Pathological human synovial fluids. Viscosity and boundary lubricating properties

Area of Science:

• Rheumatology
• Orthopedics
• Biomedical Engineering

Background:

• Synovial fluid plays a crucial role in joint health and lubrication.
• Understanding its rheological properties is key to diagnosing and managing joint diseases.
• Variations in synovial fluid composition are linked to different pathological conditions.

Purpose of the Study:

• To investigate the relative viscosity and boundary lubrication properties of human synovial fluid.
• To correlate these properties with specific knee joint pathologies including rheumatoid arthritis, osteoarthritis, and torn menisci.
• To assess the relationship between synovial fluid characteristics and the degree of synovitis and cartilage degeneration.

Main Methods:

• Analysis of synovial fluid samples from 80 patients undergoing knee surgery.
• Measurement of relative viscosity at three distinct shear rates.
• Testing boundary lubrication using a coefficient of friction in a rubber/glass tribosystem.
• Evaluation of results against operative findings and disease diagnoses.

Main Results:

• Statistically significant differences in viscosity were observed between disease groups.
• Rheumatoid arthritis synovial fluid exhibited the lowest viscosity; torn meniscus fluid showed the highest.
• Synovial fluid from torn menisci demonstrated superior boundary lubrication compared to rheumatoid synovial fluid.
• Viscosity variations correlated with the degree of synovitis, and lubrication variations reflected cartilage degeneration.

Conclusions:

• Synovial fluid rheology (viscosity and lubrication) is disease-specific in knee joints.
• Torn meniscus-associated synovial fluid acts as a superior lubricant, suggesting a protective role.
• These biomechanical properties offer insights into joint disease progression and cartilage status.