Why is it so hard to recover from an ACL injury?

Posted on March 12, 2018


(Last Updated On: March 12, 2018)

It’s disconcerting how many ACL patients struggle to make it back to their previous activity level. Suffice to say, the majority don’t.

On one of my ACL posts, some have been unhappy with its negativity. As if I’m manipulating the statistics. However, as someone who has had ACL surgery and has made it back to their previous level of activity, along with working / seeing / knowing many who have not, I’m actually of the belief many more could make it back to what they were, with caveats. The principle caveat being recovery is very hard, but let’s break that down some.

Time commitment

I’ve hammered on this in the “Is it worth it?” post, but it bears repeating. If we’re talking doing this right, genuinely trying to get back to one’s previous level of activity, then this is a seven day a week endeavor you’re embarking on. Seven days a week for probably a minimum of the first few months.

When was the last time you consistently did anything seven days a week? Is there anything? Besides eating, defecating, sleeping?

This translates to something like seven+ hours per week. (Not including travel time to a gym or physical therapy office.) When was the last time you ever worked on something exercise oriented this many hours per week? Even if you played sports, you didn’t work on rehab this much per week. You were playing games and stuff. That’s a lot easier to stick with because it doesn’t suck / bore you as much as reading a 19th century novel, which is what rehab does.


This is a lonnnnnnng recovery. If we’re talking more dynamic sports, football, soccer, basketball, hockey, etc., best case for most is back in nine months. You almost assuredly will not feel “right” at nine months, but your knee and leg will be stable and strong enough to do these activities. How well you can do them is a different story. Getting back to previous level of activity and getting back to previous level of performance are not the same.

It can take two years for the tendinous graft to transform into a ligament.

Remodelling of human hamstring autografts after anterior cruciate ligament reconstruction


Anecdotally, people will progressively feel normal until ~18 months, when they finally feel “right.”

So we ask again, when was the last time you ever waited 18 months for something to heal? For nearly everyone having ACL surgery, the answer will be “never.” I mean, when was the last time you waited 18 months for anything???

So if you’re trying to get back to a high level of sports, it means waiting 18-24 months until you’re right again. Sticking with an exercise routine for this long. How many have ever exercised consistently for upwards of two years?

Yes, some mini breaks can be mixed in here, and it doesn’t always have to be so structured once you’re past the 9 month or so mark, but you can’t be sedentary for months and then at two years think you’ll be fine playing basketball. You’re going to more or less need to be dedicatedly exercising multiple times per week for upwards of two years. That new ligament has to be progressively adapted to the stimulus. Not thrust into the fire.

I believe the timeline of this recovery weeds out a huge amount of people in making it all the way back.

  1. People can’t stick with it. They don’t have the consistency in them. They’ve never been this patient. It’s too hard as an everyday person -job, significant other, social life, lack of resources- to do it.
  2. People give up. “Fuck it. I’ll never be normal again.”
  3. People age

By 3. we mean by the time a full recovery takes place, so much life happens, people have moved on. Most tearing their ACL will be in their teens to 20s.

Two years is an eternity for someone this age. A two year recovery can represent 10% of your life! (Don’t worry, by the time you’re nearing 30 life will feel like it’s moving so fast, you’re going to assume if you blink ten more times you’ll be in a coffin.) And life is changing much more during the ACL years than others.

Tearing your ACL junior year of high school may automatically make the decision that you’re not playing in college, because by the time you’re fully recovered you’ve missed all of recruiting and you’re in college! Once out of organized sports, as most are by their 20s, you’re unlikely to ever participate in as intense of an activity. Regardless whether you tear your ACL.

Tearing your ACL at 27 from playing rec sports, to where at 29 you’re really feeling solid again, and you’ve already moved on to being married with a kid on the way. You don’t have time for sports like you did.

Tear your ACL in the NFL and after two years you’re two-thirds done with your career. Plus, the likelihood any team is going to wait on you for that long is minimal. The team’s roster is already half new. By default you never participate in a sport as intensely again.

-> The Patriots were in the Super Bowl in 2017 and 2015. 30 players in 2017 didn’t play on the 2015 team. More than half the roster.

Tear your ACL at 29 and by 31 you can’t perform at your previous level because you’re on the other side of 30, and most can’t perform like they did in their 20s anyways.

Nothing is the same as when it’s new (but that doesn’t mean it can’t be as good)

From a biology perspective, ACL surgery is damn tough. While not a perfect analogy, I’ve heard this one before (from surgeon Robert Klapper) and it works well. If you’re outside of a pool and you cut your skin, it’s fairly easy to heal. You can clean the area up, dry it off, put a band aid on, stitch it, whatever need be.

However, if you’re in the pool and cut your skin, it’s hard to do much of anything with it. You have to come up with something besides the out of the pool modalities. Using a band aid in a pool doesn’t work.

The medial collateral ligament is out of the pool (out of the knee joint). It’s pretty easy to fix. In fact, it more often than not fixes itself.

medial and lateral collateral knee ligaments

The ACL is in the pool (in the knee joint). It can’t heal on its own, and it’s not easy to help it.

