There are sever causes of pain in the thumb. The particular pain in this video is caused by repetitive bending of the elbow.
Some activities that create the problem are window washing, house painting, drumming, violin playing, hammering, some cleaning activities, some assembly line work.
This is referred pain. If you have pain when you push on the thumb, particularly the thick muscle at the base of the thumb, that is a different kind of problem and is caused by gripping.
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