Anyone can RICE their joints. It's foolproof, more or less objective and requires no monitoring from a professional.
What defines optimal load? It sounds impossible to gauge, unless maybe if you're working with a physical therapist. Then, what happens if load more than the optimal level? Is the outcome worse than if you just stuck to RICE? I think these are things that have to be considered for medical protocols.
RICE, as a protocol, isn't all that effective. The doctor who invented it recanted support after new evidence showed the importance of inflammation for the healing process. And, it turns out, he just kind of made it up to fit a handy pneumonic. POLICE is similarly invented and hard to recommend, but modern practices do recommend bearing load sooner rather than later. Can determining optimal load be done without a doctor? It probably depends on the severity and type of injury. But that's not really the point of a medical protocol, the point is to define best practices that help achieve the best outcomes.
When I broke a joint in my pinky a few years ago it was pretty easy to tell. Early on the range of motion was the limiting factor, and I'd move it back and forth as much as I could without any pain. After that I worked on strength in a similar way, do as much as I can with no pain. I went from "you'll never play an instrument again" to rock climbing and Viola practice.
Overall, seeing my strength and range of motion slowly get better was immensely satisfying and your body is pretty good at letting you know when you're getting close to a limit.
I broke my elbow last year (in a very minor way but still), when I was in the A&E the doctor told me to keep moving it and that I wouldn't be able to move it in a way that would affect negatively affect recovery. Within about 10 days it was markedly better and within 21 days I was back riding my bike, and now a year later as far as I can tell it's as good as new.
I didn't need physio or anything, the doctor just told me to keep using it as normally as possible.
>What defines optimal load?
Uncomfortable but not painful, just like pretty much everything else physiology-related in life.
> I think these are things that have to be considered for medical protocols
What makes you think those things haven't been considered?
The comment you replied to said, "the new guidance is..." I took that to mean those things have been considered.
Optimal load is right before it starts hurting. You progressively load, and when it starts hurting you unload. Your body will send pain before there is damage to be done.
Edit: in fact some discomfort or right kind of pain is good. Else you give to atrophy.