Something ACL patients, really any knee surgery patient, struggles with the most is regaining full knee extension. Out of surgery, many lay their legs straight, and one knee looks like this, if not worse.
Next thing you know they’re walking like this,
We’re talking not only the ability to straighten your leg, but the ability to hyperextend your knee. If straight is zero degrees, then hyperextension would be another 7 degrees, give or take. Rather than your ankle and knee being lined up, your knee can go a little behind your ankle.
(You do not want to work on your knee range of motion while standing though!)
I’ve had the amazing fortune of spraining my knee, having reconstructive ACL surgery, and having a partial meniscectomy. I have, for the most part, seen the gamut of knee injuries, personally and professionally.
Excluding extenuating circumstances, like complication from a knee replacement, by far the hardest time to regain knee extension range of motion is after ACL surgery. It was something I needed to work on every hour of every day (not hyperbole), for the first 6 weeks after surgery. It took until about the three month mark where I didn’t need to worry about it multiple times a day. By worry about it, I mean if it wasn’t done at these time intervals, I’d lose the range of motion, and it could take many minutes of stretching to regain it.
Many experience the same thing. Although, some regain full range of motion like it’s nothing. Beyond the readily apparent, like pain, inflammation, why is this so hard? Why do some have no problem at all? Is there anything unique to ACL surgery making it tougher than other injuries?
–
What does the anterior cruciate ligament do again?
The ACL goes from the back of the femur to the front of the tibia.
Credit: https://www.studyblue.com/notes/note/n/knee-tissue-and-nervous-system/deck/1316154
The ACL subsequently prevents the tibia from going in front of the femur. It pulls the tibia back to the femur.
To test if an ACL is torn, you’ll see an orthopedist gauge how far they can pull the tibia forward relative to the femur.
Credit: http://www.orthopaedicsone.com/download/attachments/4554895/lachman+7.JPG
If it’s really lax, there’s probably a tear. (Why you don’t want a non-orthopedist testing your ACL.)
–
What happens to the ACL during knee flexion and extension?
I am simplifying this some. If you want more details, such as breaking the ACL into anteromedial and posterolateral bundles, check the Wheeles discussion. That level of specificity isn’t needed here.
As the knee bends, the ACL is tautened as the tibia moves forward relative to the femur / the femur moves backward relative to the tibia.
This is one reason there are often, though not always, flexion range of motion restrictions immediately after ACL reconstruction. You go bending the knee too much, you might stretch out the graft.
When coming into knee extension, particularly some hyperextension, we can again see the femur moving back relative to the tibia. Really watch the last bit of this animation:
GIFs made from this video.
The more obvious: When you get a new ACL, the graft is tautened when put in your body. Your range of motion can be based on how tight the graft is. A really tight graft and it may be harder to work on flexion and or extension range of motion
The less obvious: I recently went in into an operating room and watched an ACL reconstruction. There are a couple moments where you knew the surgeon was tightening the graft. He would let out a huge grunt, like he was lifting heavy weights. As he jokingly said, “When you grunt, that’s how you know it’s tight!” The idea is this thing is really, really put in there.
-> In dogs, a veterinarian surgeon has told me they’ve given up on reconstructing the ACL. Due to the dog’s anatomy, their physical strength, and how hard it is to manage a dog post-op, they too often rip or stretch the graft. This another reason in humans we don’t (or at least shouldn’t!) go running like crazy a month post-op, or only do things based on pain. We need to give the graft (typically a tendon) time to set in the bones, as well as time to transform (into a ligament).
Not only that, but during the final phase of surgically inserting and tightening the graft, the tibia is pushed backwards relative to the femur.
- Pull the tibia forward relative to the femur => ACL tautened
- Push the tibia back relative to the femur => ACL slackened
Meaning the graft is tautened in a position the ACL is usually slackened. Tighten graft -> Push tibia back relative to femur to slacken graft -> Then tighten graft again. The new ACL is put in tighter than a normal ACL would be.
This was being done by two grown men at the same time. One guy was working with the femur and tibia, the other guy was working with the tibia some, but also finishing up on the graft.
-> I got more of an understanding why orthopedic surgeons plan to retire by 63 years old. It’s a physical job.
Two men putting the leg into position, specialized materials apparently stronger than anything in the body, with one guy using damn near all the strength he has. That’s how this thing was put into place. This is thing is put in tightly.
Beyond wanting the graft secure, the idea here is despite all this, over time, the graft will likely still loosen up some. By placing the graft in a position where the ACL is actually a bit shortened, as it loosens up some, it will then be in a normal resting position. It’s a fail-safe; attention to detail at the highest level.
