Cullen, who joined Charlton in League One on loan from Premier League club West Ham in the summer transfer window, dislocated his shoulder during the match against Walsall on Tuesday.
Gutted to have dislocated my shoulder in what was a great win and team performance against Walsall on Tuesday night. I have undergone surgery and I’m already on the road to recovery and… https://t.co/3oZYAz8jlU— Josh Cullen (@JoshCullen) November 9, 2018
Cullen was doing well at Charlton and was progressing nicely, and the long-term injury will come as a blow for the West Ham-owned midfielder.
Charlton manager Lee Bowyer has suggested to South London Press & Mercury that the 22-year-old will be out of action for three or four months.
There is nothing that Cullen can do now expect recover and hope that he comes back stronger.
Charlton are sixth in the League One table at the moment and are aiming to finish in the automatic promotion places.
As for West Ham, the Hammers are aiming to finish as high as possible in the Premier League this season.