Unless one is confined to a bed, I think MA can still be practiced in some form in most cases (maybe less so for grappling arts). Bad leg? Practice hands. Bad arm? Practice footwork. Other problems? Slow and easy kata. Where there's a will, there's a way. As Bill and Gyakuto noted, teaching, analyzing others and visualization can be most helpful and give further insights. Reading MA subjects, comparing on-line videos and other mental exercises can be done, even if bedridden.
But taking a few weeks off won't hurt any serious practitioner. Getting back into the groove won't take any longer. In the meantime, having your significant other waiting hand on foot on you and baking cookies should be milked for as long as possible. (I think this last one was mentioned somewhere in The Bubishi.)