ACL anatomy with fibula

The pool is the synovial fluid, which in a sense blocks the ACL from healing. Synovial fluid is not bad stuff though. It’s like lubricant for the joint.

So you tear your ACL and the body is essentially saying keeping the joint lubricated is more important than healing the anterior cruciate ligament.

Then we need to get fancy with our in the pool modalities, as the out of the pool ones, like stitching the area together, don’t work. (Imagine attempting to stitch noodles together in a pool!) We put a new ACL in there, but it invariably stretches some. ACLs are put in extra tight knowing this will happen. Hoping when it loosens some, it’s only to a neutral position, not an excessively lax one.

The other way to make sure the graft, which will be the new ACL, doesn’t stretch would be to significantly lessen range of motion after surgery, for a while. For instance, with a patellar graft we think it takes about eight weeks for the graft to be really set, whereas with a hamstring graft it’s more like 12 weeks. So for 8-12 weeks we could lock the leg, like in a cast, so someone can’t stretch the graft.

But we all know locking a joint in one position for a long period of time causes a ton of issues. Take your arm out of a cast and it looks ruined. Sure, the arm can still heal well, but a person will possibly have lost some range of motion forever. Furthermore, with ACL surgery this is an even worse idea, as the risk for ailments like arthrofibrosis shoot up. Long story short, we’ve seen aggressive rehab protocols do better than conservative ones.

In other words, we learned what the body already knows: It’s better for the joint to have synovial flow than focus on the ACL. What’s best for the knee is not necessarily best for the ACL. What’s best for the ACL is not necessarily best for the knee. It’s tough to have it both ways.

Speed progressively matters

We’ve gotten to where ACL surgery can do a nice job for those having stability issues during low intensity activities, but when activity intensity gets raised and millimeters matter, this is where we see the progressive drop off in return to activity. The margin for error goes down.

-> It’s critical to focus on millimeters here. When you tear your ACL, the torn knee will have something like 1 to 10 extra millimeters of laxity. Meaning, at most, an extra centimeter. That’s what we’re worried about here!

Think of a car vs a plane vs a rocket.

One day you decide to put a spoiler on your car, or one day you duct tape the headlight on, or you decide to put a ton of cargo in the trunk. Even if the spoiler is angled a few degrees wrong, or if the headlight is still dangling some, or if you can hear the engine working harder, you end up driving fine.

This isn’t true with a plane. You can’t randomly add an attachment or duct tape a wing and be fine. You do have some wiggle room with cargo. Say the plane is accidentally heavier than intended, so you burn fuel faster than thought. Perhaps the worst case is you land somewhere and refuel, then finish the journey. Not a huge deal at the end of the day.

Make a rocket heavier than you thought? It doesn’t get to space and comes crashing to earth in a fireball.

Anybody can drive a car; you need specialized training to drive a plane; software drives a rocket. We progressively trust humans less. Human error is increasingly less tolerated.

A car is slower than a plane is slower than a rocket. As speed goes up, as the intensity on the structures go up, the margin for error goes down.

As the speed and intensity of activity a person is trying to get back to goes up, the margin for error goes down. Having a knee that is 90% as strong or stable as it was won’t matter for many, many activities. Even playing basketball by yourself, or your rec league where you’re never moving too fast because your 40 and most of the people playing are overweight, you could be fine. You go back trying to play division I though? 10% is an enormous margin to overcome. You being a measly 3% better than your peers may have been why you got to where you were to begin with.

This is why exercise is so crucial. We want to decrease the margins as much as possible. We understand the new ACL will never be the same as the old one, but we may be able to get it, along with help from the rest of the leg, to be as good. For instance, if before you tore your ACL you never did any strength training, but afterwards you take it seriously, you could very well come back as good or better to your chosen activity, because the 50% stronger you are makes up for the 50% less stable your new ACL is.

Timelines part two- knowing your shit

As a patient, you’re practically hopeless when it comes to knowing what this process entails. The healthcare system doesn’t do a good job of letting people know aspects like the above, and this is not knowledge easily learned by an outsider. Even an insider and it’s going to take some serious dedication.

Furthermore, for everyday people, the healthcare system is not very good at helping this recovery. Overwhelmingly people start physical therapy 2-4 weeks post surgery, when they should be starting the day of surgery. Yes, the day you wake up.

Ideally, you start the day of injury. So by the day of surgery, you’re already ahead of the game. You already know what to do when you wake up. You’ve already been working on preventing quadricep atrophy.

Ideally you know (and have access to) a pool will be very helpful as before you jog outside, you can jog in the pool. You know it’s helpful to do your running after the 8-12 week mark, since your graft has been set and the risk of stretching it with an intense activity goes down. You know at this point it’s helpful to say-

Jog / run in pool backwards ->

Jog / run on land backwards ->

Jog / run in pool forwards ->

Jog / run on land forwards ->

Jog / run in pool sideways ->

Jog / run on land sideways ->

Jog / run in pool with stopping ->

Jog / run on land with stopping ->

Jog / run in pool in all directions with twisting ->

Jog / run on land in all directions with twisting

Because that way you’re always progressively leading into the next activity. You don’t randomly try to go running one day, swell your knee up, and throw up your hands “My knee sucks.” No, your physical therapy and exercise program suck.

