what happened to my crayfish?

[yfz]

I've had a yabby for a few months, size is about 2.5in, everything seemed to be normal, she was very active, and then a few days ago it looked like the right back leg was deformed/bent above the middle of the leg and the two legs immediately in front of it seemed to not be functioning correctly. To walk around, she curls her tail as a peg-leg and often times flips over in the process. In my 20g-long tank with it I have a bamboo shrimp, 5 cherry shrimp and an amano, several pieces of bog log, plastic plants, course gravel, and a hollow log she uses to hide in. The water is clear, I vacuum weekly and the other critters are doing well. temp is at 76deg. I thought maybe she got her rear leg caught in a piece of bog log in one of her climbing expeditions, but it doesn't explain the other two non functioning legs in front of it. This is my first crayfish / lobster and I can't figure out what happened to her or what I should do differently for her besides looking for any small pockets in the bog log.

[SmokeyCFH]

I wouldn't worry too much, any number of things could have happened to it, but once she starts getting bigger she'll molt her shell and the legs will be back to working order. I've had a number of crawdads, i've watched them twist each others claws off, rip legs off and they've all been fine until my big fish got a taste for the tails.

[CGQ918]

* If it is alone it will be 100% ok. Make sure you put it's food near it.

* When it molts, the broken legs will be replaced by fully functioning ones.