Relation of osteopontine levels in plasma and synovial fluid of patients with knee osteoarthritis to magnetic resonance imaging findings of the knee joint

Author(s): Rasha A Abdel-Magied, Walaa F Mohammed, Gihan MA Omar, Mustafa Abdel-Kader, Aliaa M Mounir & Faten Ismail Mohamed

Objective: to detect the levels in plasma and synovial fluid osteopontine (OPN) in patients with primary osteoarthritis (OA) and their relation to progressive joint damage as detected by plain radiography, Magnetic Resonance Imaging (MRI) and its impact on both functional status and disease severity.

Design: 60 patients with primary knee OA and 60 healthy controls were included. Functional status was assessed using Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), pain was assessed using Visual Analogue Scale (VAS). Kellgren-Lawrence grading scale (KL) was used to assess radiological severity. MRI using magnetic resonance imaging osteoarthritis knee score (MOAKS score), levels of plasma and synovial fluid OPN were measured.

Results: Mean synovial fluid and plasma OPN of OA patients was 218.4 ± 37.7 and 136.67 ± 35.1. Plasma OPN was significantly higher in OA than control (p<0.0001). Significant positive correlation between serum and synovial OPN in OA patients (r=0.8, p<0.0001). Significant positive correlation between synovial fluid OPN and patients' age, disease duration, VAS, WOMAC, KL scale and parameters of MOAKS score. Significant positive correlation between plasma OPN and body mass index (BMI), VAS, WOMAC and KL scale parameters of MOAKS score. OPN level were significantly higher in grade ӀV KL than other grades. Synovial fluid OPN and bone marrow lesion (BML) score were the determining predictors for the function status (p=0.003) for both and severity (p=0.004, p<0.0001). Plasma and synovial OPN show high specificity and sensitivity in relation to BML score as parameter of activity and cartilage loss score as parameter of chronicity.

Conclusion: Plasma and synovial fluid OPN correlated with the clinical features, functional status, radiological features of Knee OA and severity MOAKS score. Synovial OPN can predict both functional impact and radiological severity in patients with knee OA.