Let me bring up a couple of points here.
Crippling Strike as a physical effect cannot be cured through any means besides simply sitting there.* If you have backstab listed as an affect, you have been subject to a
crippling strike, and your strength has been lowered. Like most other
affects, this will go away with the passage of time. This being a non-magical
affect, magic can not remedy it.
And its duration is absolutely ridiculous for how much it reduces strength. I'm suggesting it be nuked down to a max of eight to ten game hours, because let's face it. You get hit with Crippling Strike as an Abjurer, Ranger, Thief, (dexterity) Fighter or Bard, you're not going to be fighting again for a few real life hours. I got hit with a -4 to strength, personally, which gimps my character fairly well. I'm not sure if it's because it stacks, which it might still, but that's the penalty my character got.* Ability points lost to crippling strikes return slowly on their own at over
the course of a couple of days.
To add to my point, I'm going to throw out an example. You're a Bard, you're not strength-based much at all, you might have full leather or studded leather armor on and some stuff tucked away in your bag(s) as well as your weapon in its container. A Thief NPC backstabs you, you lose four strength and are suddenly at a massive disadvantage because you've just lost two points of damage and now you're at medium encumbrance for the duration unless you stash your armor with your horse or cart and go naked or in cloth. Your options are pretty much either to idle or go attempt to find some casual RP for four real life hours, if the helpfile is correct.
You can't do anything about it, you can't raise your strength to compensate like most Wizards and Clerics could, you're not hardy like a Fighter and able to just tough it out for a couple more small skirmishes (even though Fighters suffer similar detriments, especially light-armored dexterity-based Fighters). You're simply out of luck until it wears off.
Honestly, making it removable by certain high-power healing spells would suffice, but if not that, please at least reduce its duration to eight or ten game hours. It's bad enough that it removes four of your strength points with all of the detriments that come with that, but having it last four real life hours? Come on, nobody deserves to have to sit in the corner for two (or more) IC days because they're suffering from being jabbed in the muscles with a knife.