Here is the situation. Running is an incredible activity and sport. The health benefits to running far outway any potential risk, but why is it that runners are so often injured? Since the pandemic, running has boomed with an estimated 50 million participants in the U.S. alone (Livestrong.com). The British Journal of Sports Medicine suggests that nearly 80% of runners experience lower leg pain or injury with 50% of them being the knee. Hence, The 5 Biomechanical Reason Runners Have Knee Pain.

Before we dive into photos and videos let’s dissect “Biomechanics”. For all intents and purposes for this blog, “Bio” = biology/anatomy/physiology and “Mechanics” = physics as it applies to the aforementioned human body. We will discuss how stress and strain, forces, torque, and lever arms impact bones and cartilage, muscles and tendons, and lastly, ligaments.

Stress = Force per unit area in response to load.

Strain = Deformation or change of structure in response to load. (Insert equation)

Force = A quantity or measurement that can cause a change in speed, position, or direction of movement. A ground reaction force simply is a vector with magnitude and direction equal and opposite to that which was applied to the ground.

Torque = Internal torque is a muscle that pulls on a joint and causes a bone to rotate around an axis. External torque would be an outside force, such as gravity, causing a joint to rotate to absorb the load.

Lever Arm = The longer the lever arm, the higher the torque.

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Putting it all together: Stress and strain often occur together and increase together. The greater the amount of force over the smaller amount of area will create the highest stress and potential strain. Bones and cartilage, for example, have poor shock resistance and are impacted heavily with high impacts or rate of loading. Muscles and tendons are affected with high joint torques while ligaments are mostly disrupted with abnormal joint frontal and/or transverse motions. This information will come in handy as we discuss the 5 Biomechanical Reasons Runners Have Knee Pain:

1. Genu Valgus (“Knocked Knee”):

Areas of Pain:

• Lateral joint line
• Distal IT band
• Medial border of Patella

Causes of Stress/Strain:

• Inactive or Weak Glute Medius/Maximus
• Weak Posterior Tibialis
• Stiff ankle
• Femoral anteversion

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2. Genu Varus (“Knee Out”):

Areas of Pain:

• Medial joint line
• Lateral border of patella
• Distal IT band

Causes of Stress/Strain:

• Quad dominance
• Medial joint space narrowing (arthritis)
• Inactive or Weak Glute Medius/Maximus

3. Triple Extension Deficit:

Areas of Pain:

• Patella Tendon
• Middle of Patella
• * Achilles Tendon

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Causes of Stress/Strain:

• Inactive or weak Glute Maximus
• Motor control deficit
• Weak Solueus/Gastroc complex

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4. Hip Drop:

Areas of Pain:

• Medial Joint Line
• Lateral Joint Line
• Medial border of patella
• Lateral border of patella
• Pes Anserine
• Distal IT band

Causes of Stress/Strain:

• Inactive or weak Glute Medius/Maximus
• Inactive or weak Obliques
• Inactive or weak Multifidi/Rotatores.
• * Often all occur together

5. Excessive Load:

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Areas of Pain:

• Swelling in knee
• Circumference of knee
• Patella Tendon
• * Hip
• * Low Back

Causes of Stress/Strain:

• Inactive or weak Glute Medius/Maximus
• Weak Quadriceps
• Low back stiffness/pain
• Hip Immobility  
• Weak deep core
• Pelvic floor dysfunction

A few takeaways: Every action has an equal and opposite reaction. Your running form matters. Strength matters. Be fit to run, do not run to get fit. It is ok to lift weights and run as long as your “mechanics” are such that limits or improves upon the list above. If you are unable to identify the biomechanical deficit, get a running assessment. The research and technology available to identify running problems is increasing with every year that goes by. With the innovative advancements in assessing the root cause, treatments are vastly improving as well. What used to be a shotgun approach to treating runners is now a laser. Whatever you do, know that running is good for you! Do not give it up.