I have had tennis elbow--twice in my left--and it was no fun at all. The first time took a bit longer to heal but thank goodness I haven't had it since (about 10 years ago). The problem I have now is severe arthritis in my left shoulder, which has made cutting/sewing/quilting a little difficult most of the time. The doctor has recommended a shoulder replacement but I'm trying to put it off as long as possible. I'm not sure you could do this with tennis elbow, but I use one of my husband's woodworking clamps to hold the ruler and then I'm able to use my rotary cutter without having to apply much pressure.
Here's wishing you a speedy recovery.