​Kieran Tierney is set to be out of action until well into 2020 after Arsenal confirmed that the defender dislocated his shoulder in the 3-1 victory over West Ham on Monday night. 

Tierney was making his fifth league appearance for the Gunners at the London Stadium, but the ex-Celtic man was forced off the pitch after half an hour when he fell awkwardly on his shoulder. 

Kieran Tierney

The 22-year-old looked in severe pain as he was substituted, and Arsenal have confirmed on their ​official site that the full-back has suffered a dislocated shoulder, and is set for another spell on the sidelines.

The length of the layoff is still unknown however, as the club announced that Tierney is 'currently undergoing further assessment and investigations', which will involve a decision on whether or not the injury requires surgery.

The young defender joined ​Arsenal from Celtic in a deal worth around £25m in the summer, but his debut was delayed after he underwent a double hernia operation at the end of May 2019. 

Tierney was a key part of the Scottish champions' defence, the Hoops completing the 'treble treble' last year – winning all three domestic competitions for three successive seasons. 

Kieran Tierney,Felipe Anderson

This blow comes as a great concern to Gunners fans, whose defence has been ravaged by injury all season. The north London club have had a torrid time of late, and they sacked manager Unai Emery at the end of November following a run of seven league games without a win. 

Arsenal legend Freddie Ljungberg has taken temporary charge in the dugout, and the Swede oversaw his first win as interim boss against a struggling ​West Ham side. 

The Gunners face Standard Liege in the final match of the Europa League Group F, with qualification to the knockout rounds all but sealed. 

Ljungberg will be without Tierney, Hector Bellerin, and Rob Holding through injury for the midweek fixture, whilst Shkodran Mustafi is suspended after picking up three bookings over the course of the group stage.