Rhino
It depends, in the UK we are hapy to use donor blood for patients undergoing TKR, we don't tend to donate our own blood but it is becoming to be introduced.
When I worked in orthpaedic some patients needed a transfusion in thetre and after some didn't, likewise some had a soinal block and some had a GA.
I think it will depend on what your surgeon sees fit, my OS always gives 2 units of blood after knee replacements but my last one didn't believe in it unless it was absolutely essential.
Best to ask your surgeon when signing your consent form.