A developed multibody knee model for unloading knee with cartilage penetration depth control

Area of Science:

• Biomechanics
• Orthopedics
• Medical Engineering

Background:

• Knee osteoarthritis (KOA) involves cartilage degradation, leading to pain from reduced bone-to-bone separation.
• Unloader knee braces aim to alleviate pain by reducing medial knee loading.
• Cartilage penetration depth, not just contact force, is a key factor in KOA pain.

Purpose of the Study:

• To develop and validate a biomechanical human knee model for analyzing knee osteoarthritis.
• To investigate the effectiveness of cartilage penetration depth control as a pain management strategy in KOA.
• To assess the impact of unloader knee braces on knee joint mechanics and bone-on-bone contact.

Main Methods:

• Development of a biomechanical knee model incorporating musculoskeletal dynamics and nonlinear discontinuous contact laws.
• Geometric expression of collision curves and algorithms for determining collision points.
• Simulation of knee joint motion and contact forces in healthy and KOA states, with and without unloading braces.

Main Results:

• Simulated maximum penetration depth in a healthy knee was 0.795 mm.
• In 75% KOA, penetration depth was 0.521 mm (0.5 mm cartilage, 0.021 mm bone).
• An 852 N unloading force reduced penetration depth to 0.45 mm, avoiding bone-bone contact.

Conclusions:

• Cartilage penetration depth is a critical parameter for managing knee osteoarthritis pain.
• The developed biomechanical model provides a computationally efficient method for analyzing knee contact problems.
• This approach supports the design and optimization of knee assistive devices, such as unloader braces.