Hi Linh,
You mention the tibia, however I think you mean either the fibula or the talus.
Where a bony avulsion is made during an ankle ligamentous injury I don’t think I ever see perfect bony repair. The fragment never gets back perfectly placed against either the fibula or the talus to achieve a perfect union. These avulsed fragments generally end up imbedded in the granulated ATFL and if they are large they may cause some anterolateral gutter impingement like the case you also discuss in this question. We see these fragments very commonly on plain radiographs and they present as well corticated old, chronic ossicles in the area of the ATFL.
On my worksheet I just say there is an ossicle within the ATFL representing either an old avulsion fragment or dystrophic calcification from a prior injury.
As for vascularity I expect to see some increase in vascularity during the active healing phase. If it persists a month after the injury I would suggest you have some chronic post traumatic synovitis of this component of the joint capsule.
Your martial arts case sounds exactly like either anterior ankle joint impingement or anteroom-lateral gutter impingement or a combination of both.
Steve