So far, as I know, there is no convincing conclusion on this phenomenon. Many debates on whether it is really correlated and there are studies with dividing data and opinion. However,several hypothesis suggest barometric changes may affect the pressure within the joint and thus altering its anatomical structure. Some hypothesize the homeostasis of internal environment could have been changed under humidity and pressure change. Inflammatory chemical mediators may change to the "weather sensitive" patients.Cold weather causes contracture of the muscle fibers. However, none of the theories are commonly accepted. The question is large sample study of this is not considered as clinically worthwhile and cost effective yet. That is so far as I know of about this question.