Returning to Running After ACL Surgery – Four Pines Physical Therapy
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Returning to Running After ACL Surgery


ACL tears are one of the most common knee injuries sustained while skiing. With the heavy snow, good skiing, and epic power days this year, I’m sure there was no shortage of knee injuries. While I hope everyone had a safe and healthy season, I know some individuals’ ski seasons ended in a less than ideal manner.

If you tore your ACL this year, sometime in January or February, you are likely sitting right about 3-4 months out of surgery. My guess is you are finally starting to feel better, your knee is getting stronger, and you are longing for the snow to melt. You are anxious to get back to biking, hiking, and running.

Can’t blame you there!

However, when returning to running after an ACL reconstruction there are several things to consider for a safe, effective, and successful progression back.



As rehab professionals, we look to return someone to running at right about 16 weeks. Yes, graft type, prior surgery, and other factors do make a difference, but overall 16 weeks is about what you’re looking at. Why so long? It takes (at least) this amount of time for your knee joint to start to normalize, re-establish homeostasis, and build back up protective strength.

In fact, recent studies are showing that it takes 2 years for all healing markers to return to normal and homeostasis to fully be re-established in the knee, but that’s another discussion.

Now, not to get too medical, there are some things to consider from a tissue healing standpoint before beginning a running program. After surgery, your graft goes through a process called ligamentization where the graft (usually from a hamstring, quad, or patellar tendon) becomes a ligament through revascularization, cellular regeneration, and remodeling of the tissue. Either end of the graft must become incorporated into the insertion sites and build tensile strength.

This process doesn’t fully occur until 12 weeks.


Normal Joint Motion

Since day one you have likely been working on the range of motion and swelling in your knee. Working to re-establish normal motion and mechanics in the knee early on is essential for long term joint health.

Making sure you have full knee extension (all the way straight) and knee flexion (bent) equal to the other side is pivotal before beginning a running program.

Swelling is another key issue. While swelling after surgery is normal, constant swelling 16 weeks out indicates the joint is still irritated. Running will increase the forces through the knee joint and the last thing you want to do is pound on an already cranky joint.



Quad strength is the most important factor in protecting your knee and getting you back to functioning at full force. Don’t get me wrong, hamstrings (another huge protector of the ACL) and glutes are super important, but quads are key. The quads provide strength and stability to the knee, protect it, and take load off of the joint. Time and time again, research has shown quad strength matters… a lot. So how does this play into running?

Ideally at 4 months, your quad strength on the injured side should be 60% of the uninjured knee.

That is to say, if you can kick out 100lbs on a knee extension machine on your good side, you should be able to kick out 60lbs on your surgical side before we even consider letting you run. Why? This shows you have good enough protective strength in the knee to allow for initiation of a safe running program.



 Along with quad strength, balance (specifically the neuromuscular control portion) is critical in prevention of future injury and overall joint health.

Several studies coming out recently have emphasized the importance of re-establishing complete motor control, balance, and stability for injury prevention.

There are several ways in which balance can be tested. One of my favorites and most researched in terms of ACL recovery is called the Y-balance. The test incorporates balancing on one leg while reaching the other leg into three different directions. Both legs are tested and the results compared. At 4 months, results on the surgical leg should be within 90% of the uninjured leg. This number has been shown to be an acceptable cutoff for reduced injury risk and assumption of a safe return to running program.



If you are anything like me, once cleared to run, the most challenging part is not over doing it. However, it is extremely important to progress back slowly and only manipulate one variable at a time.

Usually after ACL injury, return to running programs begin with a 10-15 min easy run on flat, dry ground, 3 days per week. Each week, running time is progressed. Once 25-30 min of consistent running is obtained without any symptoms, another variable can be manipulated (speed, frequency, terrain, or intensity).

When progressing back into running some general guidelines to remember are

  1. 1
    Do not progress distance more than 10% per week
  2. 2
    Take a rest day between runs when just starting back
  3. 3
    Avoid over striding as this increases joint forces at the hip, knee, ankle, and low back. Try opting for a quicker cadence (step rate) at the same speed.

Running programs will vary and some will progress slower depending on the extent of the surgery, prior history, and training experience.

Not sure if you are ready?

Contact us for a Running Assessment or a Functional Movement Assessment in either the Alpine or Jackson location and we’ll be sure to get you off on the right foot!

Kaysha Heck

Kaysha Heck

Kaysha is a native of Washington State where she spent the majority of her time either outside or in the gym training as a high level competitive gymnast. She went on to compete collegiately for Seattle Pacific University where she earned both academic and athletic honors. She completed her physical therapy education at Regis University in Denver, CO before pursuing Residency Training in Sports Physical Therapy at the University of Florida. Even after her competitive career was over she has remained involved in the sport of gymnastics motivating, coaching, researching, and working to educate athletes, coaches, parents, and providers. Kaysha is an outdoor enthusiast and enjoys being challenged by new athletic endeavors.
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