Background Concussion is one of the key player welfare issues in rugby union. Independent Matchday Doctors (IMDDs), supported by live video feeds, were brought in to elite men’s rugby union matches in England over the 2019–2020 season to support the in-match off-field head injury assessment (HIA) process.

Objectives To determine whether rugby union players diagnosed with a concussion post-match could have been removed for an in-match off-field HIA.

Design Prospective cohort study.

Setting Twelve professional rugby union clubs in the highest league in England.

Participants Professional male rugby union players.

Outcome measures 1) Number of concussions diagnosed post-match, where no in-match off-field HIA was performed.

2) The proportion of these that were ‘tagged’ in-match by the IMDD on the ‘Hawkeye’ live video system as events with the potential to result in concussion.

Main Results Twenty-five concussions were diagnosed post-match (21% of total concussions). In 20 instances, an IMDD report and match-specific Hawkeye library were available for analysis. Of these, the IMDD reported a potentially significant incident in 12 (60%) cases, and a potential incident was ‘tagged’ on Hawkeye in 13 (65%) of cases. In 6 cases (30%), nothing was highlighted in either the IMDD report or on Hawkeye, and in 9 cases (45%) there was an incident highlighted on both. Common features observed in the ‘tagged’ video clips include: players staying on the ground after contact for longer than other players; players steadying themselves on their knees before standing; subtle gait changes; and players grasping the face after contact.

Conclusions Over 20% of concussions were not diagnosed in-match, and over half of these were ‘tagged’ as events with potential to result in concussion. Governing bodies should consider these video features when setting the threshold for HIAs. Optimising this process could help minimise the risk of negative health outcomes in players.