The goal with the initiation of rehabilitation for an ACL (Anterior Cruciate Ligament) surgery is to prevent what happened to happen again. Rehab should integrate both prevention and performance throughout the entire recovery process—and beyond. Understanding the potential causes of an ACL injury gives us guidance and direction with respect to exercise prescription and progressions.

Understanding the dynamic anatomy of the ACL provides further insight with respect to what ultimately causes it to tear.

Keep reading to learn more.

Why Does the ACL Tear?

The ACL is considered a proprioceptive device and is filled with Golgi Ligament Endings. These ligament endings provide immediate stimulus and musculature that protect the ACL. Notably, it is not designed to be an end range restriction.

The two primary motions of the knee that stimulate the ACL are internal rotation (transverse plane) and abduction (frontal plane). These two motions of the knee are normal and are essential for facilitating an effective and efficient lower extremity for all types of sports and activities.

However, these two motions, if excessive and not controlled, are the same motions that will ultimately cause the ACL to tear. Therefore, internal rotation and abduction of the knee—the right amount at the right time—are necessary for a healthy knee, healthy foot, and healthy hip. But, as with many motions throughout the body, too much of a good thing is a bad thing. In this case, too much internal rotation and abduction not being controlled is a bad thing that results in the ACL being torn.

Before You Rehabilitate the ACL, Understand how the Knee Functions

The key question is this: What creates internal rotation and abduction of the knee? The simple answer is gravity, ground reaction force, mass, and momentum. 

Knowing we need internal rotation and abduction of the knee; the follow-up question then becomes: What controls internal rotation and abduction of the knee? We have the constant and aggressive forces of gravity, ground reaction force, mass, and momentum creating a stimulus to the ACL to allow the proprioceptors of the ACL to do its thing: Turn on as many muscles that control and decelerate internal rotation and abduction.

During function, every muscle group in the lower extremity, the trunk, and the other lower extremity contribute to controlling internal rotation and abduction of the knee. Because gravity, ground reaction force, mass, and momentum are the forces that cause motion in the knee, all our locomotor muscles synergize to control and take advantage these elements to control knee motion. We consider all these muscles as friends of the knee, especially friends of the ACL.

Understand the “Friends of the Knee” for Effective ACL Rehab

The function of the human body, in many ways, reflects the function of life itself. Sometimes, because of how life gets in the way, our friends let us down. Sometimes, because of how our body functions, our friends let it down. And often, it is our friends who are closest to us. The same thing happens with the knee and the ACL. Because of the tremendous force of gravity, ground reaction force, mass, and momentum, it takes all the friends of the knee and ACL to help control these normal motions.

So, who are the closest friends of the knee and ACL? We don’t have to go so far to find them. In fact, we simply go to the “proximal knee” and to the “distal knee.” The proximal knee, of course, is the proximal part of the femur—the hip. The distal knee is the distal part of the tibia—the foot and ankle. It is the muscles of the hip and the muscles of the foot and ankle that are the best friends of the knee and ACL.

When we walk, as we reach out to take a step, the foot reacts to the ground. When the foot strikes the ground, it must deal with the forces of gravity, ground reaction force, mass, and momentum. These forces quickly transform up into the knee and hip.

At the foot, these forces cause subtalar eversion and abduction, as well as ankle dorsiflexion, thus “unlocking” the midtarsal joint. At the hip, these forces cause flexion, adduction, and internal rotation. At the knee, these same forces case flexion and—you guessed it—abduction and internal rotation!

All the motions turn on the multitude of proprioceptors. These proprioceptors transduce what they sense into electrical signals that turn on all the muscles of the lower extremity. All these muscles come together to eccentrically control the motions that are caused by gravity, ground reaction force, mass, and momentum. This includes the motions at the knee.

Therefore, Phase 1 of any prevention, performance, and rehabilitation program should emphasize the control of these motions. We initially keep the demand low and create an integrated movement, so all the friends are helping each other functionally. In other words, we design and manage movements that facilitate minimal amounts and small stresses of hip flexion, adduction, and internal rotation, as well as ankle dorsiflexion and subtalar eversion and abduction.

Early on, the safest and most productive movements emphasize what the hip needs to do to protect the knee. If we can create hip flexion, adduction, and internal rotation while limiting or even reversing the gravity, ground reaction force, mass, and momentum induced motions of the knee, we have created the most aggressively safe excursions possible for the knee.

RELATED: The ACL Misunderstood: Why ACL Tears and Injuries Are So Common

Use 3DMAPS® to Guide Your Knee-Strengthening Exercises After ACL Surgery

So, now onto the title of the blog as the conclusion: What are the three exercises to strengthen the knee after an ACL Surgery? It is best to go directly to 3DMAPS® (3D Movement Analysis and Performance System).

In six simple, successful, and functional movements, 3DMAPS facilitates motion in all three planes of motion of primary joint complexes of the body. The hip is certainly a primary complex, so which of the six movements facilitate hip extension, adduction, and internal rotation? The Posterior Chain Reaction®, Opposite Side Lateral Chain Reaction®, and Opposite Side Rotational Chain Reaction®.

These three movements can then be tweaked to reflect the most aggressively safe excursions possible for the knee, as our vlog talks and moves you through.

Grow Your Skills With 3DMAPS

At Gray Institute, the truths of human movement guide our approach to function, healing, and training. When we understand the body’s natural Chain Reactions, we can better understand and rehabilitate our patients and clients after things like an ACL tear, surgery, or other dysfunction.

If you’re interested in deepening your understanding and growing your skills as a movement professional, check out our 3DMAPS course and free course webinar, available through the Gray Institute App

Build Your Understanding of the Body’s Chain Reactions at Gray Institute

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