arthroscopic intervention and has not been reported in the hip.Our objective was to report hip synovial fluid cytokine concentrations in hips with and without radiographic arthritis.Methods: Patients with Tonnis grade 2 or greater hip OA and those without hip arthritis (Tonnis grade 0) were identified from patients undergoing either hip arthroscopy or arthroplasty.Those with a history of prior surgery, inflammatory arthritis, crystalline arthropathy, or previous trauma to the involved hip were excluded.Patients completed functional questionnaires (modified Harris Hip score [HHS], Western Ontario and McMaster Universities Arthritis [WOMAC] Index, and the International Hip Outcomes Tool [IHOT]).Synovial fluid was collected at the time of portal establishment for those undergoing hip arthroscopy and prior to arthrotomy for the arthroplasty group.Analytes included FAC, interferon gamma (IFN-gamma, interleukin (IL-6), IL-1 receptor agonist (IL-RA), IL-1b, monocyte chemotactic protein 1 (MCP-1), eotaxin, macrophage inflammatory protein 1 beta (MIP-1 beta), interferon-inducible protein 10 (IP-10), platelet derived growth factor -BB (PDGF-BB), regulated upon activation normal T-cell expressed and presumably secreted (RANTES), tumor necrosis factor -alpha (TNFa), and vascular endothelial growth factor (VEGF).Variables recorded were Tonnis grade, center edge angle of Wiberg, and labrum and cartilage pathology.An a priori power analysis indicated that 14 patients in each group would yield a Power of 0.80 for detecting a difference in FAC concentration.Mann-Whitney U Test and regression analyses were used with an alpha value of 0.05 set as significant.Results: A total of 36 patients were included (18 arthroplasty, 18 hip arthroscopy).FAC was the only analyte to show a significant difference between those with and without OA (0.80 AE 0.2 vs. 1.09AE 1.4 ug/ml, p<0.001).There was no significant correlation between the analytes and any of the pre-operative functional assessment scores.FAC had significantly higher concentration in those without radiographic evidence of OA undergoing microfracture versus those with lesser chondral pathology (2.40 AE 1.6 vs. 0.77 AE 1.2 ug/ml, p ¼ 0.03).Conclusions: There was a significant difference in FAC concentration between patients with and without radiographic OA.Those undergoing microfracture had increased levels of FAC.This data suggests that FAC may be useful in predicting cartilage pathology in those patients with hip pain but without radiographic evidence of arthritis.