But going back to our knee extension range of motion, what do we know happens as we approach some hyperextension?
The ACL stretches a little bit. Our knee has just been manipulated with two men using super strong materials to hold their manipulation, which prevent this anterior tibial translation. No wonder it’s hard to get knee extension range of motion back!
–
Fear not?
We often worry about bending the knee too much too soon, but we don’t worry about straightening it too much, too soon.
By regaining knee hyperextension range of motion, we’re talking only 7 degrees or so, relative to neutral. The graft is placed in a position where it’s expected it can loosen up to this point. Furthermore, the force on the ACL is quite small in hyperextension. Maybe 10% of what the ACL can handle. (Initially, something like a quadrupled hamstring graft is stronger than a standard ACL. So they often have an even better ratio in this regard.)
In knee flexion, we’re talking up to 120 degrees, relative to neutral, and the ACL is the primary restraint to anterior translation of the tibia from 30 to 90 degrees. Accounting for 80% of the work. Furthermore, anterior tibial translation -stretching the ACL- is greatest between 20 and 45 degrees of knee flexion.
There is a significant discrepancy in ACL stress, and range of motion, between going to full extension and full flexion. This is one reason some will end up locked in a brace for 10-14 days, before being allowed to bend the knee. The decision is to eliminate all bending to minimize ACL stress. But that bit of stress in full extension? Not worth worrying about, and regaining full extension is much more important than full flexion. The cost / benefit of stretching the graft versus regaining full extension is clearly in favor of full extension, while the cost / benefit of stretching the graft versus regaining full flexion is in favor of being careful with knee flexion. Particularly active flexion, where passive isn’t as much of a concern.
-> For 8-12 weeks is a good ballpark. Patellar graft is believed to be set by ~8 weeks; hamstring graft by ~12 weeks.
–> Takes ~18 months for them to transform to a ligament though!
-> If you’ve had a meniscal repair, common with ACL pathology, you’ll want to be even more careful with knee flexion, as flexion mobilizes the meniscus.
That said, this doesn’t happen to everyone. Even the surgeon I watched, when I asked him about locking people straight, he said it was mainly to let the leg calm down more than anything else. It seems some feel good enough about the graft, or the materials they’re using, they don’t worry about range of motion after surgery. (Passive range of motion. Everyone worries about active, and how intense the active is.) Although, you’re unlikely to see anyone allowed to bend past 90 degrees for at least a couple weeks. The swelling probably won’t let you anyways.
I’m not sure if every surgical team does things this way, where they place the graft in a position of being extra taut. I unfortunately didn’t think to ask this question at the time, although I’m not sure they would have known. My impression is this isn’t always done, and this is why some people may not have as hard of a time regaining range of motion immediately post-op. However, their graft may not be as well set as someone else. It’s quite possible having trouble regaining knee hyperextension after ACL surgery is a sign the surgical team did a good job, and that if you regain things too easily, things may not have been as well set as they could have been.
With the body, it remains whenever you gain something, you lose something.
–
For a plan dedicated to making the initial ACL recovery as smooth as possible, go here.
For a plan focusing solely on being able to straighten your knee again, go here.
getontheline
December 18, 2015
I didn’t really have issues with extension the first few weeks after surgery. My knee would bend but mostly because of the swelling but once that went down after a few days, I never really had to work on the extension to the extent you mentioned in the post. Part of the reason was I stayed locked in the brace for a good 3 weeks thinking that this would help with the extension (especially when I sleep).
reddyb
December 20, 2015
Everyone is different. Some regain extension without ever working on it, ala they never lost it post-op. One person I recently worked with had no issues regaining hyperextension. However, 4 months post-op, they scheduled another surgery. It may, sometimes, be a negative sign if things are regained too easily. This person never even thought to work on their extension yet had no issues with it. That’s almost too easy!
I was locked in a brace for about two weeks, and (hyper)extension was still incredibly hard for me to maintain.
The distinction between being straight and hyperextension is crucial. Many never even assess their ability to hyperextend. In the photo I show where the legs are laid straight, but one knee is bent, even if both knees were straight, that wouldn’t be hyperextension for most. The feet need to be elevated a little in order to assess hyperextension. It’s just not common to even think about knee hyperextension throughout life, especially compared to bending the knee. Beyond inadequate physical therapy, what I’ve seen with clients is it doesn’t cross most people’s mind to even consider it post-op.
