Good job for starters & good luck - you & he will need a lot of it!!
If your friend has just rescued him, she shouldn't worry about what a vet will think of her & IME I would absolutely want X-rays, to know the extent of damage & changes. This can affect the prognosis & treatment too. Eg. Has he got enough of P3 left to make rehab to paddock soundness a possibility? Has he got loose bone chips or other stuff going on, that will need removal? Make sure 'landmarks' of hooves are marked for rads too. I'd also get rads of his knees while you're at it, as they can also be a big issue in these cases.
IMO & E it is almost always worth attempting rehab, but your friend also needs to consider his quality of life & depending on degree of damage & his level of pain it may be unfair of her not to get him on bute or such immediately & also later for when you're trimming him. Also consider what amount of continued suffering may be fair & reasonable to allow him to continue with in the process of attempted rehab.
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