| Condition | Location | Pain Pattern | Provocative Test | Imaging | Treatment |
|---|---|---|---|---|---|
| Os Trigonum Syndrome | Posterior ankle (posterior to talus) | Deep posterior pain with plantarflexion (pointing foot); worse in dancers, kickers | Forced plantarflexion compression test (Nutcracker test) | Lateral X-ray: separate ossicle posterior talus; MRI: bone marrow edema | Boot immobilization; corticosteroid injection; endoscopic excision |
| FHL Tenosynovitis | Posterior-medial ankle (flexor hallucis longus tunnel) | Posteromedial pain; hallux triggering (catching, locking); pain resisted toe flexion | FHL resistance test; hallux triggering reproducible | MRI: FHL tendon sheath fluid, tear, or stenosis | PT + NSAIDs; corticosteroid injection; endoscopic FHL release |
| Posterior Tibiotalar Impingement | Posterior joint capsule (Stieda process variant) | Pain similar to os trigonum; prominent posterior talar process on imaging | Forced plantarflexion test positive | CT: large Stieda/Cedell process; MRI: edema | Endoscopic spur resection |
| Peroneal Tendon Pathology | Lateral posterior ankle (fibular groove) | Lateral pain with inversion/eversion; instability; snapping | Peroneal subluxation test; resisted eversion pain | MRI: peroneal split tear, retinaculum tear, subluxation | Repair retinaculum; groove deepening; tendon debridement |
| Achilles Insertional Tendinopathy | Achilles insertion at posterior calcaneus | Pain at very back of heel (not deep ankle); worse with shoe counter pressure | Palpation of Achilles insertion; Haglund sign | X-ray: Haglund deformity; MRI: tendon changes at insertion | Heel lifts; ESWT; calcaneoplasty + detachment repair if severe |
| Treatment | Indication | Technique | Success Rate | Recovery |
|---|---|---|---|---|
| Activity Modification + NSAIDs | All patients first-line; acute flare | Avoid forced plantarflexion; 2–4 weeks | Temporary relief; not curative | 2–4 weeks |
| CAM Walker Boot | Moderate symptoms; dancer pre-season preservation | 4–6 weeks boot immobilization; limits plantarflexion stress | 50–65% temporary relief; high recurrence off boot | 4–6 weeks; return to sport 2–4 weeks post-boot |
| Ultrasound-Guided Corticosteroid Injection | Persistent pain after conservative care; pre-surgical diagnostic | US-guided into posterior ankle recess near os trigonum | 60–70% short-term; 30–40% durable relief at 1 year | Days to 2 weeks for effect |
| Endoscopic Os Trigonum Excision | Failed 3–6 months conservative care; symptomatic os trigonum confirmed | Posterior 2-portal endoscopy; os trigonum resection; FHL inspection | 85–95% excellent outcomes; low recurrence | 2–3 weeks non-weight-bearing; 6–8 weeks return to dance/sport |
| Open Posterior Excision | Large os trigonum; complex posterior pathology; failed endoscopy | Posteromedial or posterolateral open approach; bone excision | 80–90% | 6–8 weeks; longer than endoscopic approach |
Watch: Inside of the Ankle Pain [Posterior Tibial Tendonitis Treatment] — MichiganFootDoctors YouTube
Foot pain isn't resolving?
Same-week appointments at Howell & Bloomfield Hills
Medically Reviewed | Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle, Michigan
Quick Answer:
Quick Answer: Os trigonum syndrome is posterior ankle impingement caused by compression of an accessory bone (the os trigonum) between the heel bone and the shinbone when the foot is pointed downward (plantarflexion). It is most common in ballet dancers, soccer players, and downhill runners. Dr. Biernacki treats os trigonum syndrome with cortisone injection, rest, and physical therapy initially—and arthroscopic or open excision of the bone when conservative measures fail.
