I've always wondered if John Ritter (as Jack Tripper) had ever hurt himself during filming of Three's Company. There's alot of physical comedy, and I wonder if he ever received an injury from it. There is nothing online about it.
While there's no concrete evidence to confirm or debunk this question, it's probable he never sustained any serious injury based on some information obtained online.
According to this list of on-set injuries, there is no entry for John Ritter prior to his death while filming an episode of "8 Simple Rules".
According to the Three's Company episode guide, there was never any extreme gap in air dates that would indicate a lengthy hospital stay or recovery from broken bones.
So, while it's probable he sustained bumps and/or bruises doing some of his comedy scenes, it doesn't appear that it was anything more than that.