For many years, viscosity has been the primary method used by researchers in rheumatology to assess the physiochemical properties of synovial fluid in both normal and osteoarthritic patients. However, progress has been limited by the lack of methods that provide multiple layers of information, use small sample volumes, and are rapid. In this blinded study, Raman spectroscopy was used to assess the biochemical composition of synovial fluid collected from forty patients with clinical evidence of knee osteoarthritis at the time of elective surgical treatment. Severity of knee osteoarthritis was assessed by a radiologist using Kellgren/Lawrence (K/L) scores from knee joint x-rays, while light microscopy and Raman spectroscopy were used to examine synovial fluid aspirates (2–10 µL), deposited on fused silica slides. We show that Raman bands used to describe protein secondary structure and content can be used to detect changes in synovial fluid from osteoarthritic patients. Several Raman band intensity ratios increased significantly in spectra collected from synovial fluid in patients with radiological evidence of osteoarthritis damage. These ratios can be used to provide a “yes/no” damage assessment. Additionally, two ratios increased with K/L score and showed moderate correlative trends. These studies provide evidence that Raman spectroscopy would be a suitable candidate in the evaluation of joint damage in knee osteoarthritis patients.

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