Maybe you TSH is still a little high.
Here is a link explaining hypothyroidism and the link to arthritis, among other things.
http://www.clevelandclinic.org/arthritis/treat/facts/Endocrine%20Disorders.htm
Just had a total hyroidectomy 3 days ago. Dr. has me on 50 mg Synthroid and I'm jumping out of my skin here. Can't sleep, heat intolerance, looking for things to do at 2:30 in the morning. Just made a big pot of soup and about to get the sewing machine out and start mending stuff. Feels like I'm hyper still!!! Any suggestions till I can call him in the morning? Diane