Boxers also get strain injuries and overuse injuries which apparently can cause long lasting damage to legs and such. And yes you are correct. In the 1st chapter, his Hyung mentioned that "surgery and rehab" can fix his legs and that he'll shoulder the medical fees. So yeah, the hospital costs must have been too expensive for him. The fact that he also lost his job at those moments didn't help in his money problem.
Good question. Was wondering myself. From the looks of it, he came down wrong and snapped his ankle while taking a hit.. Something similar happened to me when my Gt Danes were playing and knocked me to the ground. My ankle literally went sideways. Fortunately, it didn't snap but took forever to heal. Sprains are actually worse than breaks I was told because they take longer to heal *shrugs*. But if he snapped his ankle, he would need reconstructive surgery which will require metal pins and lots of therapy which of course is expensive and he wasn't a top tier boxer. Poor guy. I'm assuming his big Mafia Daddy will eventually pay for his surgery by the end of the story.
I've been wondering this for a while, but about Sooyoung's leg injury. Is it permanent? Or will it heal? I mean, he's been having that crutch for the entire series so far. If it was gonna heal naturally it feels like it would have become better by now. But it's so sad if he'll never be able to walk again ╥﹏╥