0 - Pain free1 - Very minor annoyance - occasional minor twinges.
2 - Minor annoyance - occasional strong twinges.
3 - Annoying enough to be distracting.
4 - Can be ignored if you are really involved in your work, but still distracting.
5 - Can't be ignored for more than 30 minutes.
6 - Can't be ignored for any length of time, but you can still go to work and participate in social activities.
7 - Makes it difficult to concentrate, interferes with sleep You can still function with effort.
8 - Physical activity severely limited. You can read and converse with effort. Nausea and dizziness set in as factors of pain.
9 - Unable to speak. Crying out or moaning uncontrollably - near delirium.
10 - Unconscious. Pain makes you pass out
Then we writers fill in the categories with synonyms. For example
I went to my old thesaurus, 377: physical pain, and found: pang, smart, nip, pinch, tingle. Then I thought of: itch, tweak, gripe, discomfort, tightness, swelling, sting, bunchedness (eg of muscles before they cramp)
Next you could do metaphors and similes, though in my experience they are easier to think up during the actual writing, when you have the context in front of you.
I'm not going to do more than that here. I believe that a chart you do yourself will suit your own writing style. Secondly, doing one yourself you'll have a better memory of what is in it and that it exists somewhere in your notes.
It's very worth while doing up a chart, as you'll probably use it quite a bit if you're having characters getting themselves into physical, and mental, troubles.