Force analysis of the patellar mechanism

Area of Science:

• Biomechanics
• Orthopedic Surgery

Background:

• Patellofemoral joint mechanics are complex.
• Accurate force analysis requires understanding contact surface geometry.

Purpose of the Study:

• To experimentally evaluate a frictionless force analysis model of the patellar mechanism.
• To assess the predictive accuracy of the model based on measured geometric characteristics.

Main Methods:

• Radiographic measurement of contact surface geometry in 42 knee specimens (0-120 degrees flexion).
• Analysis to predict force relations within the patella.
• Experimental measurement of ligamentum patellae and rectus femoris tension ratios during simulated leg functions in 10 specimens.

Main Results:

• The ratio of ligamentum patellae to rectus femoris tension exhibits a complex relationship with knee flexion angle.
• This ratio increases up to 30 degrees, decreases to 90 degrees, and increases again beyond 90 degrees.
• The developed analysis accurately predicts both the pattern and magnitude of this ratio.

Conclusions:

• Accurate prediction of patellofemoral joint reaction forces necessitates incorporating contact surface geometry.
• Surgical procedures like tibial tubercle relocation require considering effects on both patellar mechanism angle and contact geometry for inferring mechanical consequences.