1. Returning to sport too early!

One of the biggest mistakes someone can make Post-ACL Reconstruction is returning to sport too early! There is evidence that suggest that for every month that return to sport was delayed, until 9 months after ACL reco, the rate of knee injury was reduced by 51%! (Ref:  Here, and Here) 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 has also been debates as to whether we should delay RTS up to 2 years post reco. (Ref: Here). Given what we know so far, I will argue that nobody should return to sport before 9 months.
 

2. Lack of specificity in muscle strengthening (Especially the Quadriceps!)

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. (Ref: Here) More recently, there is literature to show impairments in neuromuscular cortico-spinal excitability even 2 years after the injury! (Ref: Here) 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. (Ref: Here, Here, Here)

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 - (ie. 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. (Ref: Here)

There are numerous studies that show no difference in anterior tibial laxity, patient reported or physical function with 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 full range of motion at 12 weeks based on the design used in these studies. (Ref: Here, Here, and Here). 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 about speed and force generation of the quadriceps.... but that would be in another blog)

3. Time-based criteria progressions vs functional-based criteria progressions.

Another big mistake some physios make is using a time-based criteria to progress someone to the next phase of rehab rather than a 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. (Ref: Here) The RTS criteria used in the study was
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 knee injury for every 1% increase in Quad Index) Ref: Here
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 is. (Ref: Here) 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 wont be! Even if you measure quad strength using a handheld dynamometer and the results show a symmetry, chances are you are still way off! (Ref: Here)

In Summary

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)

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