I don't think the vet is really sure what is causing it, theres a possibility that it is caused by the shock of waking up one day with a leg missing, he certainly hasn't entirely figured out that the leg isn't there as he went to scratch behind his ear on Friday with the missing leg and his head went back and the stump wiggled but he didn't quite figure out why it wasn't working. The only out of the ordinary thing is that he is doing otherwise is drinking a lot of water and drooling when he is fussed more than he used to. The thing that upsets me is that he seems to have absolutely no control over his back end movements, you can see it in his face that he just doesn't understand why he isn't going where he wants to. Sometimes his remaining back leg just seems to collapse under him as well. The vet had a good feel of both legs and he didn't twitch or anything, so if it is causing him pain, it must be sporadic and just a reaction of the nerves to being cut. He said that time may be a huge factor, it may just take him a lot longer to get used to coping.
The good thing is, he isn't in the slightest bit interested in going out now since his escapology, I think he has connected the outside with the accident now, he was terrified of the traffic outside the vets, was doing circles in his box. Mum is thinking that there is a good chance of him being a permanent indoor cat, so I have been trying to think of ways to construct some kind of activity/scratching area that is suited to a disabled cat and she is beinging grass in every so often from the garden to try and help him bring up hairballs.