Salah
January 28, 2016
After acl reconstruction and meniscus repair surgery that was done 6 month ago I had to do another sugery one month ago because i did not get full extension. My doctor told me that i had cyclops lysion that is why i could not fully extend. Aftr the surgery my knee is better and very close to full extension. My question is my normal knee has 4 to 5 degress of hyperextension. Will my operated knee get this hyper extension like the normal one ? How can i achieve this ? Is it must to have both knee in same hyperextension ?
reddyb
January 29, 2016
Hey Salah,
In terms of what to do for regaining knee extension, there is a manual here solely about this: http://b-reddy.org/2015/09/03/help-i-cant-straighten-my-knee/
If everything has been cleared out of the way, then I’m unaware of anything which would prevent you from equalizing things. But I will say cyclops lesions, and surgical recovery from one, is not something I’m as familiar with. There is a commenter, Jonathan, on the “Biggest mistakes” ACL post ( http://b-reddy.org/2013/10/23/the-biggest-mistakes-acl-patients-make/ ) who may have more info for you on this.
Overall, getting things to be symmetrical between knees is definitely the goal.
Annette Ledesma
May 10, 2016
I am 1 year post op. I have regained my flexion. I still can’t quite get the hyper extension in my knee. I hear that in most cases hyper extension is unattainable. Is this true? Are there any exercise suggestions that will help me attain some hyper extension?
reddyb
May 10, 2016
That’s not true.
Have a manual dedicated to this: https://b-reddy.org/2015/09/03/help-i-cant-straighten-my-knee/
Homer
July 1, 2016
I am 2 years post op acl reconstructed and never regained full extension. Is it gone forever?
reddyb
July 4, 2016
Hey Homer,
Would read this: https://b-reddy.org/2015/09/03/why-you-dont-want-to-wait-to-regain-knee-extension-range-of-motion/
Rob
July 31, 2016
Great site reddyb. How strong, compared to native acl, does hamstring graft end up being once it has become a ligament after 18 months? Is it likely even with acl recon that in older age knee replacement is likely?
reddyb
August 2, 2016
Good question!
I’m not sure there is an answer out there on this, or even could be one. To do this you’d have to take knees that have been reconstructed, then ~18 months later assess at what load do they tear / deform enough as to be torn. Due to the ethics, that study isn’t going to happen.
Beyond that, you’re faced with animal and in vitro studies, which are going to be very different than humans and in vivo. (Probably more info than you ever wanted on differences between quadruped ACLs and humans: https://b-reddy.org/2016/04/06/is-there-about-to-be-a-revolution-in-acl-surgery/ )
Off the top of my head, virtually all grafts are *stronger* than the native ACL in vitro. That is, before placed in the body. Histologically, the native ACL doesn’t ever seem to reappear, despite a good deal of “ligamentization.” If you want to get into the weeds some: [redacted broken link]
Now whether that means strength will never be the same, I don’t know. The graft could very well be stronger / as strong, but stronger doesn’t automatically mean better. Another element here is the proprioceptive ability of the graft. For instance, how well does it respond to a stretch sensation. Nerve oriented stuff like this is notorious for being stubborn when it comes to coming back “good as new.” I wouldn’t be surprised if something like pure strength was more than good enough, but proprioception tended to lag. (I believe there is research out there on this, but I haven’t gotten into it (yet).)
Never mind ACL reconstruction, ACL injury makes arthritis more likely. That’s going to impact the likelihood of knee replacement down the line. That said, if one takes care of things after injury / surgery, knee replacement can definitely be avoided.
-Brian
Rob
August 6, 2016
Thank you Brian for such a comprehensive answer and taking time to answer mine and everyone’s questions. It honestly is re-assuring just have an answer even if of course the real aspect, as you have touched on, to deal with is acceptance no matter what treatment the knee is never the same.
reddyb
August 7, 2016
You’re welcome, and thanks for the nice words Rob.
Remember while the knee is forever different, many can still get back to a great deal of activities. How these things get managed is part of what will likely be different for most, compared to pre injury.
Rob
August 24, 2016
I also meant to ask how your knee feels now, comparative to the uninsured knee? Over time is it feeling more normal or are you still constantly aware of the deficiency?
reddyb
August 26, 2016
Hey Rob,
It can tak 18-24 months for someone to feel their most normal. Personally, I kept feeling more and more normal until the 18 month mark.
Intend to write more about this and show some examples in the future, but my knee has no deficiencies *functionally*. That does not mean it always feel like my other side though. I get sensations on the operated side I don’t get on the non. (In the cut hamstring for instance.) I’m also more cautious about managing the loading of my legs than I would be otherwise.
