I am SO sorry she is going through this. I do not know of anything to help as immobilization is one of the worst things for CRPS. Sometimes it is unavoidable though. Did they give a timeline on how long she needs to have this on? Do they think the dislocating problem will be FIXED by the cast or is it just intended to be a bandaid for the problem until some other treatment is offered?

I would definitely see the doctor who treats her for the CRPS and make sure they are kept in the loop on anything that is being done for her knee. The doctors will need to work together to make sure they are giving your wife the care and support she needs through this.