My hands have been glued to a computer keyboard of one sort or another (starting with a rubber-keyed Speccy) since 1983 (at which time I was considerably older than 3) and I've never had anything wrong with my hands or wrists that lasts more than about ten minutes (and this tends to happen when I rest them awkwardly on the desk).

I did once get tendonitis in my knees (first one, then a few months later the other one), which was odd. My doctor joked that I should stop going ski-ing until they got better.