... the donor's orientation concerns the possibility of getting HIV or AIDS in a blood transfusion
Ironically, lesbians had the lowest instances of HIV, so getting blood or transplant tissue from a gay female would be safest.
AIDS spread mainly through the male gay community through male homosexual contact, then to heterosexual females through heterosexual contact with an infected male, then to heterosexual males through heterosexual contact with an infected heterosexual female.
Homosexual females who keep straight on their relationships (ie, only having sex with other homosexual females) would be the safest from infection. Not only would it be more difficult for AIDS to enter the lesbian community, but it would also be more difficult for it to spread.
So then "gay knees" from a lesbian would be the safest bet for avoiding catching AIDS through the transplant. But then we have already established that there's no such thing and that the knees would be artificial.