I'm glad you were able to get someone to look at her.Update - we took her to a wildlife centre last night for someone to look at her. Turns out she has a dislocated knee cap it has been strapped up to try and put it back in place, but it's looking unlikely she will be able to make it through.
Thank you everyone for your help and suggestions
Sounds like slipped tendon which can be very hard to correct. Hopefully the splinting will be a success.
Please do let us know the outcome. Sadly, sometimes it doesn't go the way we want it to.