The first goal of anyone who has ACL surgery is to get their range of motion back. ACLers almost always wake up feeling tighter than they were when they went into surgery. This is completely normal, as surgery (even arthroscopic surgery) is a trauma to your knee that will lead to swelling, tightness, discomfort & range of motion loss, especially in the immediate post-op phase. After an ACL surgery, patients will often have difficulty bending their knee (flexion) as well as straightening their knee (extension). The goal of getting the motion back in both of these directions dominates the early guidelines you will receive from your surgeon, PA and physical therapist. Furthermore, the first thought of most patients when they wake up from ACL surgery is : “when will I be able to fully bend my knee again?” Let’s dive into this blog to find out.

 

When can I start to work on my range of motion after surgery?

Day 0. That is right, the day you have surgery you should be able to start gently working on your range of motion (ROM). Now, you must follow your surgical precautions and this can often vary, however there is really no additional procedure that can be done that the evidence supports a prohibition on early, gentle, passive range of motion in a limited range. In most cases, when ACLers are left to believe they need to stay locked in a brace until their first surgical follow-up or their first PT appointment, it is because not enough time has been spent on pre and post-op education and the guidelines have not been made clear.

For you as the ACLer that means, ask your surgeon ahead of time: “Can I start gentle passive range of motion right after surgery just to get my knee moving?”

Re-establishing normal flexion and extension after ACL surgery is a primary goal, a huge milestone, and a constant battle during this rehab. It is something that will take daily work and attention for at least 6 months and most likely closer to a year. Despite this being a primary goal of everyone involved, many ACLers & healthcare professionals misunderstand the best ways to achieve, and maintain range of motion throughout this rehab. Let’s get into that next.

 

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Sometimes showing the surgeon that you are a conscientious patient who can be trusted not to crank on your knee right away will enable them to give you a bit clearer guidelines. If this seems like quite a bit of hassle for starting to work on your range of motion just a few days earlier, I can assure you it’s worth it. In that early post-op phase, the saying “motion is lotion” reigns supreme. The earlier you can get your knee moving, the better you will feel. While it may be uncomfortable at first, early gentle passive motion will increase blood flow to the area, help start to reduce swelling by assisting venous return (the return of fluid to your heart through your veins), and start to desensitize the surgical knee.

 

 

To be clear: your knee will not move very much, and it doesn’t have to. However, by supporting your knee with your nonsurgical leg, letting your surgical leg relax, and gently working your knee back and forth in a limited but gradually increasing range will help get everything moving in the right direction.

 

 

Getting your Flexion Back

We’ve established that the earlier you can start working on your range of motion (while obeying your surgeon’s precautions), the better, but when it comes to getting your flexion back – how do you actually do it? If you are an ACLer, this next sentence is a key that you should remind yourself of constantly when trying to gain flexion:

“You will never be able to actively gain range of motion you don’t already have passively.”

 

What does that mean?

It means that when you are using your muscles to actively bend your knee to improve your knee flexion, you are making your life immeasurably harder. Passive range of motion means using an external force (aside from the muscles of your surgical leg) to bend your knee. There are a variety of ways to do this, which we will go through, but the key is that the muscles of your surgical leg are completely relaxed as you use the force of something else to help bend your knee.

In the early post-op phase, the best way to do this is through Seated Supported Knee flexion. In this exercise, you are using the external force of gravity to push your knee into deeper flexion, while you use the muscles of your nonsurgical leg to support that surgical leg and control that force of gravity, thus making it more comfortable.

We’ve found this to be the best option for working your flexion in the immediate post-op phase while your flexion is less than 90 degrees. Another option in a similar vein is a Wall Slide in which gravity is once again pushing your knee into deeper flexion, but the support of the wall is slowing down that descent. Personally, I’ve found more success with the seated supported knee flexion, but some people prefer the wall slide. Either way, the key is that you are relaxing the muscles of the surgical leg and slowly working into more flexion.

 

 

Once you’ve achieved 90 degrees of flexion or close to it, Heel Slides utilizing a strap to gently pull your knee into flexion are typically the best option. In this case, the external force comes from your arms pulling on the strap to bend your knee, and you must do your best to relax your surgical leg as best as possible.

 

As you continue to gain flexion and get further out from surgery, closed chain flexion most often in the form of a child’s pose exercise, becomes a great option for helping get your heel to your butt and allow you to kneel the way you would have before surgery. Most ACLers do not need to start working this earlier than 3 months post-op, and you should have at least 120 degrees of flexion to begin working on flexion in this closed-chain fashion. The reason is that the addition of weight-bearing on that knee in this type of loaded flexion presents an additional hurdle that is difficult to overcome if you aren’t already close to getting that end-range flexion and if you haven’t fully established a quiet knee.

