Effect of change in patellofemoral joint contact area by the decrease in vastus medialis muscle activation on joint...

Area of Science:

• Orthopedics
• Biomechanics
• Sports Medicine

Background:

• Patellofemoral pain syndrome is a prevalent orthopedic condition in runners.
• The precise relationship between vastus medialis (VM) activation, knee joint mechanics, and patellofemoral joint stress (PFJS) remains unclear.

Purpose of the Study:

• To investigate how reduced VM activation affects PFJS.
• To explore the impact of altered patellofemoral joint contact area on PFJS.

Main Methods:

• A patellofemoral joint (PFJ) sagittal model was employed to quantify PFJ reaction force and PFJS.
• Mathematical modeling simulated knee joint flexion angles (10-45°) and extension moments (0-240 Nm).
• PFJS was compared under normal VM activation (NC) and decreased VM activation (DC) conditions.

Main Results:

• PFJS was consistently higher under decreased VM activation (DC) compared to normal VM activation (NC) across all simulated ranges.
• Maximum PFJS values were observed at maximal knee flexion angles and extension moments in both conditions (NC: 14.9 N/cm², DC: 16.4 N/cm²).

Conclusions:

• Reduced VM activation may play a role in the development of patellofemoral pain syndrome.
• Clinicians can consider strategies to enhance VM activation to manage pain in patients with this condition.