The NFL’s Chop-Block Rule Change: Does It Prevent Knee Injuries in Defensive Players?:

Background:The chop block, a football maneuver in which an offensive player blocks an opponent around the thigh while another offensive player engages the same opponent above the waist, was declared illegal by the National Football League (NFL) before the 2016-2017 season. Chop blocks have been hypothesized to be associated with medial collateral ligament and anterior cruciate ligament injury, especially in offensive/defensive linemen.Purpose:To quantify the impact that the chop-block rule change had on the incidence of knee injuries to defensive players in the NFL over 4 seasons (2014-2018).Study Design:Cohort study; Level of evidence, 3.Methods:NFL injury data for all defensive players from regular-season games played from 2014 through 2018 were collected. For this study, all knee injuries were attributed to competitive game play. Injury rates were reported as the number of injuries per 1000 athletic exposures (with 95% CIs).Results:A total of 256 games were played during the 2014-2015, 2015-2016, 2016-...