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  • Mick Hughes

ACL Rehab: Make it EPIC!

EPIC is probably the least likely word one would use to describe ACL injury and ACL rehab, but EPIC is the word you should start getting familiar with, particularly if you want to reduce the chances of you or your patient sustaining a 2nd ACL injury.

When I refer to EPIC however, it isn’t to the usual reference of EPIC being “remarkable" or "impressive”. In this instance, EPIC stands for Estimated Pre-Injury Capacity (EPIC), and has been shown in a recent study to be more sensitive in predicting 2nd ACL injuries than the usual method of Limb Symmetry Index (LSI) (Wellsandt et al., 2017).

In a study of 70 ACL reconstructed (ACLR) patients (mean age 26yrs, 68%M, 32%F), the authors performed strength and hop tests on the patients pre-operatively on their uninjured leg and used that as a reference point for future testing (EPIC), as well doing the standard LSI testing (injured leg vs uninjured leg) at a minimum 6 months post-op.

The reason the authors chose to do the EPIC testing was because it is widely accepted that bilateral muscle strength and function deficits exist after ACL injury, and the authors question the validity and accuracy of predicting future ACL injury by using the LSI.

So what the authors did, looked like this:


- Quad Strength: Injured Leg (6 months post-op) / Uninjured Leg (Pre-op; 1.5 months post-injury) x 100

- Hop Tests: Injured Leg (6 months post-op) / Uninjured Leg (Pre-op; 2 months post-injury) x 100


- Quad Strength: Injured Leg (6 months post-op) / Uninjured Leg (6 months post-op) x 100

- Hop Tests: Injured Leg (6 months post-op) / Uninjured Leg (6 months post-op) x 100

*Note: >90% EPIC and LSI values were used as a goal to assist in return to sport decision-making


At 2 year follow up the authors found the following:

  • At 6 months post-op; only 28% of patients met >90% EPIC criteria on all the strength and hop tests, however 57% achieved >90% LSI criteria on the strength and hop tests

  • 11 of the 70 patients (15%) sustained a 2nd ACL injury during the 2 year follow up period

  • 8 out of the 11 passed the >90% LSI criteria on all strength and hop tests at 6 months post-op

  • 6 of these 8 however, did not pass the >90% EPIC criteria on all strength and hop tests at 6 months post-op

  • Conclusion: >90% EPIC criteria was superior in predicting 2nd ACL injuries than the current method of >90% LSI

  • EPIC: sensitivity 81%, specificity 30%

  • LSI: sensitivity 27%, specificity 54%

This is a really interesting study with some very important clinical implications that suggest that we may be currently over-estimating ACLR patient’s strength and functional ability by using their post-op test scores as a reference point, and not pre-op test scores when the patient was more likely to be at their fittest and strongest.

And this makes absolute sense. Just think about it for a second; most ACLR patients aren’t able to perform high demand tasks like running and jumping until at least 3 months post-op (and some have to wait much longer than that!). The global de-conditioning that occurs to the body during this 3-6 month period of decreased physical activity certainly would affect the strength and power output of BOTH limbs at the time of post-op testing.

So if a person was able to do a 1.5m single leg hop on both limbs pre-injury when they were fit and healthy, then why should we accept that a LSI of 90% at 1.2m single leg hop distance is ok at 6, 9 or 12 month post-op? It isn’t ok and it’s not good enough. We should be ensuring that we get our ACLR patients back to a level better than their previous best on many strength, power, agility and fitness outcome measures.

Take home messages:

1) This is another great example of pre-op physiotherapy for ACLR being extremely important in acheiving good post-op ouctomes. For those that are considering returning to sport following ACLR this process, pre-op physio and pre-op testing should be considered a non-negotiable.

2) Take the guessing game out of return to sport decision-making, and don’t accept that what the patient can do at 6, 9 and 12 months post-op is their personal best or previous best. Gather as much information as you can pre-operatively, and use that as a baseline for future reference.


Wellsandt, Failla & Snyder-Mackler (2017). Limb symmetry index can over-estimate knee function after ACL injury. Journal of Orthopedic Sports Physical Therapy: 47 (5), 334-338.


For more on all things ACL injury, download my ACL rehab guide by clicking here, and/or watch my online ACL tutorials by clicking on the following links:

1) (delayed access, password required)

2) (instant access)

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