Quadriceps Strength – ACL Injuries

Running, Knee, Uncategorized, Blog, / By Koh Peh Chia

In the final post of this ACL series, we look at an important determining factor, quadriceps strength, which affects your recovery and chances of re-injuring the knee again. This is factor stands out amongst the others we have mentioned. Therefore, we will explain more about how you and your physiotherapist can address this issue.

Why Is the Quadriceps Strength Important?

In a 2016 study about ACL reconstruction, the authors found that of patients who had less than 90% of comparable strength to the uninjured leg, 33% of them re-injured their knee again. However, what was more interesting was that for every 1% less than 90% of comparable strength, this was equivalent to a 3% increase risk of further injury of the knee.

How Do I Tell the Difference?

For you to quantify your leg strength, your physiotherapist has to calculate the maximum single leg strength of the injured leg over the non-injured leg. You can than multiply this number by 100 and that results in a number. It is recommended that this number be at 90 for it to be satisfactory. This means that the injured leg has to be at least 90% as strong as the uninjured leg.

What Can I Do To Improve It?

If your quad strength is lacking, together with your physiotherapist, you can use exercises that target single leg strength. Here are some examples below:

  1. Lunge

2. Leg Extension

3. Split Squat

Your ACL rehabilitation journey is an individual and unique process. It is important to address the quadricep strength as part of the process to allow for optimal recovery.

If you have any more questions or would like our physiotherapists to assess or treat your ACL injury, feel free to drop us a question, talk to us, or fill in the form below. Do check out our Instagram page too.

Winsen Citra

Principal Physiotherapist

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Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016 Jul;50(13):804-8. doi: 10.1136/bjsports-2016-096031. Epub 2016 May 9. PMID: 27162233; PMCID: PMC4912389.

Hughes, M. (2021). Why Quads Matter in ACL Rehabilitation. Retrieved from

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