Dallas Cowboys' Marshawn Kneeland had stage 1 CTE, brain study finds

Former Dallas Cowboys defensive lineman Marshawn Kneeland was diagnosed with stage 1 chronic traumatic encephalopathy (CTE) following a postmortem examination of his brain, according to researchers at Boston University's CTE Center.

The diagnosis was made after scientists analysed brain tissue following Kneeland's death in November 2025 at the age of 24.

According to the researchers, stage 1 is the earliest of the four stages of CTE and is commonly associated with symptoms including headaches and difficulties with attention or concentration.

“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 the centre's director, Dr Ann McKee.

In a statement, Kneeland's family said the findings provided “important context” to some of the challenges he had been experiencing.

“We share this information to help people understand what NFL and other high-contact sport athletes might be struggling with,” they said.

“We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life.”

Kneeland was selected by the Cowboys in the second round of the 2024 NFL Draft and played 18 games for the franchise, including four starts, after previously starring at Western Michigan University.