What Causes Pain And Stiffness In Legs, Thighs And Buttocks?

Hi Doctor.My name is Allen...For the last year I have had stiffness in my legs,thighs,and buttocks.pain & stiffness mostly on the right side.I did walk a lot until about a year ago,now when I walk I have a shortness of breath.perhaps you can give me some answers.Thanks doctor..Allen