Couple of things.
I have a friend with a replaced right knee and no other joint problems. He stands on the left foot rest with his left foot while straddling the bike. Then he basically climbs up on the kickstarter with his right leg and with a straight leg rides it down. Seems to work fine - just worries me what would happen in a kickback. He's about 5'10" and maybe 160 pounds.
My left side joints (shoulder, hip, knee, ankle, foot) have been replaced/repaired. My right hip and knee are not good, but no surgery. It's comical watching me climb on a bike and I cannot start a Norton while straddling the bike. I put it on the center stand, stand on the right side, and kick with my right leg. That seems easier than I remember while straddling the bike. I'm 6'1" so that could have something to do with it - my knee is not very bent when I'm applying force. I haven't tried my left leg on the right side of the bike, but I suspect that I could do it even with all the bad joints.