He may very well have arthritis in his back legs that is radiating up thru the hips. If that is the case, try not bedding him so deep; it's a struggle for him to get thru all those shavings.
My 25 yo is like that. I have six inches of crush, with grid mats, and I only bed him in 2 - 3 inches of shavings. He does a lot better with less shavings.
If your stall mats are slick, as opposed to something textured or nobby, he doesn't have anything to grip his hooves to; they be slipping when he tries to get up and he's using his hocks in similar fashion that we use our elbows to push up --- I dunno, just theorizing on that one
Both my mid-20's Fella's hock sores disappeared when I put the grid mats down and changed shavings to the Calloway Triple Select. That was three years ago.
Anyway, Try not bedding him as deep and see what happens.
As far as duct tape on the hock sores? I've never heard of that; I'm curious if anyone has