February 2006: High Risk of New Knee Injury With Previous ACL Injury

Let me start off by saying that I love rookie defensive tackle Dominique Easley. I love, love, love what he brings to the table and should he remain healthy he's everything that the Patriots defense has been missing over the past half decade.

But let's just say I was intrigued. The Patriots will be leaning heavily on Easley and tight end Rob Gronkowski, as well as grizzled veterans Vince Wilfork (albeit his is an achilles injury) and Tommy Kelly. I wanted to see how worried we should be about ACLs.

We've seen plenty of players come back at an elite level after surgery to their ACLs. Adrian Peterson dominated the league with a historic season. Tom Brady came back. Wes Welker came back. Darrelle Revis in 2012. If the Patriots sign tight end Dustin Keller (and I expect them to), that's another one for the list.

ACLs have historically been a banner of death for a player's career, in the fact that a) they might never return, and b) no one ever expects them to return at their prior level of play. This perspective has changed recently, due to new studies and surgery (they found a new ligament in the knee in November of 2013. Whodathunk) and we've seen teams become more willing to utilize players with an ACL injury in their history.

So take this study from February 2006 with a grain of salt. Things have changed since then. iPhones weren't even a thing this far back. But historically, players who have injured their ACLs have a much greater chance of reinjuring their knees over the next two years.

This is a study from Sweden, where they studied a different type of footballer, but it seems to be valid after reading through it.

Essentially, they followed 310 soccer players, some with prior ACL injuries and a control group without a history of ACL injuries, to see if those with ACL injuries are more likely to be injured than those who have not.

Their conclusion?

The risk of new knee injury, especially overuse injury, was significantly increased on return to elite football after ACL injury regardless of whether the player [ie: general injuries] or the knee was used as the unit of analysis.

So not only were these players more likely to reinjure their knee, they were more susceptible to injuries in general. In the ACL injured group, "70% [of the new injuries] affected a limb with a previous ACL surgery."

The study references another piece of research from the 90s that concluded:

The strongest risk factors [for injuring an ACL] were a player history of anterior cruciate ligament reconstruction either in the previous 12 months or before the previous 12 months.

To translate their research, they mean that the highest risk for injuring your ACL is if you had surgery performed on that knee in the past year. The second highest risk is if you had ACL surgery in the year prior to the current- the injury was just as likely to affect the non-surgically repaired knee as it was the previously injured knee.

In other words, you're most likely to injure your ACL if you had recent surgery on it. If it's been 1-2 years since the surgery, you're still more likely to injure your ACL than someone who hadn't had surgery on their ACL, but you're just as likely to injure your other ACL.

I sincerely hope the times have changed. I would love to see some more recently studies on this topic. I would love to see Dominique Easley win rookie of the year and Darrelle Revis and Rob Gronkowski win defensive and offensive player of the year, and Tom Brady win MVP.

But the data certainly goes against this. The Patriots are playing the odds that everyone can recover and remain healthy. Easley is going to be limited during the off-season. Tommy Kelly and Rob Gronkowski are going to take their time back. Revis is hopefully going to be another year stronger as he'll be two years removed from his surgery this upcoming October.

Let's hope the odds are in the Patriots favor.