The Cornishman has put a string of impressive performances for the Blades, but their board will only sanction a permanent move if they get promoted.
"Wayne's deal has come to an end, and he has had some great games for us in a spell when we needed a left-back," explained Blades boss Neil Warnock.
"We couldn't have kept Wayne until the end of the season, so we looked at other options and brought in John Curtis. Wayne enjoyed his spell here and thanked us for having him."
Despite his form at Bramall Lane Quinn is unlikely to be able to force his way back into the first team squad at Newcastle, especially with Olivier Bernard in the form of his life.