 

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In all of these different exercises, there a few keys to make sure you are successful:

1. You should never put yourself in agony trying to bend your knee; the goal is to work to the point of mild to moderate discomfort and slowly increase how far you can get.
2. While you can work your flexion too aggressively (leading your muscles to tighten up in a painful response and actually lose ROM), you CAN’T work it too often; the more often you work your flexion, the better. Early on, working your flexion for 5 minutes every hour is a great rule of thumb.
3. Slow, steady, consistent gains: try to get 1 degree of range of motion every set and then let those gains compound over many sets.

Getting (& Keeping) your Extension

While gaining flexion is all about consistency and working that ROM early and often, getting your extension back is a little bit different.

The key with extension is something called “low load, long duration stretching.” This means that from the minute you wake up from surgery, your resting position should be with your heel propped up, nothing behind your knee, letting gravity push your knee into full extension.

 

READ: THE IMPORTANCE OF KNEE EXTENSION FOR QUAD STRENGTH

 

I can’t emphasize this enough: whenever you are sitting, for as long as you can tolerate – get that heel propped up and let gravity slowly push you into extension. A good phrase to remember is “Tolerate prolonged discomfort now to avoid pain later”.

Propping your knee up early post-op will not be comfortable. The muscles behind your knee that have co-contracted in response to the trauma of surgery will be angry, tolerate it anyway. Take breaks as often as you need but set the goal of trying to expand to heel propping as long as you can early and often instead of trying to gain it all back at once later on with your PT pushing on your knee.

For the first 4-6 weeks, this heel propping should suffice while your knee is still healing from surgery. However, as you get further from the surgery, if you still have not established full hyperextension matching the other side, you will want to progress to something called a Backpack Hang. By adding weights to the backpack, you can slowly increase the tension on your knee, increasing the amount of extension you can achieve. The goal is to work your way up to 10lbs in the backpack for 10 minutes, twice a day.

 

Even once you’ve started backpack hangs the heel propping should still be your resting position. Again, it is better for your knee to tolerate prolonged discomfort than short bursts of intense pain, which will leave you tightening up later on.

While flexion can take many months to achieve fully, many ACLers who achieve full heel to butt flexion don’t do so for 6-8 months; extension is crucial to establish as early as possible. Achieving full hyperextension early on decreases the opportunity for scar tissue that would limit that extension, such as a cyclops lesion, to develop. When it comes to extension, you must establish it early on, and then the hard part is to make sure you keep it! This is where walking mechanics, strength, and load management come in.

 

The Role of Walking, Strength & Load Management

Many ACLers & PTs fall into the trap of focusing exclusively on range of motion in the early post-op phase, without recognizing the role that strength training and walking mechanics plays in both achieving and keeping your ROM.

One of the primary things that limits your range of motion early on is the co-contraction of muscles around your surgical joint. This co-contraction is your body’s way of trying to protect the joint after the trauma of surgery. Starting to slowly train and activate those muscles will actually help them relax and help you slowly gain range of motion.

To succeed in ACL rehab, you absolutely should start strength training before you’ve achieved full range of motion. The key is to start strength training actively in the range of motion you’ve already achieved passively. This means that you shouldn’t be trying to gain knee flexion by squatting deeper, but you absolutely can and should squat in the range of motion that you already have.

 

READ: HAMSTRING TO QUADRICEP STRENGTH RATIO

 

The other reason strength training early on is critical is because it will allow you to support your bodyweight in normal walking, which will make it easier to gain range of motion as well as to keep it.

If you don’t have the strength to support yourself in normal walking, that impact through your joint will lead to more joint discomfort, swelling, and further co-contraction of those muscles, thus making it harder to gain range of motion.

Furthermore, one of the hardest parts of normal walking is controlling hyperextension under your full bodyweight. If you don’t have the strength to control hyperextension when you walk, all the range of motion work in the world won’t make a difference as you will continue to walk on a bent knee and struggle to keep the extension you’ve achieved with your stretches.

 

2 of the biggest mistakes you can make as an ACLer are:

1) Rushing off crutches before you are ready without real functional criteria

2) Not managing the loads on your knee with both your exercises as well as in daily life. This means monitoring the number of steps you are taking and either using crutches or resting when you reach a point of fatigue that prevents you from walking normally any longer.

Gaining range of motion is about more than just stretching; it requires strength training, load management, and proper walking mechanics throughout the day. Working all of these in parallel is crucial to gaining back your full ROM as smoothly as possible.

 

The Myth of Your PT Getting Your Range of Motion

I want to pause here to harp on a critical misunderstanding that is all too common in ACL rehab today. Many ACLers & PTs alike think that the goal of a PT session is for the PT to manipulate your knee into increasing ranges of motion through manual therapy and passive range of motion. Part of this stems from the utilization of measurements with a goniometer to document progress in their notes and justify continued skilled PT to insurance companies. While there is certainly a place for manual therapy in the early post-op phase as well as tracking and documenting progress, the focus on gaining range of motion during the session is often counterproductive to long-term gains of range of motion.

