ACL Rehabilitation Timeline: Month 3

I thought at the writing of this post the Patriots would have won their 5th Super Bowl title but fate intervened, the Broncos defensive line played out of their minds, and Peyton Manning now his second ring.  Out here in San Jose California the Super Bowl was the talk of the town since the game was just minutes away in Santa Clara.  The good news is that Brady is looking healthy and is poised for more seasons in the NFL and Dion Lewis will be recovered from his ACL injury.  Speaking of Dion Lewis, he is now 3 months post-op from his ACL surgery.

If you have been following along our yearlong ACL rehabilitation timeline we have covered “prehab”, and months 1 and 2.  This post will describe what to expect in month 3 of ACL rehabilitation.

Graft Healing

As mentioned in the post from month 2, the ACL graft itself is at the weakest point of healing around weeks 10-14.  Cellular growth continues to occur to integrate the new harvested ACL graft into the knee.  This month is a turning point in healing as the ACL graft will now become stronger as the weeks progress.  The graft can start taking high loading forces without as much risk of injury.

You can also breathe another sigh of relief, during month 3, since the risk of infection or rejection of the tissue is greatly diminished.  Any surgery comes with an inherent, small, risk of infection.  The highest risk of infection occurs in the first weeks following ACL reconstruction and diminishes over time.  By month 3 the likelihood of infection inside the knee is minimal.

Pain and Swelling

By this point in your rehabilitation, you should have no pain or swelling at the knee.  Pain and swelling, if present, indicates a functional limitation in movement that is causing overuse of a particular tissue.  For instance, lack of full knee extension (straightening) causes increased pressure on the quadriceps and patellar tendon during walking and results in pain below the knee cap.  Additionally, swelling at the 3 month mark, may be related to multiple factors including limited quadriceps strength, poor lower extremity alignment, quadriceps overuse, and limited range of motion.

If you have been diligent with your rehabilitation and accomplishing the goals of each month then you should be pain free and without swelling by month 3.  These two factors are very important because they become determining factors in progression of the rehabilitation protocol.

ACL Rehabilitation Month 3: Physical Therapy

The goals of rehabilitation at month 3 include:

  1. Ensure full knee extension range of motion
  2. Quadriceps strength at >80% of opposite leg
  3. Gluteus maximus strength >80%
  4. Begin return to running progression without pain or swelling
  5. Begin proprioception exercises

Full Knee Extension is Crucial 

From one week post-op until now, I have been harping on the need to gain full knee extension.  In many ways, full knee extension is initially more important than gaining full knee flexion.  Walking gait, running gait, stairs negotiation, and knee stability all require full knee extension range of motion and control.

Research has been extensive and clear in the association between decreased knee extension and functional limitation.  Lack of knee extension has been linked to arthrofibrosis and poor post-operative outcome.  
What are the best ways to gain knee extension 3 months post-op? Prolonged duration stretching is one of the best ways to improve lack of knee extension.  There are a couple effective ways to do this.  The key is that the duration of stretch lasts minutes and not seconds.  I typically suggest patients remain in this passive stretch for at least 10 minutes to allow tissues around the knee to respond to the stretch.  Shorter duration stretches to achieve knee extension are not successful at this stage of rehab. 
What are some easy at-home ways to perform prolonged extension?

Here is a technique I am partial to although there are many that work.  To perform this stretch you will need a chair, a bench or ottoman, and a backpack with a couple of books inside.  The books should weigh about 5-10 lbs.  While seated on a chair, place your operated leg through the straps of the backpack and then place your heel on the ottoman.  One strap of the backpack should be placed just above the kneecap and the other strap placed just below the knee cap.  In this position the backpack will be hanging below the knee.

You will feel a tug on the knee pulling it into extension.  The key here is to let your knee relax so that over the 10 minutes it gradually moves into greater extension.  You may experience discomfort during this stretch and that is expected.  Remember the goal is to achieve full knee extension to allow rehabilitation to progress and to limit post-operative functional loss.

Perform this stretch 2 times per day for at least 10 minutes for maximum benefit.