Another example is I tore my ACL from playing flag football on a crappy grass field. I play tennis because I can dictate what happens to my legs, and I’ll go for a run on a grass field because I can watch every step I take, but I’m not sure I’ll ever go do something like play soccer or flag football on one again, where I can’t be in that type of control or that mindful. Many fields rec athletes use are not well maintained. Can my knee go out there on one? Yes. Are the chances the field will be that bad again and I’ll take the perfect step in that location to tear an ACL again really small? Yes. Will I go out there though? No.
So in my case, you might not say “aware of the deficiency.” Instead you might say “aware of the history.”
Rob
September 9, 2016
Thanks Brian. I’m tired of my leg feeling the way it does. When I get my operation out the way and recovery I just hope it feels similar. I appreciate the lack of nervous tissues and other damage will mean it feels different but it will just be nice to walk and feel like it used.
Karthikeyan Krishnamoorthy
September 23, 2016
I feel like crying. Meniscus Tear and ACL Reconstruction done in one year back. Still unable to walk properly. Walking with bent knee. Operated knee is still looks bigger or swollen than the normal knee. Once i get up after sitting, stiffness is there. Do not know what to do?
Sometimes i feel, my doctor cheated me. Before going to surgery, he told me only meniscus tear is there after seeing SCAN report. however, during mid operation said ACL Tear is there it has to be reconstructed.. Without any option, i said yes in the operation table.
Further, the doctor told, no physiotherapy is required. it will be ok by 6 months. However, on my other friends insistence, again i went to the doctor and said i am ready to go for physio , he said it is not required. that is old method. Nowadays it is not required.
So, i believed and did went for a physio at all. He only told me to do some cycling and knee stretching.
But now, i am left with a leg which is not straight, stiff knee, and i am not able to walk straight, god knows what will happen in my old age. Feel like crying. So depressed and frusstrated.
Is there any hope for me to get back to normal. Can i consult a separate doctor. can i go for again a surgery.
Can anybody give me suggestions. Suggest a good ortho suregeon either in baroda or madurai or trichy doctor to go for once again a surgery or atleast consult for rectification.
reddyb
September 25, 2016
Hey Karthikeyan,
I’m sorry to hear about your tough experience.
If you don’t have full extension, that’s the first step. I discuss some of the timeline issues, such as someone who has gone a long time without having full extension, here: https://b-reddy.org/2015/09/03/why-you-dont-want-to-wait-to-regain-knee-extension-range-of-motion/
And there is a manual aimed at regaining extension here: https://b-reddy.org/2015/09/03/help-i-cant-straighten-my-knee/
Michelle Tshimanga
September 25, 2016
I’m on the verge of tears right now. I’m buying your book. My case is… ugh. I don’t even have the words for it. I feel like I made loads of mistakes along the way. I was 13 when I tore my ACL, partially tore my MCL and damaged my meniscus. Because I was so young, my mother opted that I wait for surgey. I played varsity basketball and field hockey with this injury for 5 years. I wore a huge knee brace but I was eventually able to fully extend AND flex my knee. Mind you, if I stepped the wrong way my knee was incredibly unstable but I had full range of motion. I ended up getting surgery, went to physio briefly and left it at that. I wasn’t able to extend my knee so I went back to my surgeon and got an arthroscopy (?) done. Still couldn’t fully extend my leg. My surgeon then sold me a knee stretching brace for $1500. Still have a bent leg. I’m realizing now what effect this has on my back, my posture, my walking and of course the atrophy of my injured leg. I’ve been limping and walking with an awkward gait for 6 years. I fear I’ll be like this for the rest of my life. I deeply regret getting surgery and I hope your book can help some. I’m not sure if you read this, but thanks if you did.
P.S. – The first picture you posted looks exactly like my knee. 6 years man…. 😢
reddyb
September 27, 2016
I’m sorry to hear about your situation Michelle. Hopefully the book can help you regain that extension back. I’ve seen multiple people who after a while were able to get a good deal back. It does require some serious diligence, but it can be done.
There is some info on wrapping here, which can help with swelling: https://b-reddy.org/2012/07/12/how-to-wrap-knee-pain-a-knee-injury/
Sujay Roy
September 26, 2016
Hey reddyb
I had an ACL reconstruction with lateral meniscus repair a month ago. The problem i am facing is while lying down straight on my bed with both legs straight, the operated leg remains flexed a bit or the back of the knee of operated leg is elavated from the bed surface. It is same as the pic you attached in the very first segment of this page. So is it a thing to worry or is it normal.?
reddyb
September 28, 2016
Hey Sujay,
That is something to worry about. By a month out, you want to have full extension. Something I’d be very diligently working on. The longer you go without it, the more likely you are to never get it back.
