"Restrictions will apply to standard hip and knee replacements".
If there isn't much point, medically, in replacing a knee or hip joint because the patient is enough overweight to defeat the purpose of the operation by continuing to put excess pressure (weight) on the joint thus preventing a new joint from being of much benefit to them, then such a restriction doesn't seem draconian to me.
If there is a shortage funds (I'm talking about fact here, not political reasons for shortage of funds; that's a separate issue), then it would be stupid of health trusts to waste money on pointless treatments, treatments that won't do any good. Or so it seems to me, logically.
I imagine health trusts have to make choices like this all the time about whether a treatment will be of benefit to a patient or whether it would just be a waste of money, time, and professional skill. I don't have a moral objection to that; I reckon it's inevitable in any human situations.
Nor do I have a problem with the idea that, at least to some extent (repeat: some extent ) people are and should be held responsible for their own health. If their behaviour shows that they are not helping themselves in a situation where it's very difficult for anyone else to help them (e.g. eating less), then... shrug.
"Do no harm". It's not the health trusts that will be doing the harm here. If it happens.