The diagnosis was delivered by an independent spinal trauma specialist after the superstar forward complained of swelling in the C1-2 joint of his neck.
Crosby has been out since Dec. 5 with concussion-like symptoms. He was also diagnosed over the weekend with a neck injury.
The specialist, Dr. Alexander Vaccaro of Philadelphia, said the soft tissue damage could be causing some of Crosby's symptoms, which can be similar to those of a concussion.
Doctors believe Crosby is safe and that his injury is treatable, the Penguins said.
They reiterated the 24-year-old will return to the ice when he is symptom-free.
Crosby played only eight games this season before being knocked out of action by a hit from Boston's David Krejci.
He had missed 10 months before that due to a concussion.