Avoiding Post-Op ACL Rehab Problems: The Keys to Recovery

Whether you’re someone who recently tore their Anterior Cruciate Ligament (ACL) or someone who’s currently working through the recovery process, navigating ACL rehab can be scary, especially if you’re looking to return to higher-level sports or activities. Working with a physical therapist whom you trust is especially important when developing a plan that maximizes strength, mobility and function. On top of that, here are 3 important things to also consider during your ACL rehab to avoid potential roadblocks and ultimately get you back to everything you want to be doing whether that be running, playing sports, or just generally being active.

You’ve probably heard this term before and pieced it together, but for the people who tear their ACL and think “man I can’t believe I have to wait until the surgery to do anything”, prehab is extremely important for setting yourself up for success post-op. It’s an integral part of the overall treatment plan for ACL injuries, aiming to optimize your physical condition before surgery and  can significantly impact the success and speed of post-operative recovery. You can also read more about it on our page here: What is Preoperative Prehabilitation Physical Therapy?

Prehab means getting a head start on doing the things you’d address post-operatively, such as reducing pain and inflammation, restoring (range of motion) ROM and building strength. Getting ahead of the curve with these can make a huge difference in how your rehab journey looks as the quicker you restore your ROM and strength, the better your outcomes will be. Studies have shown that individuals lacking knee extension ROM pre-op were 5 times more likely to continue to lack extension up to 6 months, which can have a huge impact on your walking and running mechanics and lead to other complications down the line1. Other studies have found that individuals with >20% strength deficit relative to their non-operative side before surgery continued to have significant strength deficits up to 2 years post-op.

A systematic review conducted in 2020 found that engaging in prehab protocols that included strengthening, neuromuscular control, balance work, and ROM exercises was correlated with a higher limb symmetry index (LSI), or the ratio between your post-op and non-op side. It’s typically used to compare measures such as strength and jump testing between your legs and is used as a marker for performance and progression. Studies found that the prehab group had a significantly higher LSI in both quad strength and single leg hop testing at 12 weeks post-op compared to the control group. Individuals who underwent prehab were also found to have a higher return to sport rate than those who didn’t3.

Prehab sets the foundation for your ACL reconstruction surgery and post-op recovery, putting you in a better position to return to your previous levels of activity and reduce the risk of re-injury.


One of the biggest early goals in ACL rehab is to restore your full knee mobility with an emphasis on knee extension, or your ability to straighten and lock out your knee. Restoring full ROM and developing control in extension is necessary for walking and running, reducing compensation and strain on other areas that would have to make up for the lack of stability. It’s not enough to settle for hitting 0 degrees of knee extension, as in most cases peoples’ knees hyperextend and go past neutral, so your goal should be to match the other knee’s range of motion as soon as possible.

Knee extension range of motion is also a huge predictor of quad strength, as their primary function is to straighten your knee, but also control your ability to descend stairs, squat, jump, etc. Lacking just 5 degrees of extension was linked to quad weakness and patellofemoral pain, and deficits in knee extension at 4 weeks post-op were correlated with continued loss of extension at 12 weeks4, showing how important it is to get your ROM back as quick as you can to avoid complications later on.


The surgeon might have given you a timeline on when to begin things such as squatting, running, or even returning to sport, like running at the 3-4 month mark, and returning to sport after 6-9  months. The issue with these timelines is they don’t take into consideration what you’re physically capable of at that stage of your rehab, and how different progress can be from person to person. There’s no one size fits all rehab program, so it’s even less likely that everyone will be ready to run or jump at the exact same time post-op.

That’s where having objective measures and benchmarks come into play, letting you know when you’re physically ready to take those next steps and push things in physical therapy. Being able to quantitatively assess how you’re progressing and compare it to the available return-to-sport criteria lets you know when it’s safe for you to dial things up. The last thing you want is to hear “well it’s been 9 months your surgeon said you’re good to go” and your PT sends you back to training without properly assessing.

If your PT is only checking your leg strength by having you kick out into their hand, that should raise some alarm bells. Running, jumping, and cutting all involve significant forces through the quads and knees, so you should have an accurate picture of your strength before attempting them. Dynamometer testing gives actual values to compare your strength and force output side to side and determine your LSI. Most guidelines recommend having >70% LSI for quad strength to return to running6, and >90% LSI in quad strength and hop testing among other considerations for return to sport.

