ACL Rehab ... Why 9 months is not long ENOUGH!

ACL injuries are a common injury physiotherapists are reqired to manage in outpatient settings. The rehabilitation is long and the process is far from simple. In this blog we provide an overview of some important issues that you may not have covered at university. We also show how to integrate S&C performance considerations into your physiotherapy practice.

ACL Rehab takes longer than 9 months

Its commonly suggested that ACL rehabilitation is a 9 month process . This idea is somewhat outdated and stemms for the orginal work of the accelerated ACL rehabilitation programmes of the 1980s by Donald Shelbourne. Back then 9 months was indeed ground breaking based upon the best available evidence. But today , it is generally accepted that 12-14 months is more realistic to recover function of all the physical qualities required for high performance in invasion sports such as football and rugby after ACL reconstruction. The need for high levels of maximal strength, rate of force development and skill acquisition to accelerate, decelerate and change direction safely often can not be acheived in 9 months.

This requirement for a longer period of rehabilitation was nicely illistrated in a US study of elite soccer players that has undergone ACLR. The soccer players at 6 months were tested and found to have high levels of muscle strength but poor levels of muscle power or rates of force development (RFD).

Why is this important ?

A common criteria for return to sport is that patients should be able to acheive at least 85-95% maximal muscle strength in the affected limb when compaired of the contralateral limb. However, the time reqired to develop maximal muscle strength in many sporting activities such as a rapid change of direction task is considerably slower. So in a practical sence although the patient might be very strong, they cant produce that strength faster enough when it is needed most!

What did this study find?

Well at 6 months the patient/ athletes maximal quadriceps strength was 97% of their pre injury muscle stength .... which is amazing ! But the athletes power or ( rate of force development ) at 30, 60 , 90 milliseconds ( i.e. their ability to produce high force in under 1 second ) was 80%, 77% and 63% respectively of their preinjury levels. In fact it took over 12 months ( a further 6 months ) for the RFD values on the reconstructed knee to acheive above 90% of their pre injury average values.

What does it mean clinically ...?

1. Well you need to give your ACLR patients and the refering surgeon a healthy dose of expectation management !

2. Patients and clinicans need to understand that ACLR rehabilitation will take over 12 months for those that want to return to invasion sports or activities that require acceleration, deceleration and change of direction at speed.

3. A high level of muscle strength is not enough to return to sport , the muscle and athlete must be physically prepared to produce force at high levels and at very high rates if they are to survive a return to sport!

Why is the speed of contraction important ?

In a study investigating the mechanism of ACL injury in 39 basketball players, speed was an important factor! Based upon video replay of the injury situations the researchers estimated that it took between 17 - 50 miliseconds after a collision with another player ( contact injury) or ground contact and valgus collapse ( non contact ) for the ACL to rupture.

The picture below is taken from the actual study using synchronized videos images. It shows the female player in white in the middle of the images at inital ground contact in image A, image B is taken at 33 milliseconds after initial contact corresponding to the approximate estimated time of ACL rupture. Image C is 133 milliseconds after initial contact ... at which point the damage is already done!

So what ?

Well the so what; is speed of muscle contraction matters! Even if your patient is strong and I mean very strong, if they cant harness that strength quickly then they can not prevent a ACL rupture because the maths dont add up.

For a practical example consider this situation, it has been shown that the average non athletic male takes between 200-300 milliseconds to generate maximal force (strength) in a lab ( I.e. in prefect conditions).

This clearly is too slow to stop a rupture when we know that its been estimated that 50 miliseconds and below is the magic number !

Whats worse !

Yes, it does get worse! We also know that at 2 years there are some patients post ACLR that still display deficits in muscle strength in both the knee flexors and extensors. Now we dont know why this is for sure and there could be several reasons. But to me this means that we need to push patients harder and hold on to them for longer to ensure we do our level best to rectify all their physical imparments.

This is before we sign them off as fit to return to sport or their occupation.

So what can you do ?

1. Improve their skill aquisition for basic movement patterns early in their rehabiltation

2. Get your patients really strong in the clinic and then in the weight room

3. Rehab them to generate high forces fast or ballistically

4. Rehab them to also generate moderate forces very fast

5. Dont forget to work on the skill of change of direction ability

So I hope you can see why 9 months in most cases is just not long enough for ACLR rehabilitation and return to sport or heavy occupational tasks.

As rehabilitation professionals its our job to both educate patients and other healthcare professionals on what GOOD looks like and how long it takes to be GOOD!

Futher reading

Dos’Santos, T., Thomas, C., McBurnie, A., Comfort, P., & Jones, P. A. (2021). Biomechanical Determinants of Performance and Injury Risk During Cutting: A Performance-Injury Conflict? Sports Medicine (Auckland, N.Z.). https://doi.org/10.1007/s40279-021-01448-3

Gokeler, A., Neuhaus, D., Benjaminse, A., Grooms, D. R., & Baumeister, J. (2019). Principles of Motor Learning to Support Neuroplasticity After ACL Injury: Implications for Optimizing Performance and Reducing Risk of Second ACL Injury. Sports Medicine (Auckland, N.Z.), 49(6), 853–865. https://doi.org/10.1007/s40279-019-01058-0

Myer, G. D., Martin, L., Ford, K. R., Paterno, M. V., Schmitt, L. C., Heidt, R. S., Colosimo, A., & Hewett, T. E. (2012). No association of time from surgery with functional deficits in athletes after anterior cruciate ligament reconstruction: Evidence for objective return-to-sport criteria. The American Journal of Sports Medicine, 40(10), 2256–2263. https://doi.org/10.1177/0363546512454656

Shelbourne, K. D., Klootwyk, T. E., & Decarlo, M. S. (1992). Update on accelerated rehabilitation after anterior cruciate ligament reconstruction. The Journal of Orthopaedic and Sports Physical Therapy, 15(6), 303–308. https://doi.org/10.2519/jospt.1992.15.6.303

Sonnery-Cottet, B., Saithna, A., Quelard, B., Daggett, M., Borade, A., Ouanezar, H., Thaunat, M., & Blakeney, W. G. (2019). Arthrogenic muscle inhibition after ACL reconstruction: A scoping review of the efficacy of interventions. British Journal of Sports Medicine, 53(5), 289–298. https://doi.org/10.1136/bjsports-2017-098401

Wright, A. R., Richardson, A. B., Kikuchi, C. K., Goldberg, D. B., Marumoto, J. M., & Kan, D. M. (2019). Effectiveness of Accelerated Recovery Performance for Post-ACL Reconstruction Rehabilitation. Hawai’i Journal of Health & Social Welfare, 78(11 Suppl 2), 41–46.