?!

... During my Physical Therapy today, I NOTICED a--NOT SEARING, but still irritating and nagging--pain in my injured, surgically-repaired LEFT shoulder.  After I "walked" across my "family room" five times, I changed my stance.  Instead of leaning so heavily on my--STRONGER--RIGHT side, I stood up straighter (... which I SHOULD'VE been doing all along).   WHAT A RELIEF!  I felt "A LOT better" (Read: "painless".) during my next/last three "walks".    "Riddle me THIS"(--'Batman Forever'): How/Why does my LEFT shoulder hurt when I lean on my RIGHT FOOT, while I WALK?!