If you want details I can go into it! To keep it reasonably simple though; usually with a patellar dislocation you'd just treat with physio, strengthening the muscles surrounding the knee to prevent re-occurrence, this gives a shorter period of recovery however leaves you with a decent chance of re-occurrence happening, especially in people undertaking sports such as football. Or, as in Gundogan's case, if you suspect a reason for the dislocation or want to stabilise the patellar further you can have surgery, this will get you back down to essentially standard levels of risk for dislocation happening in the future (
i.e. he'll have the same risk as any United player has of dislocating theirs) - with surgery though the recovery time will be increased, hence why he's now out for longer than it would usually take to recover from this injury.
So yes, in terms of his knee it's now fixed, not sure when he had the op but from what I've read in recent interviews he's expected back around the time of the first international break (just before the derby).
Not sure what your posts point was exactly, but hope that helped