Management of 12-mm Os Trigonum in a Runner
Refer this runner to a foot-ankle orthopaedic surgeon or sports medicine specialist for evaluation of surgical excision, especially if conservative treatment has failed or symptoms persist beyond 3 months. 1, 2
Initial Conservative Management (If Not Already Attempted)
Before referral, ensure the patient has undergone appropriate conservative treatment:
- Activity modification: Reduce or temporarily cease running and activities requiring repetitive plantarflexion 1, 3
- Physical therapy: Focus on ankle range of motion and strengthening exercises
- Orthoses: Consider heel lifts to limit plantarflexion 1
- NSAIDs: May be used cautiously for pain and inflammation, though they may suppress natural healing 4
Duration: Conservative treatment should typically be attempted for 3 months before considering surgical referral 5, 6
When to Refer (Surgical Indications)
Refer immediately if:
- Persistent pain or functional limitations despite 3 months of conservative treatment 5, 6
- Significant impact on athletic performance and quality of life
- Patient desires prompt return to competitive running 5
The 12-mm size is clinically significant and commonly symptomatic in athletes performing repetitive plantarflexion activities like running 1, 2.
What to Tell the Patient
Explain the condition:
- "You have an extra bone fragment behind your ankle called an os trigonum—it's present in about 10-15% of people but usually doesn't cause problems"
- "In runners, repetitive push-off motion causes this bone to get pinched, creating posterior ankle impingement"
- "Your 12-mm os trigonum is large enough to be causing your symptoms" 1
Discuss prognosis with surgery:
- Excellent outcomes: Studies show VAS pain scores improve from 7.5 to 0.3-0.6 within 2 years 2
- Return to sport: Most athletes return to training at 8 weeks and full competition at 3 months 2, 7
- Success rate: 95% of recreational athletes return to previous sport level 2
- Functional improvement: AOFAS scores improve from 39 to 98 postoperatively 2
Surgical approach:
- Posterior ankle endoscopy is preferred over open surgery 5, 2, 6, 3
- Benefits: Less scarring, less postoperative pain, faster return to activity 3
- Complication rate: Only 6%, mostly transient nerve symptoms 5
- Only 5 complications in 81 patients, with 4 being transient 2
Common Pitfalls to Avoid
Don't delay referral excessively: Longer preoperative pain duration correlates with delayed return to training and return to sport 8. If conservative treatment fails at 3 months, refer promptly.
Screen for concomitant pathology: Flexor hallucis longus (FHL) tenosynovitis is the most common associated condition 3, 8. Ask about:
- Pain with great toe flexion
- Clicking or catching sensation
- Tenderness along the posteromedial ankle
Assess FHL involvement: Recent evidence suggests FHL muscle morphology (specifically a lower musculotendinous junction) may contribute to os trigonum syndrome 9. The surgeon will evaluate this during endoscopy.
Contraindications to Surgery
Do not refer if patient has:
- Severe ankle arthritis
- Poor vascular status
- Compromised soft tissue envelope 5
Bottom Line
For a runner with symptomatic 12-mm os trigonum causing posterior ankle impingement, surgical excision via posterior ankle endoscopy offers excellent outcomes with minimal complications and rapid return to sport—but only after conservative treatment has been appropriately attempted for 3 months. 2, 6, 8