Somehow I passed over this thread but at this late date I have to insert my 2 cents...
My wife and I are both senior citizens and we have no issue with a TC, in fact, we both like the mobility and the ease of camping just about anywhere.
Of course with a TC, you cannot take everything along, there isn't enough room so you have to pack accordingly, no issue for us.
I have the stiff joint issues too from years of manual labor and farming, so does my wife, she has bad knees.
The key is of course, getting in and getting out and of course getting into the bunk which will be above the truck cab (I'm not into sleeping on the convertible dinette either...)
My truck sits high to begin with, it's a 1 ton Ford 4x4 and it sits 4" over stock so bed height (truck bed) is 36" off the ground.
I run a set of Tirklift Revolution folding steps (4 step model with extendable and adjustable bottom pads) and they make entry and exit painless (literally). The TL Revolutions self store in their attachment bracket so you never remove them, they stay on the back of the camper all the time.
My TC has no rear bumper / landing pad, so getting in and out without steps would be impossible. The TL Revolution steps make that easy. Then we have the upper berth (bunk) issue.
If we were young'ins, getting into and out of bed would be a non-issue, just slide over the edge and place your feet on the bench below the bed (where the FW tank and batteries are). being old, that don't work well, especially at night when being old necessitates that late night potty run so, I installed a Top-Line aluminum bunk ladder with cushioned rubber treads (for bare feet use). It attaches to the bunk header with hard nylon brackets that allow the ladder to be swung up and completely removed or placed in the brackets with the rubber feet on the floor, it's very secure and don't slip because it locks in the brackets. I get into the bunk ladder style and out facing back using them stair style.
Makes getting into and out bed a snap for us.
Just some accessability suggestions from 2 old farts still truck camping...