The Heininger TruckStep provides so much relief for your knees and related cartilage that is should be covered under your medical insurance.
Install the TruckStep in your receiver hitch in only a few minutes. Then either push it back into the receiver and fold it up when not in use or extend it out to provide an easy step into and out of your truck with the tail gate up or down.
HitchMate TruckStep extends anywhere between 5" to 23" from the receiver and can handle up to 500 pounds. Accepts a hitch lock to prevent theft (not included).