can i do alignment on front wheels only? or all 4 wheels must be done?

[bosanci28]

hi,
2001 bmw x5 4.4l sport

for some reason the tire on passenger side front (the outside part of the tire)
is going out ,almost to the wire...what i am thinking is from the "tow" maybe the wheel is not straight up,i guess.





so today i am going to change it,

(all other wheels/tire are fine)

now ,do i have to do alignment on only the front 2 wheels or all 4 wheels must be done?

thanks,