Vet at FirstVet answers:
If your cat cannot weight bear on one of its limbs, or if it seems to be in a lot of pain, refuses to move, or does not want to eat or drink, you must seek emergency veterinary care.
If your cat can support its limb, but is otherwise its normal self, you can wait to book an appointment with a vet. Carefully feel through the affected leg for any swellings or wounds. If you are unsure if the leg is swollen you can compare it to the other leg. It is important to keep your cat indoors while it is lame. If you find any swellings and your cat does not improve within a day or two you should book an appointment for a veterinary examination. Cat bites are a common cause of lameness in outdoor cats.