MRI's for knee and hip surgery

The surgeon I'm seeing has a pretty good reputation, but -- I've seen him several times to talk about hip and knee surgery. I'm very nervous about it. But I need something, since I'm in a lot of pain continually, and can't function too well. My question is this: would a surgeon usually take an MRI of knee and/or hip before surgery? He only saw an x-ray and then said, "You need a replacement on your hip and knee." Then he wanted to schedule surgery but nothing was said about an MRI. I'm seeing him again but don't really want to ask about an MRI because that might upset him. Ya think?