Perhaps a good place to start, without re inventing the wheel, is to see how your players get by with out a healer....and no access to healing magic such as the cure spells, remove disease, lesser restoration, Restoration, Regeneration, Heal, Breath of life...Raise dead etc.
See what happens with the crippling effects of disease and poisons, as they do ability damage.
Perhaps one way you could introduce the "arrow through the knee" Is to have Ability Drain.
Yeah the wizard may have survived the disease, but his constitution was chewed up. It dropped from a lofty 12, to a lowly 8. Now he has to catch his breath all the time....and he cant take nearly the punishment he used to be able to....(lower hit points). Oh have we forgotten, He now is more likely to get sick ( lowered saves because of lower con).
How about a critical hit doing ability damage......yeah his blade got buy my guard and he hamstrung me......now I need to get by with a crutch. ( lowered movement, and a dexterity lowered from a 14 to a 7)
I don't know, that might be a good place to start.
I hope this helps.