Sad truth: surgery is pretty much a toss-up when it comes to such things. Knees, hips, backs, etc. So it's possible it just got hurt in a minor way that caused pain because you're so close to having the trauma of surgery and injury there, or it could be reinjured because it didn't heal fully, or your surgeon didn't actually fix it, or so many things that any attempt to figure it out before getting it looked at will just drive you nuts. You're just going to have to have patience and optimism, as the alternative is a dark road.