Objective:To explore the correlation between the level of high-mobility group box 1（HMGB-1）in synovia and serum and severity of knee osteoarthritis（KOA）. Methods:Seventy-two patients with knee osteoarthritis who underwent arthroscopic or total knee arthroplasty were selected as the experimental group and 20 patients with meniscal or ligament injury as the control group（excluding cartilage injury after arthroscopy）. The progression of osteoarthritis was classified by Kellgren-Lawrence grading scale by evaluating X-ray changes. Western Ontario and Mc Master Universities Arthritis Index（WOMAC）was used to evaluate knee function. The concentrations of HMGB-1 in serum and synovial fluid were determined by enzyme-linked immunosorbent assay（ELISA）. The levels of high-mobility group box 1（HMGB-1）in serum and synovial fluid of KOA patients were compared between the two groups and between patients with different K-L grading. Spearman rank correlation was used to analyze the correlation of the levels of HMGB-1 in serum and synovial fluid and Kellgren-Lawrence grading scale

and WOMAC score. Results:The level of HMGB1 in synovial fluid of patients with KOA was higher than that in control group（t=12.171

P=0.000）. There was no significant difference in serum HMGB1 level between patients with KOA and control group（t=0.247

P=0.620）. There was no significant correlation between synovial fluid and serum HMGB1 level in patients with KOA（r=0.021

P=0.863）. The level of HMGB1 in synovial fluid of KOA patients was positively correlated with WOMAC score and sub scores（pain score

stiffness score and functional score）

and was positively correlated with K-L grading;The level of serum HMGB1 was not significantly correlated with WOMAC score and each sub score（pain score

stiffness score and functional score）and X-ray K-L grading. Conclusion:The levels of HMGB-1 in synovial fluid of patients with KOA may be a potential biomarker for assessing the severity of KOA symptoms.