injury due to injury Missouri

[slippingirl]

I'm an employer in Missouri. One of my employees had wrist surgury for a non work related injury and was off work for a few weeks. When her doctor cleared her for light duty, she was assigned to the cash register, where she wouldn't have to do any lifting and someone was always close to help her with things she felt she needed help with. She is now complaining, not to me, to other employees that her other wrist is bothering her. She has said nothing to me.

I do not want her other wrist injured in part due to her work, she had trouble with it before coming into my employment, but what am I to do?

When I ask her how she is doing she says everything is fine. She needs the money and wants to keep working, but I don't want a workman's comp claim, what should I do?