Former Dallas Cowboys defensive end Marshawn Kneeland has been diagnosed with stage 1 chronic traumatic encephalopathy (CTE).
Kneeland, who died by suicide at 24 years old in November 2025, was diagnosed posthumously by researchers at Boston University’s CTE Center, according to a press release from the Concussion and CTE Foundation. Kneeland was in his second professional season with the Cowboys when he died. The press release noted that he had been playing tackle football since he was seven years old.
“Unfortunately, I was not surprised to find CTE in the brain of Mr. Kneeland, because we have found this progressive brain disease in nearly half of the athletes we’ve studied who have died before the age of 30,” said Dr. Ann McKee, director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System, in a statement.