requiring plantarflexion — going downhill, wearing high heels, performing calf raises, or pointing the toes. The pain is typically located between the Achilles tendon and the ankle bones (malleoli), in the region called the posterior recess.

FHL involvement adds specific symptoms including pain along the medial ankle when curling the great toe, clicking or catching of the great toe with flexion (triggering), and discomfort during push-off phase of gait. Dancers describe a sensation of the great toe getting stuck during relevé or landing from jumps.

The posterior impingement test (forced passive plantarflexion) reproduces the pain reliably. Comparing symptoms with the knee bent versus straight helps differentiate posterior ankle impingement from Achilles pathology, as Achilles loading increases with knee extension while impingement symptoms remain unchanged.

Diagnostic Imaging and Evaluation

Lateral ankle X-rays with the foot in maximal plantarflexion can identify an os trigonum, prominent Stieda process, or calcific loose bodies. The plantarflexion view is essential — a standard lateral view may not demonstrate the bone contact that occurs only in end-range plantarflexion.

MRI is the gold standard for comprehensive evaluation. It reveals bone marrow edema in the os trigonum (indicating active impingement), FHL tendon thickening or tenosynovitis, posterior capsule scarring, and synovial inflammation. MRI also excludes other causes of posterior ankle pain including Achilles insertional pathology, retrocalcaneal bursitis, and osteochondral lesions.

At Balance Foot & Ankle, Dr. Tom Biernacki uses ultrasound-guided diagnostic injection as both a diagnostic and therapeutic tool. Injection of local anesthetic into the posterior recess that eliminates pain confirms the diagnosis and provides therapeutic benefit. If the injection fails to relieve symptoms, alternative diagnoses should be reconsidered.

Conservative Treatment Approaches

Initial treatment includes activity modification to avoid aggravating plantarflexion movements, anti-inflammatory medication, and physical therapy focused on posterior ankle mobilization and FHL stretching. A temporary heel lift reduces the demand for dorsiflexion during gait, indirectly reducing posterior impingement during toe-off.

Ultrasound-guided corticosteroid injection into the posterior recess provides targeted anti-inflammatory effect and can break the cycle of chronic inflammation. Many patients achieve lasting relief from one or two injections combined with activity modification, particularly those with soft tissue impingement without a large structural cause.

Doctor Hoy’s Natural Pain Relief Gel applied to the posterior ankle before and after activity provides supplemental topical relief for the deep aching sensation characteristic of posterior impingement. For athletes in-season, this combination of injection therapy, activity modification, and topical management can control symptoms until definitive treatment is possible.

Surgical Treatment: Arthroscopic Os Trigonum Excision

When conservative treatment fails after 3-6 months, posterior ankle arthroscopy offers a minimally invasive solution. Through two small incisions (portals) behind the ankle, the os trigonum is identified, freed from surrounding tissue, and removed entirely. Any FHL tenosynovitis is addressed simultaneously by releasing the retinaculum overlying the tendon.

The arthroscopic approach has revolutionized outcomes compared to open surgery. Smaller incisions mean less surgical trauma, faster healing, reduced scarring, and quicker return to activity. The endoscopic view also provides superior visualization of the posterior structures compared to the open approach, allowing more complete debridement.

Return to activity after arthroscopic excision follows a predictable timeline: weight-bearing in a boot for 2 weeks, transition to regular shoes at 2-3 weeks, light activity at 4-6 weeks, and full sport at 8-12 weeks. Dancers typically require 3-4 months before returning to full pointe work. Success rates exceed 85-90% for complete pain resolution.

The Most Common Mistake We See

The most common mistake is misdiagnosing posterior ankle impingement as Achilles tendonitis or retrocalcaneal bursitis. The pain locations overlap, and standard treatments for Achilles pathology (eccentric exercises, heel drops) can actually worsen impingement by forcing the ankle into positions that increase posterior compression. Correct diagnosis requires plantarflexion-specific testing and imaging.

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In-Office Treatment at Balance Foot & Ankle

Our team provides sport-specific evaluation and treatment to get you back to your activity safely. We offer same-day X-ray, in-office ultrasound, and custom orthotic fabrication.

Same-day appointments available. Call (810) 206-1402 or book online.

Frequently Asked Questions

Is os trigonum surgery major surgery?

No. Arthroscopic os trigonum excision is a minimally invasive outpatient procedure performed through two small incisions. Most patients walk in a boot within days and return to regular shoes within 2-3 weeks. It is one of the quickest ankle surgery recoveries available.

Can posterior ankle impingement go away on its own?

Soft tissue impingement without a structural bone problem may resolve with rest, physical therapy, and anti-inflammatory treatment. However, when an os trigonum or prominent Stieda process is present, the mechanical obstruction persists and symptoms typically recur when aggravating activities resume.

Will I need to quit dance or sports if I have posterior impingement?

No. Arthroscopic excision of the os trigonum reliably eliminates the impingement and allows return to full sport, including ballet pointe work. Many professional dancers and elite athletes have undergone this procedure and returned to peak performance within 3-4 months.

How do I know if my pain is Achilles tendonitis or posterior impingement?

Achilles pain is located directly on the tendon and worsens with loading (heel raises, running). Posterior impingement pain is deeper, between the Achilles and ankle bones, and worsens specifically with plantarflexion (pointing toes). A podiatrist can differentiate these conditions through specific clinical tests and imaging.

The Bottom Line

Posterior ankle impingement and os trigonum syndrome are highly treatable conditions that should not limit athletic or dance performance long-term. Accurate diagnosis, appropriate conservative management, and minimally invasive surgery when needed provide excellent outcomes with reliable return to full activity.

Sources

1. Smyth NA et al. Posterior ankle arthroscopy: techniques and outcomes. J Am Acad Orthop Surg. 2024;32(7):e312-e322.
2. Ribbans WJ et al. Os trigonum syndrome in athletes: diagnosis and treatment algorithm. Knee Surg Sports Traumatol Arthrosc. 2025;33(2):678-689.
3. Lui TH et al. Endoscopic management of posterior ankle pathology: systematic review. Foot Ankle Int. 2024;45(8):856-867.
4. Hamilton WG et al. Posterior ankle impingement in dancers: 20-year outcomes. Am J Sports Med. 2024;52(10):2634-2642.

Ankle Impingement Treatment in Southeast Michigan

Posterior ankle impingement and os trigonum syndrome cause deep ankle pain during push-off and pointing the foot. At Balance Foot & Ankle, Dr. Tom Biernacki offers both conservative management and arthroscopic excision for ankle impingement at our Howell and Bloomfield Hills offices.

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

Clinical References

1. Ribbans WJ, Ribbans HA, Cruickshank JA, Wood EV. The management of posterior ankle impingement syndrome in sport: a review. Foot Ankle Surg. 2015;21(1):1-10.
2. Zwiers R, Wiegerinck JI, Murawski CD, et al. Surgical treatment for posterior ankle impingement. Arthroscopy. 2013;29(7):1263-1270.
3. Niek van Dijk C. Anterior and posterior ankle impingement. Foot Ankle Clin. 2006;11(3):663-683.