Winter has been playing for the Lions in South Africa's Currie Cup

Dowson, 25, has been ruled out for the rest of the season after rupturing a biceps tendon last month.

Winter has played for the Cats and the Sharks at Super 14 level as well as captaining the South Africa A team.

"His leadership and experience will be most welcome over the next 18 months," said rugby director John Fletcher.

"We have utilised our global scouting network with Marius Hurter in South Africa and Ross Nesdale in New Zealand, allowing us to react and bring over quality players who they know first hand.

Phil is a very strong character and I'm sure he can come back from this Newcastle rugby director John Fletcher

"All the reports on Russell have been very positive, both from a rugby and a character viewpoint, and we look forward to the leadership and direction he will bring to the back row."

Newcastle, who have now signed three forwards in the last month, made the move after Dowson picked up the injury against Wasps on 15 October.

Dowson missed most of last year with a serious neck problem.

"Having put in a long and demanding rehab after his neck injury, Phil was getting back to some fantastic form," added Fletcher.

"Phil is a very strong character and I'm sure he can come back from this.

"Everyone at the club feels for him especially after what he went through last season."

Dowson, who played for England in the Churchill Cup last year, had a pioneering operation to fit an artificial disc in his neck last November.

He returned to action this season, playing five Premiership and two EDF Energy Cup matches.