A little late for replying to this thread but it caught my eye. I used to work in restaurants before and after a while I started having the same problem with not being able to hold the knife. But being my stubborn self I still kept at it until my hands wouldn't even open up from being to tired. I look back on it now and just shake my head at what I did and how much worse it got for not resting. I was a workaholic by the way, started at 6am and finished at 12 am. One thing that I have noticed before that I never payed any attention to is the small gadgets that you can buy that will help take the load off your arms and hands for doing cutting. Now they have out pretty much what ever you need for cutting and if you want it done it doesn't take long. Just a thought there for you if you don't want to use a knife for cutting or chopping.

P.S. Always use a sharp knife though, doesn't take much to cut anything and not as dangerous as a dull knife ;-)