I have had shoulder and upper arm pain on one side since the summer and have been told it's most likely rotator cuff tendonitis, or bursitis. The pain hasn't improved with heat/cold, gentle stretching or time. It does seem to improve when I jar the shoulder; there is immediate acute pain, then I find my range of pain-free movement increases afterwards. Is this normal? I have a bit of residual pain in the back of the shoulder surrounding my armpit and am tempted to jar it to see if this will do the trick.