Dear Dr. I Am Goitom From Ethiopia. My Mum Have

Dear Dr. I am Goitom from Ethiopia. My mum have been in a chronic pain around her knee since 8 years now. she went to see a doctor but no change at all. Before it was only one of her legs and and now it is even both.it gets more pain when the weather is more cold, in the nights for example? what kind of disease can this be?