29/06/2025
🦵 Why Deep Squats Aggravate Patellofemoral Pain
🔺 1. Excessive Patellofemoral Joint Reaction Force (PFJRF)
• As knee flexion increases (especially past 60°), the contact area between the patella and femur increases, but the compressive force rises even faster.
• At 90° of flexion, the PFJRF can be 6–7 times body weight.
• This dramatically increases hydrostatic pressure within the joint — and while mild HP is chondroprotective, **excessive HP may lead to:
• Subchondral bone stress,
• Intraosseous hypertension,
• Pain from activated nociceptors**【Sheehan et al., 2016】.
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💥 2. Increased Octahedral Shear Stress (OSS) at the Cartilage Interface
• During deep squats, malalignment (e.g. patellar tilt, femoral internal rotation, or valgus) amplifies OSS at the patellar cartilage.
• OSS is strongly linked to:
• Cartilage matrix breakdown,
• Nitric oxide and inflammatory cytokine release from chondrocytes【Smith et al., 2000】.
• These stresses are worse in flexion due to the smaller, less congruent posterior patellar contact zone engaging with the femoral trochlea.
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⚠️ 3. Poor Neuromechanical Control at High Flexion
• Many patients with PF pain have:
• Delayed or underactive vastus medialis obliquus (VMO),
• Hip weakness or dynamic knee valgus,
• Poor proprioception.
• These deficits lead to abnormal tracking, worsening mechanical stress and increasing shear.
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🔬 4. Reduced Load-Sharing Through Other Tissues
• In high degrees of knee flexion:
• The quadriceps tendon compresses into the femur,
• The load is disproportionately shifted into the patellofemoral joint rather than shared through other soft tissues (e.g., ITB, hamstrings).
• This means that target tissues receive excessive force, especially in the lateral facet of the patella, a common site of degeneration.
