Originally Posted by Asiann
They may be better but still place a heavy load on the knees and thus tearing away at the mensicus which is the bodies version of the shock absorber. He needs to stay clear of treadmills anyway because of his back pain. Elliptical trainer, deep water running and cycling are the best choice for exercises. Rubber tracks also work well to provide better cushioning than the road.
I believe he's trying to get in shape for the Rock n' Roll Half marathon in Virginia Beach Labor Day weekend. A low impact cushioned treadmill can't hurt when he's not able to jog outside.