How to get Extension back after your ACLR

Are knee extensions safe after ACLR surgery? YES.

It is an old point of view that knee extensions after an anterior crutciate ligament surgery will strain the graft.

We now know that walking places MORE strain on the ACL than knee extensions. As usual, you should always speak to your physio and surgeon for individualized recommendations.

Knee extension is an important part of ACLR rehab as it helps to improve quads strength functional activities, and subjective function.

Previously, rehab didn’t think open kinetic chain exercises were safe – think sitting and straightening your leg into the air, or a knee extension machine type exercise.

Patients may start open kinetic chain exercises in limited range of motion from the fourth week after surgery without compromising knee stability. Studies have shown that full active knee extension can be achieved in approximately four weeks – a big ask but consistency can make it happen!

Various levels of ACL Strain during other activities:

  • Walking (midstance and late swing phase) – 13%
  • Open kinetic knee extension from 90-0 degrees – 3.8%
  • Lachman’s test (checking the integrity of the ACL) – 3.7%
  • Open kinetic knee isometric at 15 degrees – 4.4%

Knee extension exercise should be considered safe if patients are immediately walking after ACLR or performing closed kinetic chain (CKC) exercise, as OKC exercise results in approximately one-third of the strain observed during walking.

It is recommended to monitor for anterior knee pain and adjust the knee load and the progression of strengthening accordingly – so check with your physio!

This is a guide provided by the research team that explains progressions for knee extensions. I highly recommend having your physio prescribe these, as every ACLR case is slightly different and you want to make sure you are doing the best things for YOUR knee.

You can purchase the ACL Injuries ebook where I talk about my experience, what to expect, graft options, how to find a physio, the mental aspect of the injury, and physical timelines to expect during recovery.


Kotsifaki, R., Korakakis, V., King, E., Barbosa, O., Maree, D., Pantouveris, M., … & Whiteley, R. (2023). Aspetar clinical practice guideline on rehabilitation after anterior cruciate ligament reconstruction. British Journal of Sports Medicine.

Brinlee, A. W., Dickenson, S. B., Hunter-Giordano, A., & Snyder-Mackler, L. (2022). ACL reconstruction rehabilitation: clinical data, biologic healing, and criterion-based milestones to inform a return-to-sport guideline. Sports Health, 4(5), 770-779.

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