After a couple of boughts of costochondritis, which started on my left and then spread equally to both sides of my rib cage, most of my pain was on my left side. It started on the left side of my neck and then spread gradually down to encompass everything on the left. The only time it got me on both sides after that was when it spread to my feet. Now both feet hurt pretty regularly (achilles tendonitis), both wrists and both sides of the back. All of the other pains shift from side to side.
Christina
