ABSTRACT INTRODUCTION:  Arthritis is the initial manifestation of many joint disorder. The most common causes of arthritis are crystal,trauma and infection.Synovial fluid[S.F] analysis provides an easy, noninvasive option in differentiating inflammatory from noninflammatory arthritis.OBJECTIVES:The aim of this study is to determine whether S.F Adenosine deaminase (ADA) and high sensitivity C-reactive protein (hs-CRP) can be useful in differentiating inflammatory from noninflammatory arthritis. METHODS:A total of 56 patients with knee arthritis with joint effusion who were admitted in Vinayaka Mission Kirupananda Variyar Medical College and Hospital, Salem and those who attended the orthopaedic outpatient clinic during the period of October 2011 to March 2012 have been included  in this  study.  There were 14 Rheumatoid Arthritis (RA), 7 Crystal induced arthritis, 3 Septic arthritis and 32 Osteoarthritis (OA).RESULTS:Statistically significant difference in mean synovial fluid ADA and hsCRP concentration between inflammatory 35.77±3.95 IU/L, 19.69±4.46 µg/ml and noninflammatory arthritis 12.93±2.06 IU/L, 2.77±0.91 µg/ml (p values<0.0001, 0.0001) was observed. Statistically significant difference in mean synovial fluid ADA and hsCRP concentration was observed when rheumatoid arthritis (22.98±3.21 IU/L,17.54±4.23 µg/ml), crystal induced (24.23±3.34 IU/L, 19.47±3.77 µg/ml), septic arthritis (60.1±5.31 IU/L,22.07±5.40 µg/ml) were compared with osteoarthritis (12.93±2.06 IU/L,2.77±0.91 µg/ml)CONCLUSION:Synovial fluid ADA and hsCRP helps to differentiate inflammatory from noninflammatory arthritis