I know some one who wants to do yoga, and they have had a knee replacement.
Im not sure what will have happened to the ligaments or what can/can’t be done in yoga postures, does anyone have any advice?
It would need to be determined what muscles were cut for the replacement before determining what can and cannot be done by the student. Have that person inquire of their surgeon and relay that information to you. From that, in conjunction with the anatomy and physiology training you received in your teacher training, you can make some determinations about what she/he can do as far as asana.
Sounds like a reasnoble way forward, thank you 