Joints/Knees

I have never really had any major health problems associated with my weight until after my son was born.  Ever since he was born in 2008 I have been having trouble with my knees.  There are times it is painful to move and that can make Zumba difficult.  Sometimes I can actually hear them creak when I move or walk.  I know my weight puts more strain on my knees and my other joints and my heart.  I also know that I am getting stronger and my knees are getting stronger since I have been going to Curves and watching what I eat.    I am only 28 it is too soon for me to be having knee trouble and unless I want more health problems I had better get in shape now!