I'm a mod on two other related sites, fitness and health.
On both of those sites, questions asking for health guidance or diagnosis are closed as being off topic. Where it gets a little gray, is when they are asking about training with the injury but not about treating the injury.
If the question is something like "I have pain when I do a pushup, whats wrong?" it's closed. We can't tell what's wrong, and even if we guess, we could be in error and cause greater injury. Same with "I broke a bone, when can I train again?" - only answer is "When your doc says ok". And so on.
If the question is more along the lines of "I have a pectoral tear, what are some exercises I can do as an alternative to push ups" that would be ok. It is acknowledging the injury, but not asking for treatment/diagnosis on it. If I answer, I usually say to work with a medical professional as well.
So if it is about figuring out what causes/caused something, is my "X" healed, why does X hurt, kind of questions, off topic. The rest, case by case basis usually centered around how it is worded.