I had a soft, painless, swelling on my right thumb for many years… on the outer surface and centrally located just above the joint. My Jin Shin Jyutsu practitioner thought it may have been a reaction to chronic overuse. It may also have been a reaction to habitual tension that I hold in my fingers when I’m concentrating on a project.
My family on my father’s side is also prone to developing osteoarthritic finger joints as we age. (See our article QUICK Relief for Sore, Inflamed Joints: Arthritis, Rheumatism, Injuries, etc.)