My Elvis had a similar thing, though it was never diagnosed as this, the vet just said he was deformed in his back legs and should be pts. He was about two weeks when it was first noticed.
Me and another nurse from the hospital shared duties in handrearing him and carried out physio by just manipulating his back legs and trying to strengthen them regularly and they did resolve themselves. He has never been a great jumper and not as athletic as my other cats, but other than that he is perfectly healthy.
The tape solution does seem to be very effective from those websites, definitely worth a go I would think.
