I have an adventurous Lab who has some knee issues, including lots of arthritis. She's sound to run and climb, and more than game, but she wears out faster than she used to. Is this pack something we can use to give her a boost when needed and help her up the stairs, like the web harness is supposed to be?

In that case this should be fine, the harness on the pack is exactly like the web harness. btw, I was in no way questioning your intentions, just throwing the thought out there in case it hadn't crossed your mind.

I want a harness to help move her. Her knees are arthritic, not weak. She is cleared for all activities by two veterinary surgeons. This pack would be purchased on their recommendations, as they suggested a sound body harness for assists, rather than the standard hospital practise of looping a leash under the dog's tummy. She's only ever carried her empty plastic poop bags and occasionally a water bowl. The stores near me only have this pack in her size, not the web harness. It was merely an inquiry as to the quality of support provided, and certainly no indication that I would intentionally hurt my dog or ask her to carry any undue burden for goodness sake!

It will provide some support for lifting her over small obstacles. Don't know if I would use it to lift her entirely off the ground though. But why would you want to put a pack on her that would only add more weight and stress to her already weak joints?