Quadriceps strength at 80%

From day one out of surgery we have talked about the importance of quadriceps strength in ACL healing.  The first few months were focused on first activating the quadriceps with quad sets, electromyography biofeedback, and direct stimulation with neuromuscular electrical stimulation.  Now developing true quadriceps strength is the primary goal of rehabilitation.   Why are the quadriceps so important? Those big muscles on the front of your thigh are big for a reason.  The quadriceps muscle group controls knee flexion (eccentrically) and knee extension (concentrically).  These muscles are the primary movers in actions like jumping, squatting, climbing stairs, and running.  Without your quadriceps your knee would either hyperextend on every step or you it would buckle completely and you would fall to the ground.  They provide leg stability, drive, power, and shock control.

From weeks 6-8 through the duration of you rehabilitation quadriceps strengthening will take a front row seat.  The goal at approximately 12 weeks post-op is for the quadriceps to be at 80% of full strength.

This 80% cutoff is specifically chosen for a reason.  At this capacity the quadriceps are able to control knee stability and provide adequate shock absorption to begin a return to running program.  The risk of having limited strength is increased “passive” shock absorption where the bony and ligament anatomy absorb the shock versus the muscular system.
This “passive” shock absorption is a big deal and warrants considerable attention.  Multiple studies have demonstrated an increase in the development of osteoarthritis following an ACL reconstruction.  In fact, a 14 year follow up study of 135 patients demonstrated osteoarthritis was 3x more likely following an ACL reconstruction compared to the subject’s non-operated knees over the same period of time.  Additionally, if there was a meniscus tear that was “cleaned up” during the surgery the risk for arthritis was increased.

As you can see, quadriceps strength is crucial during this phase and the rest of rehabilitation. 

Often I see that patients are progressed into running too soon just because the protocol stated you can run at 3 months.  Medical professional sometimes assume patients are keeping up with the herd and give the “OK” to run without a full biomechanical evaluation.

I will discuss return to running and provide ways to determine if someone is ready to run.
How can you be sure that your quadriceps strength is at 80% capacity? There is really only one surefire way to determine muscle strength and that is through the use of isokinetic dynamometry testing.  Unfortunately this involves a large and very expensive machine which is typically only available at research facilities and hospitals. 

There are, however, more common and cost effective ways to infer quadriceps strength.  Although not as reliable as dynamometry testing, a 1 rep maximum test with a seated leg press may provide a ballpark assessment of strength.  This is not a pure quadriceps test as many more muscles are involved but it does provide an objective measure to compare to the non-operated leg.  A more functional test is the single leg step down test to fatigue.  This test involves both strength and endurance so it is more functional than a true isolated strength test.  This allows comparison of form and reps from side to side.

Manual muscle testing is the most common test although the results are largely determined by the strength of the person performing the test.

The key here is to perform some objective measurable test of strength that is reproducible, before progressing in ACL rehabilitation.  

Gluteus maximus strength at 80%

Sufficient strength in the gluteus muscles is necessary to control lower extremity alignment and the pelvis.  The majority of exercises up to this point in the rehabilitation have been double leg exercises such as squats, bridges, leg presses.  From around week 10 onward, single leg control becomes very important and the focus of exercise.

Single leg exercise prepare the lower extremity for running, jumping, stair climbing, and cutting.  As discussed in previous posts, the gluteus maximus is the prime muscle that provides stability to the pelvis and controls rotation and lateral motions at the knee.  Since we know that ACL injuries occur in positions of knee rotation and valgus collapse we appreciate the importance of controlling these motions.

Signs of gluteus maximus and medius weakness

Again the big goal of month 3 in ACL rehabilitation is the return to running progression.  It is important that the whole kinetic chain from the torso to the toes is ready for this increase in force (up to 3x body weight with running).

We stated earlier the incidence of knee arthritis after ACL reconstruction.  The hip muscles play a role here as well.  If the hip can’t control the alignment of the knee, then increased forces are placed either on the lateral or medial knee structures, meniscus, and patellofemoral joint.  When you combine poor leg alignment and poor shock control you have the perfect storm for knee arthritis.

Testing gluteus maximus strength is similar to testing the quadriceps.  Dynamometer testing is the best way.  You can use manual muscle tests, tensiometer tests, and functional testing.  Unfortunately, there is no weight machine that would allow a 1 rep max test for hip abduction.
Functionally, observation of pelvic control and knee control can help determine strength and utilization of the gluteal muscles.

Return to running progression

Now the big questions that everyone asks after ACL reconstruction.

“When can I run again?”

