The visitors passed and probed and went close as Thomas Vermaelen headed wide from a Tomas Rosicky cross, before Reina tipped a Theo Walcott free-kick round the post.
The Scunthorpe midfielder picked himself up after being fouled and bent a 20-yard free-kick round the wall, with keeper Dudu Aouate managing to get a touch before the ball hit the corner of the net.