I think you should take the kitten to a vet right now. If there's a way to fix I think it is better to do it now before the whole body posture will get twisted because of it.
my kitten had twisted back legs badly when it was born, it had me so worried. so I would massage them one at a time and gently stretch them while doing it. The day it turned 5weeks it just got up and walked normal it was so amazing to see , but of course the kitten was very wobbly, which is normal, but try and keep the kitten on carpet so it can learn to walk. there's no need to take it to a vet, it will just cost you money.
That's a good idea. Any specific advice about the massage?
If you warm the leg first it will help loosen the tendons so you don't accidentally hurt the kitten. Be gentle, and as your are massaging the leg stretch it into a normal position but only as far as it will go without resistance. I would say do this three times a day at least... all though I have read you can do it as many as ten times a day. If by five weeks when the kitten is learning to walk the leg(s) twist under the kitten's weight bracing might be required. ^.^ I recently found two kittens (and their moma) the kittens both have twisted hind legs, they are all ready walking age or really close but I am trying to work with them and get their legs into a normal position so I can place them with a loving family.