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Reducing the lateral force acting on the patella does not consistently decrease patellofemoral pressures.

John J Elias1, Jennifer A Cech, David M Weinstein

  • 1Medical Education and Research Institute of Colorado, 3920 North Union Blvd, Suite 210, Colorado Springs, CO 80907, USA. elias@meric.info

The American Journal of Sports Medicine
|July 21, 2004
PubMed
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Patellofemoral treatments aiming to reduce lateral forces may not consistently relieve pain. Modifying the Q angle is more effective than increasing vastus medialis force in reducing patellofemoral pressures.

Area of Science:

  • Biomechanics
  • Orthopedic Surgery
  • Computational Modeling

Background:

  • Extensor mechanism procedures targeting lateral forces on the patella lack consistent pain reduction.
  • Current patellofemoral treatments show variable efficacy due to inconsistent pressure reduction.

Purpose of the Study:

  • To investigate the impact of altering the Q angle and vastus medialis contribution on patellofemoral pressures and forces.
  • To understand the role of moments in patellofemoral pressure variations during flexion.

Main Methods:

  • Computer simulation of four knee models undergoing squatting from 40 to 90 degrees.
  • Simulated interventions included increasing vastus medialis force by 50% and decreasing Q angle to 15 degrees via tibial tuberosity medialization.

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Main Results:

  • Decreasing the Q angle significantly reduced lateral forces from the quadriceps and patellar tendon, proving more effective than increasing vastus medialis force.
  • Both interventions reduced lateral rotational and tilting moments on the patella during flexion.
  • Variations in these moments led to unpredictable increases in patellofemoral pressures in some models.

Conclusions:

  • Treatments reducing patellofemoral subluxation can unexpectedly alter patellofemoral pressures due to rotational and tilting moments.
  • Procedures restoring patellofemoral stability may not guarantee pain relief.