It's hard to tell. Stiffness is more likely fusing. If it is painful all the way around the side then is more likely Costo. I have had two pulmonary tests and my lungs are great. Dr. suggest laying on a pillow between my shoulder blades to breath better when I have a breathing spell. Now I have one of the large noodles that you get for swimming pools and lay on it and wow, it makes breathing easier and I lay on it every night just to relax me. Try to see if that helps too.
Another exercise my Dr. has me do is put my hands in the doorway and lunge so I get some good chest stretching. Hope this all helps.
