David Chao, MD: What Is Causing All The ACL Tears?

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There were seven confirmed anterior crucial ligament (ACL) tears after this brutal NFL injury week: Saquon Barkley, Courtland Sutton, Nick Bosa, Solomon Thomas, Bruce Irvin, Tavon Young and Marquise Blair. Many are questioning if the lack of preseason games is to blame.

The answer is complex.

There have actually been fewer ACL tears so far this season compared to most other recent years. There have been 19 ACL tears this year league-wide so far through Week 2  and the league average the last 5 years during the preseason alone is 25.

Ben Volin on Twitter “ACL and MCL tears were down in 2019, though NFL chief medical officer Dr. Allen Sills says “we don’t know why they went down,” with a deeper look needed into the data” twitter.com

ACL can be considered an acclimation injury as tears happen at over twice the rate in the preseason versus in the regular season. Consider a six-week training camp and an average of 25 tears gives us a rate just over four per week. Across a 17-week regular season, the average of just under 30 ACL tears gives us a rate of under two per week.

The spike of ACL tears from this past Sunday is in part bad luck but in part seems to be the shifting of the higher rate of preseason ACL tears into the regular season. Given the lack of an offseason program, preseason games and live practice time, it actually lowers the number of ACL tears for training camp but there seems to be a shift into the early regular season.

Even with the spike in Week 2 of ACL tears, balanced against a relatively healthy Week 1 that puts us at the preseason rate of about four per week. With the pandemic altered training camp and lack of preseason games and practice, the season so far has us headed towards a lower than typical total of ACL tears so far.

There is a small sample size so no firm conclusion should be drawn but the evidence does not prove that lack of preseason games has led to an overall increase in ACL tears.

Written by Dr. David Chao

David Chao, MD -- known digitally as Pro Football Doc -- is an expert contributor for Outkick. Chao spent 17 seasons as the team doctor for the San Diego Chargers (1997-2013) and is part of the medical team at OASIS in San Diego where he treats and specializes in orthopedic sports injuries, working with high-profile professional athletes from the NFL, NBA, and MLB.


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  1. I’m glad you wrote something about this. I was genuinely curious what you thought about it. NOW, I would love to see you write a piece on baseball pitcher injuries and how it is becoming an epidemic. Chris O’Leary on Twitter has tried his best to cover this epidemic, but no one wants to listen to him. I am one who believes his theory that pitchers are being taught to throw in a way (similar to how Tommy John threw) that increases the movement on their sliders, curves, etc. And because they are being taught these mechanics, they are becoming more susceptible to elbow/shoulder injuries. Hell…. they are becoming more susceptible to blood clots as well because of it. Sadly most baseball analysts and coaches only think “pitches thrown” and “innings pitched” are the root cause of all these injuries. It’s going to ruin MLB. I’m a Cardinals fan, and I’m already fed up with the fact that we have hardly no starting pitching and that’s primarily because our best starting pitchers are always hurt nowadays. It’s turning me into less of a baseball fan.

  2. I do wonder if a preseason saves star players from injury vs the average NFL’er or guy trying to make a roster. How many stars or players of significance have been lost in the first 2 weeks vs what is normally lost int he preseason?

  3. How much of it is just wear and tear of the modern day athlete? These athletes start vigorous training at an early age. Saquon Barkley is on record claiming that he can squat 650-700 lbs, clean 400 lbs. These guys have crazy training regiments. Knowshon Moreno supposedly doomed his career training CrossFit. These guys are making cuts and other athletic moves often on turf with these huge legs. Maybe athletes have reached a climax to where their knees are less able to take the constant stresses?

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