Hi @theGuyFromGermany.
To my knowledge, Steve has had intermittent problems with his wrists for a long time. These issues seem to have become more severe with age.
If you watch this Rig Rundown from 2015, at about the 28:40 mark, an annotation indicates that Steve now wears a compression glove to help with inflammation and arthritis of his wrist. He has also switched to lighter strings and a thinner pick than he previously used.
Steve has had previous injuries due to his active lifestyle. It’s possible there is some normal degree of wear and tear to the joints from any kind of picking, he has probably picked more notes in his lifetime than any other person ever and he has always played hard, using heavy strings and heavy picks. He’s not a young man anymore. It’s hard to attribute the problems to any one cause.