It will happen to you one day D_S it doesnt matter how fit you are in your younger days the more sport ect you do now will catch up with you. Im temp P3LE at mo after braking my ankle playing LAD Craftsman Cup football I think P3 is temp side of it and LE is lower body. It does go up to P7 and med centre can tell you grades
I have heard of one of my JNCO's being able to transfer but individual cases are dealt with by SPSO's and RCMO if you can fullfill that roll.
It - and indeed all of the other med cats - can be temporary or permanent depending on what's broken or infected.
P3LE is typically given to someone who's picked up something that requires regular meds or broken something such that it isn't back to the way it was but who can still do the job. The phrase used is "lines of communication" as opposed to "forward" and a doc has to review the med records to check there's nothing in theatre that would aggravate the condition. I suspect it's far more of a career stopper for a 20 year old infantry Pte than a 40 year old AGC WO2.