AMIR
September 30, 2016
Hey Reddyb,
I have the same case as Sujay Roy. I had a complete ACL Tear at the Femoral Attachment as well as a Bucket-Handle Tear of the Medial Meniscus with Fragment Flipped into the Intercondylar Notch. Sep 1st, 2016 i had a surgery when i got my ACL reconstructed using graft from my Hamstring as well as a removal of the Meniscus at the affected area. I’ve been doing lots of exercises at home as well as lots of Physiotherapy sessions. I’m doing good in Flexion, i can reach 92 Deg and the Muscles are starting to work however i feel i’m doing really bad in the extension, i can reach only 18 Deg extension. My Leg is inclined like the first picture in this page. What do you think could be the reason of such 18 Deg off ? Why cannot i reach the 0 Deg ? Is this because of the Meniscus removal ? Is it normal to take that long time ?
Please advise.
Thanks in advance,
Amir
reddyb
October 2, 2016
1) Rehab has not been proper. “Lots of exercises” unfortunately doesn’t mean anything in this context. How you do it, what you do, etc. is what matters.
2) Something is in the way, in the knee e.g. “cyclops lesion.”
3) It does not need to take longer than 24 hours to regain full knee extension. Though too many wait longer than this to get it back.
Luke
January 15, 2017
5 months post op – ACL replacement – repair bucket handle tear meniscus – still can’t fully extended without sitting down and stretching the knee cap – The doc said recovery would be 9 months but it’s hard to walk correctly when you have trouble with extension and/or no hyperextension… I have done everything they have asked and more and i have been in the pool the last 2 months (3 to 4 x per week for 45 min) walking, jogging, leg kicks, etc.
Should i get a second opinon? or will the full extension/hyperextension evenually come? PT has said for a couple of months that my patella is very tight and this keeps the bones from gliding smothly (you have to get that patella moving freely again). My leg muscles (quads) are still still. Any help?
reddyb
January 17, 2017
Hey Luke,
While you may have done everything asked of you, the pool, walking, jogging, leg kicks, are not likely to improve knee extension range of motion. Furthermore, particularly in the beginning of rehab, knee extension should be worked on *every day*. 3 to 4x per week is not ideal. Some need to work on only their knee extension range of motion for 45 minutes per day! Never mind all the other work.
The full extension will not come over time unless it is specifically worked on. It is something which can, and should, be achieved the day of surgery. (Seriously.) It’s not a time / healing dependent issue, at least not initially.
Not trying to pick on you, this could very well be the fault of those you’re in the care of. If you pick up the Regaining Knee Extension manual you may see much more detail and necessary work than what you’ve been exposed to so far.
The number one reason people don’t have full knee extension post-op is not doing what’s necessary to get it. (Why that happens again could be someone besides the patient’s fault.) Besides that, surgical considerations can come into play.
Regarding your therapist, it could very well be time to get a second opinion. Always hard to know these things as I don’t specifically know what they’ve asked of you. If your description is all there’s been though, then a second opinion is probably the way to go. Same would go for the surgeon.
Luke
January 17, 2017
Thank you. So no matter what I do now from your experiences, I won’t be able to achieve full knee extension and /or hyperextension? I guess I need to get a 2nd opinion from another orthopedic physician. This is quite disappointing and I assumed and trusted that my PT group knew what they were doing. I have your manual by the way
Thanks
Luke
reddyb
January 20, 2017
You won’t be able to achieve it without dedicatedly working on it. The longer you go without it though, the harder and less likely it is to get all of it back.
I *have* seen people who went years without full extension after a knee surgery, and did get significant improvement once properly working on it.
If you have the knee extension manual you can see the amount of time and effort it takes each day. It can be rather tedious how stubborn the knee can be.
That said, each set of working on it you should see some improvement compared to how the knee started. For example, your knee can only extend to 0 degrees. You do a set of knee extension stretching, after a few minutes you should have a little more range of motion. You might lose that range of motion within a couple hours and need to work on it again, but there should be some improvement. (Getting it to stick without needing to work on it all the time is what can take weeks / months.)
If there is no improvement when you work on it though, that’s where I’d be pressing the surgeon. There are situations where something internally can be blocking the knee (cyclops lesion).