I treat patients here in Los Gatos and San Jose where athletics is huge and people want to return to conditioning as soon as possible after their ACL reconstruction.  My patients want a definitive answer to this question with a specific date.  I understand since I myself went through the same surgery and asked the exact same question.

The real answer to this question is NOT a specific week post-op or specific date.  Just saying, “The protocol states you can run at 3 months so go out there and give it a try.”  This is not evidence based care.  The decision to start a return to running progression needs to be criteria based.

Criteria to START a return to running progression

Research has provided us a good blueprint to work off to make a sound determination on when to begin a return to running program.  Here are the parameters I look for in my practice.

  1. No pain or swelling at the knee
    1. No pain can be present at rest or with activity such as squatting or climbing stairs
  2. Full range of motion in flexion and extension
  3. Quadriceps strength at >80% of opposite leg
    1. Testing with dynamometer, 1 RM leg press, single leg step down
  4. Gluteus maximus/medius at >80% of opposite leg
    1. This may be deceiving in cases of “non-contact” ACL tears since the opposite hip might be weak as well and therefore does not provide a good comparison
    2. Functional testing may be most beneficial by looking at pelvic control, knee control, and trunk control
  5. Normal walking gait (at 3.5-4.0 mph on level surface and 5-10% incline)
    1. Sufficient knee extension at initial contact
    2. Sufficient loading response
    3. Sufficient knee extension in terminal stance
  6. Proficient at single leg mini hop tests
    1. Able to perform 50 mini hops in place without pain
    2. Able to perform 50 mini hops back and forth over tape without pain

Following this criteria based assessment should ensure those recovering from ACL surgery are ready to start a return to running progression.

Time, distance, and volume considerations for return to running after ACL reconstruction 

Once you have been cleared to begin your return to running it is important that you plan your running schedule for the best transition.

There are hundreds of unique return to running plans based on different injuries.  The Journal of Orthopedic and Sports Physical Therapy suggests this transition protocol.
Progress to the next level when you are able to perform 2 miles of activity without pain.  Perform the program no more than 4 times in 1 week and do not perform workouts back to back.  Also they recommend not progressing more than 2 levels in a 1 week period.

As always pain, swelling, and function is your guide during this phase.  Running through pain and swelling does not help you make a full recovery.  Take the time to transition correctly for the fastest return to sport. 

Proprioception Exercises

As your ACL graft heals and your leg strength improves you will need to develop “control” over your knee.  Typically in physical therapy you perform exercises in a quite environment without much distraction or variability.  This does help initially when learning a new task or movement pattern.  As you progress in month 3 of ACL rehabilitation you will need to add dynamic variable training to your routine.

Evading a soccer defender, shooting a pull up jump shot, spinning around a linebacker during a run all require fast, precise, and powerful motions.  In game situations you do not have time to “level your pelvis, move your knee into position, and align your trunk” before taking action.  These motions have to occur naturally and without thinking.

Proprioception exercises are the key to building a base of stability and motor control for sport.  Proprioception is the ability to sense where your body is in space.  A figure skater for instance can sense how they need to move their body to land a triple axel in the correct position while still in the air.

What are proprioception exercises that align with month 3 of ACL rehabilitation?

  1. Double and single leg stance on a fitter board (with and without ball toss)
  2. Single leg kneeling on a Bosu ball (more gluteal focus)
  3. Double leg squatting on a Bosu ball with external perturbation (someone kicking the Bosu ball to make it wobble requiring you to stabilize)
  4. Romanian dead lifts in single leg with a kettle bell

This is by no means an exhaustive list but gives you an idea what works well for this phase of rehabilitation.

Bring on Month 4

As you progress into month 4 of ACL rehabilitation you will realize the work demands get harder but also more fun.  You will begin to feel like an athlete again as you dribble a ball, kick, and jump.  I remember between months 3-4 I finally felt like I was going to make it out and get back to football.  Hope is a great and powerful force that you should harness.  Find positive people in your life and hang out with them.  They will be your energy to put in the hard work now.  Stay tuned for more play by play information in month 4 of ACL rehabilitation!
If you live in San Jose, Los Gatos, Campbell, or Almaden California and want to transition back to running after your ACL reconstruction or want to work with me for your rehabilitation please call my office 408-784-7167.  You can also email me with the address

Written by:
Kevin Vandi
Physical therapist San Jose, Los Gatos, Almaden, Campbell