The latest knee MRI I had was in February 2003 (I had a total of 5 knee MRIs). It was an open MRI scanner which covered my body from the waist down. I was given headphones to block out the noise and listen to some music. The MRI took about 40 minutes. If you feel apprehensive or anxious, you might want to ask your doctor to prescribe a sedative for you.
I hope this helps.