I'd go faster but my knees won't let me jog anymore.
I have knee issues as well. Imagine that. I walk between 4.2 and 4.6 mph from 30-60 mins. depending on the day. I get up at 4:30 a.m. Mon-Friday to do so. I only do an incline of 3, though.
Now when I was gone fishing, I got up at 4 a.m. and skipped the walk.