Human knee synovial fluid cytokines correlated with grade of knee osteoarthritis--a pilot study

The purpose of this pilot study was to evaluate the cytokine profile of human knee synovial fluid and correlate this with the subject's degree of articular cartilage degradation, radiographic score, and synovial histology.

Synovial fluid was withdrawn before knee meniscectomy in 12 subjects with varying degrees of osteoarthritis and assayed for 21 cytokines, using a multiplex cytokine assay and flow cytometry instrumentation. Articular cartilage surfaces were scored by a single orthopaedic surgeon on the basis of the International Cartilage Repair Society (ICRS) classification during the arthroscopy, and posterior-anterior knee radiographs were graded using the Kellgren-Lawrence (KL) classification. Synovial biopsies were taken in four zones at the time of surgery for histological analysis.

Significant concentration differences in IL-2, IL-5, MCP-1, and MIP-1 were found between subjects with advanced arthritis and subjects with little or no arthritis on the ICRS scale (p < .05). No such differences could be appreciated using KL scores. There was no correlation between histology samples and visualized surface osteoarthritis.

This data suggests a molecular basis of disease progression, with higher levels of cytokines indicative of greater degrees of osteoarthritis. These results add pilot data that can assist investigators in conducting a comparative observational study of the levels of inflammatory cytokines with radiologic and arthroscopic assessments of osteoarthritis.