Hi Kneeper,
Sorry to hear that the knee still gives you some problems. Its tough to say what the cause of this would be just from descriptions over the internet. Based on your previous posts, I know you are doing much better than before surgery.
Even though I can't say for sure in your case, I find that a subset of patients continue to have some aches and pains (after TKR), but still feel much better than before surgery. This is not unusual at all. My concerns would be much greater if you were having worsening pain, pain that stopped you from activities, new mechanical grinding or instability, new swelling, or pain that interfered with sleeping.
Yes, it is possible that this is just going to the new normal for you, and could be related to fibromyalgia. The most important thing is to make sure that your OS does not think that there is any specific issue with the knee prosthesis.
I hope your knee improves.
Orthodoc