Knee contact force in subjects with symmetrical OA grades: differences between OA severities

Area of Science:

• Biomechanics
• Orthopedics
• Medical Engineering

Background:

• Musculoskeletal models enable calculation of muscle and joint contact forces.
• Understanding joint loading is crucial for osteoarthritis (OA) progression insights.

Purpose of the Study:

• To estimate knee contact force (KCF) in patients with varying OA severity.
• To analyze KCF patterns using muscle and joint reaction forces.

Main Methods:

• Utilized OpenSim to derive muscle forces and joint reaction forces.
• Generated 3D, muscle-actuated, forward dynamic simulations of walking trials.
• Calculated KCF using the vector sum of forces along the femur's longitudinal axis.

Main Results:

• Moderate OA subjects showed similar KCF patterns to healthy individuals, but with lower second peaks.
• Severe OA subjects had similar initial peak KCF to healthy/moderate OA (over 4x BW).
• Severe OA subjects unloaded the joint post-peak, while others reloaded the knee in late stance.

Conclusions:

• Knee loading patterns differ significantly between OA severities.
• Reducing high load duration, not peak force, may be an OA compensatory strategy.
• Initial peak KCF reduction is unlikely a primary compensatory mechanism for OA patients.