Os trigonum syndrome is a specific type of posterior ankle impingement caused by a small accessory bone—the os trigonum—located just behind the ankle joint at the back of the talus (ankle bone). When present (in approximately 7–14% of the population), the os trigonum can become painful when the foot is forcibly pointed downward (plantarflexion). This is exactly the movement required in ballet’s en pointe position, soccer goal kicks, and downhill sprinting—explaining why this condition disproportionately affects certain athletic populations.
What Is the Os Trigonum?
The os trigonum is a secondary ossification center—a small bone that forms separately from the posterior process of the talus during skeletal development and, in most people, fuses into the main talus bone during adolescence. In roughly 7–14% of adults, this secondary center fails to fuse, persisting as a separate bone connected to the talus by fibrous or fibrocartilaginous tissue. The bone itself is not the problem—it only becomes symptomatic when it gets mechanically compressed (impinged) between the back of the tibia and the calcaneus (heel bone) during maximum plantarflexion.
Acute injury—a forced plantarflexion stress such as landing hard on a pointed foot—can cause a symptomatic fracture through the synchondrosis (the junction between os trigonum and talus), mimicking os trigonum syndrome. This is called a “Stieda process fracture” and presents identically to classical os trigonum impingement, though the acute onset and often more severe pain help distinguish it clinically.
Symptoms of Os Trigonum Syndrome
The hallmark symptom is deep pain at the back of the ankle—posterior to the Achilles tendon and the ankle joint itself—that worsens with maximal plantarflexion. Dancers describe increased pain when rising on pointe or demi-pointe. Soccer players note pain when kicking with a fully extended foot. Stair descenders and downhill runners experience it with each step as the foot extends at push-off.
Associated findings include posterior ankle swelling, tenderness directly over the back of the talus on palpation, and pain with passive plantarflexion applied by the examiner. The posterior impingement test—rapid passive plantarflexion of the ankle—is positive when it reproduces the patient’s characteristic pain. Weakness in ankle plantarflexion can occur if the adjacent flexor hallucis longus (FHL) tendon is irritated by the impinging bone—a common concurrent finding called FHL tenosynovitis that adds big toe stiffness to the clinical picture.
Diagnosis: Imaging for Os Trigonum
Lateral weight-bearing ankle X-rays are the first step. The os trigonum appears as a smooth, rounded ossicle behind the posterior process of the talus on lateral view—distinguishing it from a fracture of the posterior talar process (Shepherd’s fracture), which shows irregular edges. The size of the os trigonum varies from a small corticated fragment to a large rounded bone that significantly occupies the posterior ankle space.
MRI is invaluable for confirming active impingement and ruling out concurrent pathology. Bone marrow edema (bright signal on STIR sequences) within the os trigonum and adjacent posterior talus confirms mechanical stress and inflammation. MRI also evaluates the FHL tendon for tenosynovitis—critical because FHL involvement changes both conservative and surgical treatment planning. CT scan is occasionally used to precisely characterize bony anatomy before surgery.
Conservative Treatment of Os Trigonum Syndrome
Conservative management is the appropriate starting point for most patients. Activity modification—avoiding or reducing plantarflexion-demanding activities—combined with relative rest allows acute inflammation to settle. Anti-inflammatory medications (oral NSAIDs or topical diclofenac) reduce synovial irritation around the impinging bone.
Ultrasound-guided cortisone injection into the posterior ankle joint or around the os trigonum is both diagnostic and therapeutic. Significant pain relief following injection confirms os trigonum as the pain generator—differentiating it from other posterior ankle pain sources like Achilles tendinopathy, retrocalcaneal bursitis, or FHL tendinopathy. Studies report 50–70% short-term improvement with injection, with some patients maintaining relief for months to over a year, particularly those with mild chronic impingement rather than acute symptomatic episodes.
