Evidentially, tenosynovitis is common here in Japan. It occurs from repeated misuse of your wrist in everyday activities. In my case, I had a painfully swollen hand, where I couldn’t grip or use my fingers for several days.
With a hand brace, resting my arm and antibiotics for the swelling, it eventually healed. I think my case occurred from using a computer mouse, and bad hand positioning (ergonomics are VERY IMPORTANT). When I use a computer mouse now, I put some padding under my wrist, but I do experience some fatigue in my hand, more than before. When that happens, I give my hand/wrist a break.
Below is a link to an article describing tenosynovitis in more detail:
Please take care!!