If I haven't stated it before, I'm stating it now. In Love Knows No Bounds, Sirius escaped Azkaban in Harry's second year. He's had a trial in between the time he escaped and where the book is at now. Meaning he's also gotten medical help. He's taken nutrition potions and used medicinal balms and pastes for his injuries and scar tissue. And mental healing. Azkaban is a horrid place.
I don't understand why people write Sirius post Azkaban without him having some kind of problems, physically or mentally. It doesn't make sense. He's been imprisoned for x amount of time, he's going to have problems with certain things.