Aches and pains including joint pains are quite common during a fast, so nothing to be overly concerned about. They come and go as they please as symptoms of detox.
Shelton has this to say concerning this problem........
"Besides pains in the back, usually in the lower spine, there frequently develop in the early days of the fast, pains in the hips, pains at the base of the skull and aching in the limbs, particularly in the joints. These pains and aches are often very annoying, but seldom last more than one or two days. They develop chiefly at night and cease during the day". http://www.soilandhealth.org/02/0201hyglibcat/020127shelton.III/020127.ch28.htm
In my experience, and although Shelton has said they only last a day or two, they can last much longer these days as we are more toxemic now than they were in his day.