Hello there,
I'm at 8 months post-op and while I'm experiencing a new problem regarding my knee, I'm pretty sure that what you are feeling is normal. At 5 months I still had pain, especially after doing specific exercises, or just being on it more than usual. If I ever was unsure about things, I contacted my PT before my OS. Usually they can clear up any questions, or just give you peace of mind knowing someone looked at it. Best of luck!