Muscle and joint pain or stiffness are definitely things I regularly experience as a result of Letrozole. I find ensuring hydration is a must as well as trying not to over exercise or rush movement especially first thing in the morning. Sometimes there's just an 'ache-y' feeling either throughout my body or in specific areas. A friend gave me a wonderful cushion from 'Comfort Station' and I use this often to relieve a sense of weightiness in my legs & arms. Overall though increasing my hydration has really helped.