Understanding differences in return to play in different sports, after an ACL tear

Posted on October 19, 2016

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In NFL players,

  • 63% got back on the field after anterior cruciate ligament reconstruction
  • For wide receivers and running backs, for those who return performance is decreased by a third (getting back on the field is not the same as returning to the same level of play)

In NHL players,

  • Those who tear their ACL play an average 2.8 years afterwards, compared to a control group which played 4.4 more years
  • For wings and centers, games played per season goes from 71.2 to 58.2
  • After injury, points per season goes down by 61% the first season of return, and still by 43% in the second season of return
  • Nearly 20% of players either couldn’t return to play at all, or couldn’t return for a full a season.

In soccer players,

  • 89% returned to training and participated in a match within 12 months
  • In a different, more recent study, 72% made it back within 12 months. 85% of those who made it back to play, got back to same level of play.
    • In a sample of 100 people, that would mean 61% made it back to the same level of play.
  • 20% of ACL injured players were still playing after 3 years, compared to 50% of non-injured players
    • “None of the 24 elite players with a ligament injury played soccer on the same level as before the knee injury”
    • (This study is a bit older, which could explain the differences i.e. our ability to handle ACL injuries may have improved.)
  • 77% of MLS players made it back, with no decrement in performance
  • 65% are still playing at the top level after three years

-> This may be an interesting way of assessing how elite MLS is relative to places like Europe. Rather than MLS doing something different rehab wise, the level of play may be lower enough that if you can get back on the field, you can be just as good.

In NBA players,

  • 22% didn’t return to play at all after ACL reconstruction
  • In those who make it back, many performance measures decrease. Field goal percentage, games played, and turnovers. However, overall performance doesn’t go down too badly.

In elite skiers,

  • In those who suffered an ACL injury, their career was 7.9 years vs 4.4 for those who DID NOT tear their ACL
  • 23% of ACL tearers got on a podium, whereas only 8% who didn’t tear it did
  • ALL of those who tore their ACL continued their career

In all the other sports we looked at, tearing the ACL was a major sign of career jeopardy. If the career wasn’t over, it was a major risk factor for performance detriment, and a lessening of your career.

But in skiing, tearing the ACL was a sign of career improvement!

The order of the sports above is on purpose,

  1. Football (American)
  2. Hockey
  3. Soccer (football to the other seven billion people)
  4. Basketball
  5. Skiing

What we have above is in order, which sports are the most intense on the ACL.

The most obvious element of football compared to these other sports is someone is regularly diving at your knees. Hockey checks up high, soccer tackles at the shins (they wear shin guards, not knee), there is no hitting in basketball or skiing.

Another way we can understand football as being the most intense is by looking at play duration. A football play might be four seconds. It’s all out effort. You’re going from zero to as fast as possible. This is like a car. If you gently rev it up to 60 miles per hour, compared to flooring it, it’s obvious which is more stressful to the car. If you’re in a fast enough car, it’s obvious which is more stressful to you too. You don’t get knocked back in your seat gently moving from 0 to 60. You do when you go 0 to 60 in three seconds.

Hockey guys love to think their sport is so tough, tougher than football, and they’re always delusional on this.

-Hockey is very intense, but in 45 second bursts or so. You can’t be as intense in 45 seconds as you can in less than 10 seconds. Just like how you can’t lift in 10 reps what you can for 1 rep. This is why 400 meter runners aren’t as fast or muscular as 100 meter runners.

-Hockey goes 82 games a season. Football only goes 16, and most can’t even make it a full season with only that amount.

-In four years of that NHL study, only 46 ACL tears were reported. This is about how many happen every season in the NFL.

The other issue with hockey is by wearing skates, compared to cleats, the knees aren’t as vulnerable. Getting a foot caught, having someone fall on your leg and it can’t move because you’re in cleats, is how many ACL tears happen. This doesn’t happen with skates or on ice. Because your leg can slide out, it’s harder for the knee to buckle.

Hockey and soccer are close. Hockey is no doubt more intense, but soccer involves slide tackling, and the cleats per above. Anecdotally, I’d go soccer. However, it seems per team per year, hockey has more ACL tears. So we’ll go with hockey.

Basketball is hard on the knees, but not in an ACL manner. Basketball is hard in a “pounding the pavement” type manner. (Much harder than these other sports.) It’s not nearly as hard on the knees compared to say football, in a stability or intensity manner. If you’re a bigger guy, you can go a whole season and never fully exert yourself. (Dwight Howard.)

