Saints have eased their second row shortage by signing Scotland lock Tom Ryder on a deal until the end of the season.
Ryder, who has two caps to his name, joins from Glasgow Warriors and will be available for selection immediately.
He will help cover for Courtney Lawes, who is not expected back until the end of February after ankle surgery, and Christian Day, who is on international duty with England. James Craig has also been missing due to tendonitis.
No.8 Sam Dickinson has been playing lock in recent weeks, while flanker Calum Clark was also foced to cover the position at Sale earlier this month.
Ryder will bring plenty of experience, with the 29-year-old having made 87 appearances for Glasgow since 2010.
And Saints boss Jim Mallinder said: “We have a number of significant injuries in the second row, and Tom’s experience and quality will be useful to have around the club over the next few months,” he said.
“We have difficult Aviva Premiership matches and a Champions Cup trip to Clermont Auvergne, and we’re confident that Tom will be able to contribute fully.”