摘要Background Assessing the radiographic features of knee osteoarthritis (OA),especially joint space narrowing,is important for evaluating disease progression.The purpose of this study was to quantitatively analyze joint space narrowing by measuring 2 new variables:the average joint space width (aJSW) and the articulate angle (AA) on X-ray films,and to evaluate the relationship between the 2 variables,knee function and OA symptoms.Methods Using the web-based radiology viewer (Cedara I-ReachTM 4.1.1),we measured the 2 variables in 50 knees of 41 patients with knee OA participating in the Shanghai OA Study.We also evaluated the Kellgren-Lawrence (K-L) grade,the Western Ontario and McMaster Universities OA Index (WOMAC),and additional questionnaire in OA knees.The study was approved by the ethics committee of Shanghai Ninth People's Hospital (No.2009-28).Results The aJSW correlated with the K-L grade (r=-0.57,P ＜0.001),kneeling (r=0.29,P=0.04),sitting cross-legged on the floor (r=-0.31,P=0.03),WOMAC pain (r=-0.31,P=0.03),WOMAC disability (r=-0.35,P=0.01),pain while squatting (r=-0.37,P=0.01),and defecating in a squatting position (r=-0.39,P=0.01).The AA correlated with defecating in a squatting position (r=0.29,P=0.05),WOMAC disability (r=0.30,P=0.04) and K-L grade (r=0.44,P＝0.003).The K-L grade also correlated with pain while squatting (r=-0.40,P=0.005) and defecating in a squatting position (r=-0.34,P=0.02),WOMAC pain (r=0.30,P=0.04),and WOMAC disability (r=0.30,P=0.04).Conclusions The aJSW closely correlated with knee OA symptoms and function scores,and was more sensitive to knee OA related disabilities than K-L grade and the AA.The aJSW could be used as a new variable for knee OA evaluation.