Arthritis may be to blame, however, any time you have pain from your shoulder or chest area going down your arm, it is advisable to visit you doctor immediately, so as to rule out any cardiac involvement.
tennis elbow from tennis (obviously) or pitching in baseball...and of course jerking off
bad posture, or when you are sleeping you might of slept the wrong way or side that can cause it
Dislocated Shoulder
I Originally Thought That It Was A Sign Of A Stroke Either Before Or after You've HAd One But I Can't Be Sure It Could Just Be A Pulled Muscle ??
. it was only caused of tiredness.. and stress.............. thnx... i hope .. i help you..