Hello, If you are performing repetitive activities with your arm/shoulder and you feel the pain or sensation of discomfort/swelling in the mid to upper back region where the scapula and rhomboid muscle are located then, you could have a nerve entrapment syndrome of a twig of the dorsal scapular nerve that supplies that region. I recommend seeing a neurologist and describing your symptoms. This should prompt an examination of the back and the affected area to see if you have anything that we refer to as myofascial pain. In your area of complaints, swelling, WINGING SCAPULA, or any other physical evidence of trauma or positional entrapment of even blood vessels in the area that can occur from sitting too long in one position, sleeping on the affected side without moving enough, etc. An EMG/NCV study could demonstrate abnormalities of nerves and muscles in this region as well. Also, I would recommend either a CT or PLAIN X-RAYS of the thoracic spine and right shoulder girdle in both flexion and extension positions (something not able to be done on an MR scanner) which can demonstrate other causes of this sort of pain such as arthritic degeneration, scoliosis, other skeletal abnormalities irritating structures in that region. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Dariush Saghafi, Neurologist