3 mistakes blog cover (1)

3 Common Mistakes Physios make when it comes to ACL Rehab.


One of the biggest mistakes someone can make Post-ACL Reconstruction is returning to sport too early! There is evidence that suggests that for every month that return to sport was delayed, until 9 months after ACL reco, the rate of a knee injury was reduced by 51%! (Grindem et al. 2016, Barber-Westin & Noyes. 2011) Now I know some of you may argue everyone is different and it should be treated from an individual basis, which yes is true. However, do you really think 9 months is long enough for adequate rehab? There have also been debates as to whether we should delay RTS up to 2 years post reco. (Nagelli & Hewitt 2017). Given what we know so far, I will argue that nobody should return to sport before 9 months.


There seems to be a lack of specificity when it comes to muscle strength training post-op. We know in the literature that immediately after an ACL injury occurs, even before reconstruction, a myriad of negative outcomes occur within the knee extensor muscle that compromises the restorative capacity and plasticity of skeletal muscle. (Fry et al. 2017) More recently, there is literature to show impairments in neuromuscular cortico-spinal excitability even 2 years after the injury! (Norte et al. 2018) What this means is that right after the injury, there are changes both in the tissue and neuromuscular level that already put you in a disadvantage to rehab!

So if we know this is happening, why are we not being specific in choosing our exercises! From all the evidence we know, Quad Strength Symmetry is an important predictor of knee re-injury (Grindem et al. 2016, Ithurburn et al. 2017, Schmitt et al. 2015).

Let me simplify it more:

1) We know that Quadriceps Strength Symmetry is an important predictor of re-injury so therefore we should strengthen it.

2) What is the most effective way to target a specific muscle? SPECIFICITY. How can we be specific in targeting a muscle? Use an ISOLATED exercise – (i.e. Open Kinetic Chain Knee Extension). Yes, I said an OKC exercise. Let me just stop you before you say anything about tearing a graft because of the shearing force as commonly taught by entry-level universities (Henning et al. 1985).

There are numerous studies that show no difference in anterior tibial laxity, patient-reported or physical function with an early or late introduction of OKC exercises in the ACL Reco population when compared to CKC exercises. However, I would restrict the ranges to 90°-40° from 4-12 weeks and a full range of motion at 12 weeks based on the design used in these studies. (Perriman et al. 2018, Barcellona et al. 2015, Fukada et al. 2013). Some may argue that you are strengthening your quadriceps when you are doing these so-called “functional” CKC exercises. Yes, this is true, but can you really tell if the quad is working? Can you be confident that the glute or hamstring or other muscles are not compensating and really “masking” the quadriceps from activating?

I am not saying to ditch CKC exercises, in fact, these should be the core of your rehab (heavy squats, deadlifts, etc.) but rather to keep in mind that OKC can greatly improve your rehab due to the isolation and specificity. We haven’t even begun to discuss speed and force generation of the quadriceps; that would be in another blog.


Another big mistake some physios make is using time-based criteria to progress someone to the next phase of rehab rather than functional based criteria. One great resource to use in terms of general guidelines is the MOON Group’s ACL Rehab Guidelines.

In one study, there was an estimated 84% lower knee re-injury rate in patients who passed certain RTS criteria. (Grindem et al. 2016) The RTS criteria used in the study were:

1) Quadriceps Strength Symmetry Index >90% (I would even argue that you need to be closer to 95-100% as the study showed a 3% reduction in a knee injury for every 1% increase in Quad Index).
2) Tests from the Limb Symmetry Index >90% (Single Hop for Distance, Triple Crossover Hop, Triple Hop, 6m Timed Hop)

Now, I am not advocating that if you pass the above criteria that you are 100% ready to return to sport as there is still a lack of consensus on what the best objective RTS criteria (Wellsandt et al, 2017) However, what I am saying is that if you FAIL these RTS criteria, you are DEFINITELY not ready to return to sport!

Another limitation is how we measure these results. For example, if we look at Quadricep Strength Symmetry, how can you confidently say that what you are measuring is accurate? Unless you have a $50,000 isokinetic machine at your clinic, chances are you won’t be! Even if you measure quad strength using a handheld dynamometer and the results show symmetry, chances are you are still way off! (Sinacore et al. 2017)


1) Don’t return to sport before 9 months (Some may argue even up to 2 years but that’s another discussion)
2) Be specific with strengthening. Isolate the Quadriceps and don’t be afraid to use OKC exercises!
3) Be as close to 95-100% to the RTS Criteria in terms of Quad Strength and Limb Symmetry Index.

I haven’t even discussed the psychological barriers/self-reported confidence to RTS aspect (That will be another blog).

Leave your comments below and let us know what you think!


Barber-Westin and Noyes (2011). Factors used to determine return to unrestricted sports activities after anterior cruciate ligament reconstruction. J.Arthro

Barcellona et al (2015). The effect of knee extensor open kinetic chain resistance training in the ACL-injured knee. Knee Surg Sports Traum Arthro

Fry et al (2017). ACL injury reduces satellite cell abundance and promotes fibrogenic cell expansion within skeletal muscle. J Orthop Res

Fukuda et al (2013). Open kinetic chain exercises in a restricted range of motion after anterior cruciate ligament reconstruction: a randomized controlled clinical trial. AJSM

Grindem et al (2016). Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. BJSM

Henning et al (1985). An in vivo strain gage study of elongation of the anterior cruciate ligament. AJSM.

Ithurburn et al (2015). Young Athletes With Quadriceps Femoris Strength Asymmetry at Return to Sport After Anterior Cruciate Ligament Reconstruction Demonstrate Asymmetric Single-Leg Drop-Landing Mechanics. AJSM

Nagelli and Hewitt (2017). Should Return to Sport be Delayed Until 2 Years After Anterior Cruciate Ligament Reconstruction? Biological and Functional Considerations. Sports Med

Norte et al (2018). Quadriceps Neuromuscular Function in Patients With Anterior Cruciate Ligament Reconstruction With or Without Knee Osteoarthritis: A Cross-Sectional Study. J Athle Train

Perriman et al (2018). The Effect of Open- Versus Closed-Kinetic-Chain Exercises on Anterior Tibial Laxity, Strength, and Function Following Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis. JOSPT.

Schmitt et al (2015). Strength Asymmetry and Landing Mechanics at Return to Sport after Anterior Cruciate Ligament Reconstruction. Med Sci Sports Exerc

Sinacore et al (2017). Diagnostic Accuracy of Handheld Dynamometry and 1-Repetition-Maximum Tests for Identifying Meaningful Quadriceps Strength Asymmetries. JOSPT

Wellsandt et al (2017). Limb Symmetry Indexes Can Overestimate Knee Function After Anterior Cruciate LigamentInjury. JOSPT


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