Surprise Conclusions From NFL Shoulder Study

In the National Football League, shoulder dislocations occur less frequently than subluxations, but come with more time loss, according to a new study.

In the study, “Epidemiology of Shoulder Instability in the National Football League,” published on May 4, 2021 in The Orthopaedic Journal of Sports Medicine, the researchers conducted an epidemiologic study on shoulder instability in the NFL between 2012 and 2017.

“Shoulder instability is a common and potentially debilitating injury among collision sport athletes that can lead to long-term damage of the glenohumeral joint. Limited data exist regarding instability among elite athletes in the National Football League (NFL),” they wrote.

The researchers collected data from the NFL’s injury database on shoulder instability injuries that resulted in missed time. The injuries were classified by type, direction, timing, setting and mechanism. They determined median missed time for the different types and directions of instability. Incidence rate for game-related injuries and the relationship between player position and instability directions were also determined.

Over a six-year period, 355 players had 403 shoulder instability injuries that required missed time. More than half of the injuries happened during a game and 85% were a contact injury.

The overall incidence rate of game-related instability was 3.6 injuries per 100,000 player-plays and was highest during preseason (4.9 per 100,000 player-plays). Seventy percent of the injuries were subluxations while 30% were dislocations. Another 32% were labeled as unspecified events.

Of the dislocation injuries, 75% were anterior. The subluxation injuries were more evenly distributed between anterior and posterior directions (45% vs. 52%, respectively). Dislocations, however, were associated with more missed time than subluxations with a median of 47 missed days compared with 13 missed days.

The researchers also report that quarterbacks and offensive linemen are more likely to experience posterior shoulder instability (73% and 53%, respectively) while other positions were more likely to have anterior disability.

“Shoulder instability is a common injury in the NFL and can result in considerable missed time,” the researchers wrote.

“Dislocations occur less frequently than subluxations but lead to greater time lost. While most dislocations are anterior, more than half of subluxations are posterior, which is likely the result of repetitive microtrauma to the posterior capsulolabral complex sustained during sport-specific motions such as blocking. The risk of instability varies by player position, and position may also influence instability direction.”