My wife has a bad left knee and cannot twist it, or risk twisting it, so when she gets on the bike she puts her left foot onto the rear peg facing forwards as much as possible, then, with her left hand on my left shoulder and gripping the rack (fitted for the purpose) on the back box with her right hand she can pull herself up, she then does the smallest of hops, taking some of her weight via me and the back box to completely straighten the left foot, then puts the right leg over the seat and onto the right peg. She does the same if the panniers are fitted.
She's been doing this now for seven years, on this bike, and has been on the back for the majority of the 40k the bike has done and there is no serious damage to the rubber, a bit of wear yes, but not bad.