Q: I recently went to a sports medicine specialist who told me I have "os trigonum syndrome". Could you tell more about this?
A: Runners who have pain in the back of their heel with stiffness and swelling must be checked for this condition. Os trigonum syndrome is caused by an 'extra' bone in the back of the heel bone. A lateral X-ray of the ankle is needed when this diagnosis is suspected and at times a bone scan or MRI is ordered to confirm the anatomic detail of the area. During the foot's skeletal development sometimes a separate area of bone develops in children usually between the ages of 8-13. This separate area normally fuses with the remainder of the heel bone within 1 year of its appearance. However, an os trigonum, an accessory bone, forms if this secondary bone center fails to fuse after skeletal maturation.
The foot may have up to 21 accessory bones. The prevalence of the os trigonum has been reported from 2-20% (of the known accessory bones). The bone is usually triangular in shape and about 1 cm in diameter. Many runners who run downhill often and have this extra bone may become symptomatic from this.
The initial treatment of the os trigonum syndrome is conservative and includes anti-inflammatory agents, a relative rest period, weight bearing modification, and formal physical therapy. If conservative measures fail we recommend arthroscopic removal of the os trigonum which results in good outcomes most of the time.
