Cowboys defensive end Marshawn Kneeland posthumously diagnosed with stage 1 CTE, family says it offers context

Former Dallas Cowboys defensive end Marshawn Kneeland has been diagnosed posthumously with stage 1 chronic traumatic encephalopathy (CTE), a diagnosis disclosed by the family through the Concussion and CTE Foundation. The news arrives months after Kneeland died by suicide in November 2025 at age 24, and it adds to a growing body of post-career research that links repeated head impacts in contact sports to degenerative brain disease.

According to reports tied to the announcement, researchers at the Boston University CTE Center found evidence of CTE at stage 1, which is the earliest stage in the commonly used four-stage system. The Concussion and CTE Foundation said the diagnosis was made after death, consistent with what doctors and researchers have emphasized for years: there is currently no way to diagnose CTE definitively while a person is alive, because the condition is identified through neuropathological examination.

The family’s statement stressed that the diagnosis does not change the tragedy of Kneeland’s passing, but it is meant to help the public understand potential struggles faced by athletes after years of high-impact football. The Boston University CTE Center leadership, as quoted in coverage of the announcement, has said it is “not” surprising to find CTE in athletes who die before age 30, and that improved protocols and equipment have not eliminated the risk for everyone.

CTE has been described by medical organizations as a neurodegenerative disease associated with repeated traumatic brain injury. In the stage 1 category, the CTE Society’s descriptions cited in coverage include possible short-term memory problems and mood or behavior changes. In other words, the diagnosis is not presented as a single-cause explanation for any specific life event, but as a clinical finding that may help interpret patterns that are difficult to see in the moment.

Kneeland entered the NFL as a high-level prospect, selected by Dallas in the second round of the 2024 NFL Draft. With the Cowboys, he was in his second professional season when he died, and reports ahead of the CTE announcement noted that he appeared in 18 games for the team. The span of his career was brief, but the research conversation around him mirrors the wider debate about how football impacts long-term brain health and mental wellbeing.

The CTE diagnosis also lands amid ongoing scrutiny of contact-sport safety, where concussion protocols, baseline testing, and rule changes have been designed to reduce short-term injuries. Researchers and advocates have argued that these efforts, while valuable, do not fully address the longer-term risk created by cumulative sub-concussive hits and repeated head impacts. That perspective has been part of the message in multiple public discussions tied to posthumous CTE diagnoses.

For the Cowboys, Kneeland’s death had already prompted renewed attention from fans and the broader football community. The added detail of a stage 1 diagnosis is likely to deepen those conversations, particularly around awareness and support for mental health issues that can be present in athletes even when no single diagnosis is available.

As the story develops, teams and leagues will continue to balance two realities: CTE can only be diagnosed after death, and the presence of CTE does not automatically map onto any one symptom or outcome for an individual. Still, the Kneeland announcement is another data point in the public record that the NFL, and football culture more broadly, will have to address alongside medical research and player welfare efforts.