Pilot validation study on a quasi-static weight-bearing knee rig

Area of Science:

• Biomechanics
• Orthopedics
• Knee Joint Research

Background:

• Understanding patellofemoral joint (PFJ) mechanics is crucial for diagnosing and treating knee pathologies.
• Existing methods for studying PFJ kinetics in cadavers have limitations in simulating physiological loading conditions.
• Investigating the impact of pathologies and surgical interventions on PFJ function requires reliable experimental models.

Purpose of the Study:

• To introduce and validate a novel quasi-static knee rig for investigating cadaveric knee biomechanics.
• To assess the repeatability and reliability of the developed knee rig in simulating squatting motion.
• To establish the rig's capability in measuring patellofemoral contact area and pressure under simulated physiological loads.

Main Methods:

• A quasi-static knee rig was developed to simulate knee flexion-extension under body weight.
• Cadaveric knees underwent four repeated flexion-extension cycles with controlled quadriceps and ground reaction forces.
• Patellofemoral contact area and pressure were measured throughout the squat simulation using the rig.

Main Results:

• The knee rig demonstrated good repeatability, with low relative variability (1.6-3.2%) in measured forces and pressures.
• Patellofemoral contact area significantly increased and shifted proximally during knee flexion (20-60 degrees).
• Mean patellofemoral contact area increased from 80.2 mm² to 349.5 mm², and pressure from 0.9 MPa to 5.9 MPa.

Conclusions:

• The developed quasi-static knee rig is a repeatable and reliable tool for biomechanical analysis of the knee.
• This rig can accurately quantify changes in patellofemoral contact area and pressure during simulated squatting.
• The findings support the use of this rig to investigate the effects of anatomical variations and surgical interventions on knee joint function.