It’s rare physical therapists do anything like this. They have you come in, ride the bike, do a few stretches (which often hurt when they shouldn’t), sit on a leg press, do some form of leg curls, do some clamshells, ice and stim, then one day try to run as tolerated.

Most physical therapy offices are maybe 1500 square feet. There isn’t any room to run! (No, a treadmill isn’t sufficient longterm.) I’ve seen countless physical therapy programs. I have not seen one single program involving progressively getting into running as part of it. Just because you can’t have someone do it in your office in front of you doesn’t mean you shouldn’t program it in. Otherwise the person is lost.

Because most insurance doesn’t pay for the amount of therapy for the amount of time people need. Where they’re going to need guidance for what to do on their own anyways.

It’s a very, very tough spot to be in as a patient. We count on, expect, and pay healthcare workers to know their stuff. To guide us. But healthcare is like every other industry. You have your A players, then you have everybody else. We don’t all get access, or even know how to get access, to the A players.

This is the other major factor for so many not making it all the way back. Couple the extensive timeline with not truly getting the physical preparation one needs, and you end up with complications which should have never happened, atrophied quadriceps which should have barely gotten smaller to begin with, trying to regain a range of motion in month three which you should have regained the day of surgery, all leading to frustration, anxiety, depression, sadness.

One of the contentious topics in the “biggest mistakes” ACL post was me saying it was normal to experience all these emotions. It’s normal but not necessary. Normal because the physical end doesn’t get taken care of, so the psychological end takes a toll.

Psychology, sort of

Mentally this is a very hard time for people. Thoughts of “Will I ever be the same again?” can be quite anxiety producing. Particularly in the beginning when all you want is to be able to walk again.

Then as you move along,

  • “Did I do something to screw up the surgery?”
  • “Did my surgeon mess up?”
  • “Am I doing the right physical therapy?”
  • “It hurts to do this, but the physical therapist says I should push through it, should I?” <- NO.

Realizing how little control you have in what’s going on is nerve-wracking, and a great way to produce stress in any situation. None of which is helpful for healing.

That said, just in the questions above, if you know your shit, or have people around you who you know are at the top of the game, all those questions get answered immediately, as does your anxiety.

Charlie Francis is the best sprint coach of all-time. Perhaps the best sport oriented coach of all-time. He loathed sending underperforming athletes to sport psychologists. The way he approached his athletes was if they weren’t ready mentally, that means they weren’t ready physically, which was on him. Not them. Him.

His athletes didn’t have anxiety of not knowing how fast they could run before a race. Charlie had his athletes practice at top speed. Race day was another practice day. Nothing new was about to happen. It was routine.

-> In my experience, if a client has something persistently psychologically detrimentally going on, it’s more to do with the rest of their life, where a professional can be helpful.

On any given day someone was sore, they would immediately be taken to stretch or have a massage or warm up some more to get them not sore, or be moved to a different part of the workout where the soreness wasn’t a factor. You don’t produce stress and anxiety by having an athlete worry “Am I messing something up right now?” You avoid that emotion. Not by telling them to suck it up or be mentally tough. But by putting them in a position to succeed.

Physical preparation largely dictates mental preparation.

Peyton Manning struggled in the playoffs when the weather was cold. When in Indy, he played half his season in a dome. For four of the away games, he played in Houston, Jacksonville and Tennessee. Going from that to all of sudden New York or New England in January isn’t ideal. It’s doubtful a guy who got hit for a living had some weakness for cold weather. His body just didn’t have the experience of dealing with it. It’s like why Lebron struggles with the heat.

When Steph Curry had to miss time in the playoffs a couple years ago, once he felt healthy the Warriors didn’t throw him into a game. They instead brought him into a 3 on 3, then gave him a day to see how he felt. After that, he went into a 5 on 5 simulated game. Still feel good? Ok, now we can go back into a game, at reduced minutes. Curry didn’t think his way back to being healthy. He was physically prepared, making him mentally prepared, to get back to into a game.

Get a surgeon you feel comfortable with or don’t have the surgery. Find, BEFORE SURGERY, a physical therapist or a plan you’re comfortable with, or don’t get the surgery yet. Find out exactly what you should expect at various timelines.

  • “What graft are you using and why?”
  • “How long should I not go to work?”
  • “What exercises should I be doing after waking up?” <- Doing nothing is not an option.
  • “Roughly when should I expect to be running again? How will we progress into that?”
  • “How many ACL surgeries do you do per year?”
  • Helpful, though not necessary -> “Have you had ACL surgery? What level of activity did you get back to?”

You don’t need to have everything mapped out for the entire process -you always want some leeway to adapt- but you should have a good idea of what’s coming before it comes. Nothing should feel random. Leave the suspense for TV shows or movies.


Want to know what to expect the first month of recovery? Check out The most important phase of ACL rehab.



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