Background: Osteoarthritis is a painful chronic joint disease characterized by structural 
changes to the whole joint, including loss of articular cartilage, development of osteophytes, 
synovial inflammation, subchondral bone changes, meniscal damage, muscle weakness, and 
ligamentous laxity. Aim of the work: To detect osteopontine (OPN) in knee osteoarthritis. 
Methods: 60 patients diagnosed as primary knee OA fulfilling Arthritis Rheum 1986 OA 
classification criteria, And 60 healthy control were included. All patients subjected to 
through history taking and full examination, body mass index, plain x ray knees PA view to 
assess severity according to Kellgren and Laurence grading, plasma and synovial fluid OPN 
levels, and plasma OPN for control. Assessment of pain for OA patients by patient pain visual 
analogue scale (VAS) and for functional status by Western Ontario and McMaster 
Universities Osteoarthritis Index (WOMAC), ESR,CRP were done. Results: there was 
significant difference between both groups regarding plasma osteopontine (p<0.0001), OPN 
levels in OA patients in plasma and synovial fluid was correlated with each other (p <0.0001),
patient pain VAS, WOMAC score, K-L grading were correlated with plasma OPN levels with 
p value (0.001, <0.001, <0.001), and with synovial fluid OPN levels in primary OA patients 
with p value (0.008, <0.001, <0.001) respectively. ESR positively correlated with plasma 
OPN p=0.004. Conclusion: OPN is higher in OA patients more than control, and it is higher 
in synovial fluid than plasma in knee OA patients, OPN correlated with markers of systemic 
inflammation and has impact on functional status so it can be used as a diagnostic and 
prognostic factor in knee osteoarthritis.