What Causes Joint Pain?

I am a 51 yr old woman, 5 '3" about 150 pds. Pretty healthy. I had half my thyroid removed in 2008 but haven't needed any meds. For the last few years I have had very achy, sore joints. I have had my thyroid tested they say it is OK, also had the blood test for arthritis that is fine also. I am getting very frustrated as to the cause of it.