Initial versus Subsequent Injury and Illness and Temporal Trends Among Professional Hockey Players.

The study only included NHL players, so results may not apply to amateur, female, or other professional leagues. Data relied on publicly available reports, which do not allow for quantification of missing data or verification of medical diagnoses. Injury reporting was often ambiguous (e.g., 'lower body' instead of specific joint), leading to potential misclassification and underreporting of specific body regions. Athlete exposure was estimated based on game schedules rather than actual individual play time, which may introduce residual confounding. The data were not reported by clinicians, increasing the risk of inaccuracy in injury definitions and severity.

Do not assume the decline in head/neck injuries proves that rule changes alone caused the reduction, as visor mandates and improved concussion recognition protocols occurred simultaneously. Additionally, the increase in 'lower body' injury labels suggests that specific lower extremity injuries may be underreported rather than actually increasing in incidence.