Dallas Stars center Mattias Janmark will have knee surgery and be out of action for five-to-six months, the club announced Friday.

Stars general manager Jim Nill revealed Janmark was born with osteochondritis dissecans, a joint disorder that causes cracks to form in knee cartilage and bone.

The 23-year-old forward, who was seen walking on crutches at Stars practice Thursday, joins a slew of teammates recovering from injuries in the preseason, including Tyler Seguin, Jamie Benn, and Ales Hemsky.

Janmark collected 15 goals and 29 points last season in his rookie campaign.

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