The Republic of Ireland international, who turned 30 on Monday, has linked up with the London outfit on a temporary basis as Mark Warburton’s men look to mount a promotion push.
Hendrick joined United after leaving Burnley in August 2020 and has made a total of 27 appearances for the Magpies across the last 17 months, scoring three goals – including one, against Wolves, this term.
His deadline day switch to the Kiyan Prince Foundation Stadium means the former Derby County man could make his debut for the Rs in their FA Cup fourth round tie at Peterborough United on Saturday afternoon.
Warburton’s men currently sit fourth in the Championship table, just seven points behind league leaders Fulham.