What Causes Swollen Knee While Having Hyperthyroidism?

Hello Doctor, I m 37yr. old...i have one son of 2 yrs old.after my delivery i have got knee pain. i couldn t be able to sit down on floor then i went to my gynae and discussed about it so she prescribed me to get my calvcium serum n thyroid checked.....so i came to know that i m suffering from hyperthyroidism....it was very low...but now after one yr.it had come to the level where my physician told me to get it checked again after sometime which i have not done yet n 4 days back i had got major swelling in my rt. knee which is paining badly....so just want to know is it coz of my thyroid dose.....i m taking neo mercazole 10mg from last one yr. but is this dose gone up n i had got swelling or there might be someother reason of this swelling??