A vet may be able to solve the problem. Or a good equine chiro. I consider it irresponsible for a horse not to get help when it's so clearly in pain. Even if it's just to find out that there's nothing that can be done, because sometimes knowing that is the most powerful thing of all. It allows us to decide whether to retire the horse, or to dose it up on painkillers so that it can continue living a productive life.
My mother, after owning her horse for a year, finally got a lameness exam done on him because he'd been sore on and off for a long time even before she took him on. Vet doesn't think anything can be done. But sometimes, things CAN be done. Sore muscles can be released and made comfortable, or arthritic joints can be injected. Hooves can be shod or improved.
I must ask you - IS he uncomfortable in the pasture or just under saddle? Because if he's unhappy even in the pasture, there's quality of life to consider. It's a bit selfish of your friend to not see a vet because "oh a few people have said that now". In fact I would be inclined to go the opposite, get a vet BECAUSE a few people said he looked off. That might be just me though?
A CLEAN SLATE FOR THE FUTURE