Certain players, like Russell Westbrook, or Dwyane Wade back in the day, that’s different, and they’re very rare in how they play. But on balance, basketball players aren’t exposing their knees to the type of trauma these other sports are. In eleven seasons of the study referenced, only 31 anterior cruciate ligament surgeries were identified.

-> However, if you’re female, basketball can be hellish on the ACL.

Finally, with basketball, you can modify your game to a degree you cannot in other sports. You can become a post player, focus on rebounds, passing, three point shot specialist, do a multitude of easier-on-your-knees things. You can modify your minutes as well. These are much harder to do in other sports. I’m not sure I’ve ever seen a guy in hockey lazying it up. In basketball you can change your game once you hit ~30, and keep going. You can’t do this as a running back or wide receiver. Instead you hit 30 and you’re often given your “thank you for your contribution, grandpa.”

Now to skiing. While it is not as hard as something like soccer, skiers are still notorious for tearing their ACL.

However, the massive difference with skiing is you know where you are going when you do it. You have planned routes, planned moves. In football, soccer, hockey, basketball, you are constantly having to react to other people.

We have active and passive restraints. Active is things we control, like our muscles. Passive is things we don’t, like our ligaments. With the ACL, we have the passive ligament which helps our knee stability, but we also have muscles like the hamstrings.

ACL lachman with hamstring line

ACL and hamstrings both pull tibia (bone on left) backwards.

The more the active restraints work, the less the passive need to kick in. But when you’re having to react to others, you don’t always get the level of control over the active restraints that you want. So when they don’t kick in properly, or they’re not in time, we have the passive as an insurance policy.

When you know where you’re going, you can more easily prep your body for what it needs to do. When you don’t know where you’re going, there is only so much you can do.

It’s easier to fall on the floor if you know you’re going to fall, then to fall on the floor and not know it. You can more easily use your active restraints to ease your fall in the first case. In the second case, you’re hoping your bones can ease the fall the best they can.

When you know which direction you’re going to turn next, your muscles can more easily take over that work. When you don’t know, like when someone hits your leg, they may need help.

The more you need an ACL after it’s been reconstructed, the harder that activity will be to get back to.

  1. Because new materials are never as good as the original, when it comes to your body
  2. The first ACL had a couple decades to adapt. We’re now asking the new one to learn in a year what the old one had twenty years to learn.
  3. Psychologically, there is a level of control you have to cede when getting back to a high level activity. The more control you cede, the harder it is mentally.
    1. I tore my ACL on a grass field which seemingly doubled as a groundhog reproductive sanctuary. I can go run around like crazy on a tennis court; I can’t step on a grass field without looking for divots now. Same movements; different level of control.
  4. How many are working on this in their ACL rehab? Where they’re having to react to stimuli? Compared to how many regain their range of motion, do some strength training, then go try to play their sport again? Which would be the equivalent of saying, “Well, I’m not going to work on my range of motion or strength. I’ll just let the sport take care of that for me.” In other words, there is no building up of this reactionary skill. You’re just all of a sudden one day saying, “Hey, new knee, respond to this crazy shit.” It needs to be part of therapy, though it’s often not.

But why did the skiers come back better?

In baseball players who’ve had Tommy John surgery, many come back just as good, and some better. The best theory I’ve seen on this is after blowing your arm out, you take your body more seriously. You prehab better, you take strength training more seriously, you all in all are more committed to physical preparation.

This is likely what happened to the skiers. Despite what would seem obvious, many professional athletes don’t have much of a relationship with the weight-room. I don’t know skiing, but I’d assume they really don’t have much of a relationship with strength training. They seem to obsess over dry land jumping as much as possible / doing whatever they can to make their quads burn / how comfortable their cabin clothes are.

After an ACL injury, if you’re at all doing things properly, you’re going to have a relationship with strength training.

What likely happened was these skiers blew their knee out. They realized to get back to where they were, they needed to take things more seriously. They got much more into strength training. Strength helps everything.

They return to a sport where they could more easily control their leg musculature than other sports. (Especially in a professional setting, the skiers don’t have to worry about amateurs on the same path snow flaking on their face, bumpy snow, a patch of ice, etc.) They returned with a stronger body overall. Boom. They perform better and last longer. They also get a leg up on their competition who isn’t doing anything but skiing and sipping hot chocolate.

Which is an important point for other sports. If you’re a football player, relative to your competition, your active restraints are probably about as strong as they can get. You and everybody else already take lifting seriously. While the skiier might not have as perfect of an ACL as a non-injured person, they can make up for it by taking strength training more seriously than the non-injured person. In a football player, you don’t get that margin.

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