Calcium phosphate particulates increase friction in the rat knee joint

Area of Science:

• Biomedical Engineering
• Orthopedics
• Rheumatology

Background:

• Basic calcium phosphate (BCP) particulates accumulate in osteoarthritis (OA) joints.
• BCP levels correlate with knee OA severity.
• The impact of cartilage mineralization on joint degeneration is not fully understood.

Purpose of the Study:

• To investigate the effect of BCP in synovial fluid on the coefficient of friction (COF) of rat knee joints.
• To determine if BCP particulates alter joint lubrication and biomechanics.

Main Methods:

• Post-mortem measurement of rat knee joint COF using a pendulum apparatus.
• Evaluation of three conditions: naïve, saline injection (sham), and BCP suspension injection.
• Analysis of pendulum decay using linear and combined linear/viscous damping friction models.

Main Results:

• BCP injection significantly increased knee joint COF by 17.6% compared to naïve joints (P=0.0012).
• BCP injection increased COF by 16.0% compared to saline-injected joints (P=0.0018).
• No significant difference in COF was observed between naïve and saline-injected joints.

Conclusions:

• Elevated joint friction due to BCP particulates indicates a potential role in articular surface degradation.
• BCP may contribute to the pathogenesis and progression of osteoarthritis.
• Further research is warranted to elucidate the mechanisms of BCP-induced joint damage.