Your PT should NOT be cranking on your knee to the point of severe pain to increase your ROM. While this may help you achieve a greater ROM on the table and allow for a better number to be documented, you will often respond to this pain by tightening up later and making minimal gains as the weeks add up. The better way to do this, as outlined above, is to utilize all of the time you have available to you and work this range of motion early and often throughout your day, gaining a little bit each time and seeing those small gains compound over time. I can’t emphasize this enough:

 

 You will be the one who gains your range of motion back, not your PT.

 

The recipe for success in gaining range of motion is:

early consistent passive range of motion work

+ proper gait training and mechanics

+ strength training in a limited range of motion

+ managing the loads on your knee to avoid loss of range of motion through overload

= smooth successful achievement of full ROM.

Closing Thoughts:

Re-establishing both flexion and extension range of motion after ACL surgery is are critical early post-op goal. When it comes to flexion range of motion, starting to bend your knee early on after surgery will help those gains start to come more easily. The best way to gain flexion ROM is through gentle, consistent passive exercises often throughout the day. Working this through exercises like seated supported knee flexion and heel slides for 5 minutes every 1-2 hours will allow you to gain your desired flexion range of motion without ever having anyone push you into intense pain.

For extension, getting your knee into hyperextension as early as possible through low-load long long-duration stretching is absolutely foundational to your success in this recovery. This is achieved by making sitting with your heel propped up and your knee unsupported the resting position for a majority of your day, as well as by the addition of backpack hangs as you reach 6-8 weeks post-op.

For both directions of ROM, early strengthening helps to relax your muscles and support you in normal walking. This makes both achieving and maintaining your ROM much easier. To smoothly and successfully gain a range of motion, you need:

•  Daily passive ROM work
• Gait training to establish normal walking mechanics
• Strength training in ranges of motion that you’ve already achieved passively
• Load management to prevent overloading your knee.

 

The key to success in this endeavor is that you take ownership of gaining back your ROM and utilize all of the time you have available during your week rather than relying on the manual treatments of your physical therapy sessions to gain back your range of motion.

 

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References:

1. Brinlee AW, Dickenson SB, Hunter-Giordano A, Snyder-Mackler L. ACL Reconstruction Rehabilitation: Clinical Data, Biologic Healing, and Criterion-Based Milestones to Inform a Return-to-Sport Guideline. Sports Health. 2022;14(5):770-779. doi:10.1177/1941738
2. Adams D, Logerstedt DS, Hunter-Giordano A, Axe MJ, Snyder-Mackler L. Current concepts for anterior cruciate ligament reconstruction: a criterion-based rehabilitation progression. J Orthop Sports Phys Ther. 2012;42(7):601-614. doi:10.2519/jospt.2012.3871
3. Failla MJ, Arundale AJ, Logerstedt DS, Snyder-Mackler L. Controversies in knee rehabilitation: anterior cruciate ligament injury. Clin Sports Med. 2015;34(2):301-312. doi:10.1016/j.csm.2014.12.008
4. Lynch AD, Logerstedt DS, Grindem H, et al. Consensus criteria for defining ‘successful outcome’ after ACL injury and reconstruction: a Delaware-Oslo ACL cohort investigation. Br J Sports Med. 2015;49(5):335-342. doi:10.1136/bjsports-2013-092299
5. Grindem H, Snyder-Mackler L, Moksnes H, et al Simple decision rules can reduce reinjury risk by 84% after ACL       reconstruction: the Delaware-Oslo ACL cohort study British Journal of Sports Medicine 2016;50:804-808.

About the Author

Tommy Mandala

[P]rehab Writer & Content Creator

Tommy Mandala is a Doctor of Physical Therapy, Board Certified Clinical Specialist in Sports & Orthopedics, and Certified Strength and Conditioning Specialist in New York City. He is the founder of ALL IN ACL, a digital coaching platform dedicated exclusively to helping ACLers return to the life they had before their injury with full confidence in their knee. Prior to that, he worked in the sports clinic at Hospital for Special Surgery, the #1 Orthopedic Hospital in the country. While there, he had the opportunity to hone his skills as an ACL specialist working closely with world-renowned surgeons and evaluating patients from all over the world. He completed his sports residency training at the University of Delaware where he had opportunities to work with many of their Division I sports teams as well as the Philadelphia 76’ers NBA G-league affiliate, the Delaware Blue Coats. He also trained at Champion Sports Medicine in Birmingham, Alabama where he had the opportunity to learn from researchers in the American Sports Medicine Institute. Currently, Tommy works exclusively with ACLers through his digital coaching model. While many of these clients are athletes, Tommy works with ACLers of all different abilities helping them to build the strength they need to overcome this unique injury. One of his favorite aspects of his job is taking active clients who have never been a “gym person” before and showing them the amazing things that happen when they learn to strength train.

Disclaimer – The content here is designed for information & education purposes only and is not intended for medical advice.