Physical therapy focuses on posterior ankle flexibility, proprioception, and strengthening of the intrinsic foot muscles and calf complex. Dance-specific rehabilitation programs work with technique modification—adjusting turnout mechanics and pointe training volume—to minimize impingement forces at the posterior ankle while maintaining performance capabilities.
Surgical Excision of the Os Trigonum
When 3–6 months of conservative treatment fails to provide lasting relief, surgical excision is highly effective. Two approaches exist:
Arthroscopic excision uses posterior ankle portals—small incisions on either side of the Achilles tendon—to introduce the camera and instruments into the posterior ankle compartment. The os trigonum is identified, separated from its fibrous attachment to the talus, and removed. Any concurrent FHL tenosynovitis is addressed in the same procedure. Arthroscopic excision has become the preferred approach at high-volume centers: it offers faster recovery (typically 6–8 weeks to return to dance/sport vs. 8–12 weeks open), reduced scar tissue, and equally good outcomes compared to open surgery.
Open excision via a medial or posterolateral approach is appropriate when the os trigonum is very large, when concurrent pathology requires open repair, or when posterior anatomy makes arthroscopic access technically challenging. Outcomes are equivalent but rehabilitation is typically longer.
Published outcomes for os trigonum excision are excellent: studies of professional and pre-professional dancers show 85–95% return to full dance activity following surgical excision, often within 3–4 months of the procedure.
Dr. Tom's Product Recommendations
Vive Ankle Brace with Stabilizer
⭐ Highly Rated | Foundation Wellness Partner | 30% Commission
Adjustable ankle support that restricts extreme plantarflexion, protecting the posterior ankle during activity.
Dr. Tom says: “Wore this through the rest of my season after diagnosis—helped me manage until I could get treatment.”
Athletes needing to continue activity during conservative management
Post-surgical patients without specific surgeon clearance
Disclosure: We earn a commission at no extra cost to you.
Hyperice Venom 2 Ankle Heat & Vibration
⭐ Highly Rated | Foundation Wellness Partner | 30% Commission
Heated vibration therapy wrap for posterior ankle pain management and pre-activity warm-up.
Dr. Tom says: “Game-changer for loosening up the back of my ankle before practice.”
Dancers and athletes using heat/vibration for pre-activity preparation
Patients with open wounds or acute inflammatory flares
Disclosure: We earn a commission at no extra cost to you.
PowerStep Pinnacle Insoles
⭐ Highly Rated | Foundation Wellness Partner | 30% Commission
Supportive insoles that improve overall foot and ankle biomechanics, reducing abnormal stress at the posterior ankle.
Dr. Tom says: “My podiatrist recommended these alongside physical therapy—helped keep me active.”
Athletes managing os trigonum pain in everyday and training footwear
Ballet-specific footwear (requires dance-specific inserts)
Disclosure: We earn a commission at no extra cost to you.
✅ Pros / Benefits
- Arthroscopic os trigonum excision has 85–95% return-to-sport rates in athletes and dancers
- Minimally invasive surgery means small incisions, fast recovery, and minimal scarring
- Ultrasound-guided injection is both diagnostic and therapeutic—confirming the diagnosis while providing relief
❌ Cons / Risks
- Conservative measures only delay surgery in patients with large symptomatic os trigona
- FHL tendon involvement (concurrent tenosynovitis) lengthens recovery and must be addressed
- Not everyone with an os trigonum on X-ray has symptoms—incidental findings are common
Dr. Tom Biernacki’s Recommendation
Os trigonum syndrome is one of my favorite diagnoses to make because it’s so satisfying to help patients who’ve had undiagnosed posterior ankle pain for months or even years. Once we identify it on imaging and confirm it with a diagnostic injection, the treatment path is clear. For most active patients—especially dancers and soccer players—who’ve tried conservative care without lasting results, I recommend arthroscopic excision. The procedure takes about 45 minutes, recovery is measured in weeks rather than months, and the vast majority of my patients return to full activity with a posterior ankle that finally feels normal. If you have nagging pain in the back of your ankle when you point your foot, come see us—don’t assume it’s just a sprain that needs to be toughed out.
— Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle
Frequently Asked Questions
Is os trigonum syndrome the same as a posterior ankle sprain?
No—though they can be confused. Os trigonum syndrome causes deep posterior ankle pain specifically with plantarflexion (pointing the foot), while posterior ankle sprains typically involve the posterior talofibular ligament and cause pain with inversion and dorsiflexion. A lateral ankle X-ray showing the accessory bone, combined with a positive posterior impingement test, distinguishes os trigonum syndrome from ligamentous injury.
Can os trigonum syndrome go away without surgery?
Some patients achieve long-term relief with conservative management—particularly injection combined with activity modification and physical therapy. However, for high-level athletes and dancers whose sport requires repeated plantarflexion, definitive surgical excision is often necessary for sustained return to performance. Dr. Biernacki takes a thorough conservative approach first, with surgical excision reserved for refractory cases.
How long after os trigonum surgery can I dance or play sports?
Arthroscopic excision patients typically return to light training at 4–6 weeks and full sport/dance at 8–12 weeks. Professional dancers at ballet companies often return to stage performance within 3–4 months following surgical excision, based on published case series from major dance medicine centers.
Does everyone with an os trigonum need surgery?
Absolutely not. An os trigonum is present in 7–14% of the population and most people with one never develop symptoms. Only symptomatic os trigonum syndrome—confirmed by clinical exam, imaging, and often diagnostic injection—is treated. Many symptomatic cases resolve with conservative management. Surgery is reserved for refractory cases.
Where is Balance Foot & Ankle located and how do I schedule?
Balance Foot & Ankle is located in Howell, Michigan, serving patients from across Southeast and Central Michigan. Schedule online 24/7 at MichiganFootDoctors.com or call (517) 579-1881 for same-day or urgent appointments. Dr. Biernacki offers telehealth consultations for patients from more distant areas of Michigan.
Michigan Foot Pain? See Dr. Biernacki In Person
4.9★ rated | 1,123 Reviews | 3,000+ Surgeries
Same-week appointments · Howell & Bloomfield Hills
📞 (810) 206-1402 Book Online →Frequently Asked Questions
When should I see a doctor?
See a podiatrist if pain persists past 2 weeks, prevents normal activity, or is accompanied by red-flag symptoms (warmth, swelling, numbness, inability to bear weight).
Can I treat this at home?
Mild cases respond to RICE protocol (rest, ice, compression, elevation), supportive shoes, and OTC anti-inflammatories. Persistent symptoms need professional evaluation.
How long does it take to heal?
Most soft tissue injuries resolve in 2-6 weeks with appropriate care. Bone injuries take 6-12 weeks. Chronic conditions need longer-term management.
Visit Balance Foot & Ankle — Same-Day Appointments Available
Our podiatry team serves patients throughout Michigan including Howell, Brighton, and Bloomfield Hills. Whether you’re dealing with heel pain, ingrown toenails, or a foot injury, we have same-day appointment availability.
Same-day appointments available. (810) 206-1402
Doctor Hoy’s Natural Pain Relief Gel
Natural topical pain relief I use in our clinic. Arnica + camphor formula — apply directly to the area 3–4x daily. ($20–25)
Shop Doctor Hoy’s →Our podiatrists treat the underlying cause, not just the symptom. Same-week appointments at our Howell and Bloomfield Hills, Michigan offices.
Same-Week Appointments in Howell & Bloomfield Hills
Three board-certified podiatric surgeons. 1,123+ five-star reviews. Most insurance accepted.
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.
- Plantar Fasciitis: Diagnosis and Conservative Management (PubMed)
- Plantar Fasciitis (APMA)
- Diagnosis and Treatment of Plantar Fasciitis (PubMed / AAFP)
- Heel Pain (APMA)
Recommended Products from Dr. Tom