Brief Answer:
Tricky.

Detailed Answer:
Anywhere in the area can be the cause. Most common is an irritation of the elbow joint due to overuse. Rest, a sling, anti-inflammatories, perhaps heating pad, and it gets better in most people fairly quickly (a week). There is one nerve that runs over the elbow. Most people know it's a nerve because electrical or tingling occurs when it is sharply/acutely injured (funny bone). BUT it can also become chronically irritated. The pain goes over a wider area than the pain from just an arthritis, but responds to the same Rest, a sling, anti-inflammatories, perhaps heating pad, and with about the same time to recover. Both of these recur. Can be a sore muscle. Mostly that is pretty obvious because it is sore to the touch and moving the muscle hurts... again Rest, a sling, anti-inflammatories, perhaps heating pad. AND... can be a problem in the neck. A pinched nerve in the neck can cause (generally SHOOTING, electrical, sometimes BURNING) pain in a line out from the neck, out the shoulder, down the arm and out to the hand. Often moving the neck triggers the pain. Rest would involve a cervical collar, but its response to rest, etc is nowhere near as good as the other conditions because there is something actually permanently damaged in the neck source of pain and not so in the others.

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Brief Answer:
well.... mostly....yes....

Detailed Answer:
depends a lot on the complexion of the person and how muuch fat they have under the skin. This isn't that abnormal. If the web look goes away with not having the heat on it, then seems even less of an issue... several other points... could see how the OTHER arm reacts to heat. Also, this isn't all that bad, but... some people with pinched nerves have somewhat reactie vessels and the circulation changes with changes in temperatture. Mostly, though, relief with local treatment stongly implies that a local minor problem is underlying it.

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