SOUNDS LIKE BRSITIS TO ME ALSO IN THE SHOULDER AREA ON DOWN. VERY PAINFUL AT TIMES. I HAVE IT AND IT MAKES IT HARD TO SLEEP. SEE A DOCTOR TO BE SURE AND GET HELP.
It could be tendonitis, carpal tunnel, bursitis. Also, possible rotator cuff injury (which I just had) refers pain and it shows up in the deltoid area as sharp pain there. Have you been doing repetitive work or sports? Arthritis is usually not sharp it is more of an aching pain. So, there seems to me to be an injury. If your family practice doctors ignore it you may want to see a orthopedic specialist.