I feel stabbing / shooting pain in the back of my knee and lasted a minute or so. i had knee replacement 5 mos ago?

Contact the provider: Sounds like a reason to contact the surgeon/provider if you can wait till Tuesday. If it's too painful you might even go to Urgent Care or an ER - but a follow-up exam to the surgery seems appropriate to do ASAP and your surgeon has the best knowledge of what that pain may relate to. Don't worry - just call ASAP. I hope it goes well.

Not enough to advise: I do not have enough information to specifically advise you; however, if the pain recurs I strongly suggest seeing the orthopedic surgeon who performed the knee replacement for definitive diagnosis and treatment as soon as possible. Best wishes.

See physician: if this pain is ongoing and recurrent please check with your physician