Force plates are another great tool that takes the guesswork out of assessing the quality of your jumps by measuring factors such as force output and loading for each side, as well as eccentric control and deceleration rate. Being able to put numbers to what you’re seeing also means you get to see how you’re progressing in real time, and also make sure you’re checking all the boxes in those return-to-sport criteria. 

This study in 2017 found that a greater proportion of athletes who had >90% LSI on strength testing and single leg hop testing maintained the same level of sports participation 1 year after being cleared to return to sport compared to those who didn’t, with 20% from the second group having experienced a second ACL rupture that contributed to their inability to continue sports participation7.

All of this talk about objective measures and criteria-based guidelines doesn’t mean that following the timeline is inherently wrong, just that it shouldn’t be the only thing you use to judge that you’re ready to get back to competing or being active. A study in 2020 found that young athletes who returned to knee-strenuous sport before 9 months post-ACL reconstruction had approximately 3 to 7 times the rate of new ACL injury compared with those who delayed return to sport until at least 9 months after surgery8. Allowing the body time to adequately heal is important, but we should be considering this in tandem with objective criteria to ensure you can return to sport safely.

If any of this was a wake-up call that you needed to reconsider your current post-op ACL rehab, or you’re feeling concerned about how to find the right PT clinic for you before you start your journey, check out our blog post: “What should you look for in your Physical Therapist?

If you’re interested in working with us to help you safely get back to sports or being active after your ACL surgery, reach out to us today for a free 15-minute discovery call to make sure we’re the right fit for you!


  1. McHugh MP, Tyler TF, Gleim GW, Nicholas SJ. Preoperative indicators of motion loss and weakness following anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther. 1998 Jun;27(6):407-11. doi: 10.2519/jospt.1998.27.6.407. PMID: 9617726.
  2. Eitzen I, Holm I, Risberg MA. Preoperative quadriceps strength is a significant predictor of knee function two years after anterior cruciate ligament reconstruction. Br J Sports Med. 2009 May;43(5):371-6. doi: 10.1136/bjsm.2008.057059. Epub 2009 Feb 17. PMID: 19224907.
  3. Giesche F, Niederer D, Banzer W, Vogt L. Evidence for the effects of prehabilitation before ACL-reconstruction on return to sport-related and self-reported knee function: A systematic review. PLoS One. 2020 Oct 28;15(10):e0240192. doi: 10.1371/journal.pone.0240192. PMID: 33112865; PMCID: PMC7592749.
  4. Noll S, Garrison JC, Bothwell J, Conway JE. Knee Extension Range of Motion at 4 Weeks Is Related to Knee Extension Loss at 12 Weeks After Anterior Cruciate Ligament Reconstruction. Orthop J Sports Med. 2015 May 4;3(5):2325967115583632. doi: 10.1177/2325967115583632. PMID: 26675061; PMCID: PMC4622346.
  5. Sachs RA, Daniel DM, Stone ML, Garfein RF. Patellofemoral problems after anterior cruciate ligament reconstruction. Am J Sports Med. 1989 Nov-Dec;17(6):760-5. doi: 10.1177/036354658901700606. PMID: 2624287.
  6. Rambaud AJM, Ardern CL, Thoreux P, Regnaux JP, Edouard P. Criteria for return to running after anterior cruciate ligament reconstruction: a scoping review. Br J Sports Med. 2018 Nov;52(22):1437-1444. doi: 10.1136/bjsports-2017-098602. Epub 2018 May 2. PMID: 29720478.
  7. Toole AR, Ithurburn MP, Rauh MJ, Hewett TE, Paterno MV, Schmitt LC. Young Athletes Cleared for Sports Participation After Anterior Cruciate Ligament Reconstruction: How Many Actually Meet Recommended Return-to-Sport Criterion Cutoffs? J Orthop Sports Phys Ther. 2017 Nov;47(11):825-833. doi: 10.2519/jospt.2017.7227. Epub 2017 Oct 7. PMID: 28990491.
  8. Beischer S, Gustavsson L, Senorski EH, Karlsson J, Thomeé C, Samuelsson K, Thomeé R. Young Athletes Who Return to Sport Before 9 Months After Anterior Cruciate Ligament Reconstruction Have a Rate of New Injury 7 Times That of Those Who Delay Return. J Orthop Sports Phys Ther. 2020 Feb;50(2):83-90. doi: 10.2519/jospt.2020.9071. Erratum in: J Orthop Sports Phys Ther. 2020 Jul;50(7):411. doi: 10.2519/jospt.2020.50.7.411. PMID: 32005095.

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