How long does pain last after arthroscopic knee surgery?

I had knee surgery 6 months ago and although my initial pain is better I have stiffness pain that is unbearable after sitting for too long. I asked my doctor how long do I have to suffer everytime I stand up and he said everyone is different and had no idea but to give it about a year... I take ibruprofen everyday and it seems to take the edge off but i still use percocet when I am in real pain.