[Quantitative analysis for narrowing of radiographic joint space in knee osteoarthritis]

Conventional radiography is first performed in the evaluation of knee osteoarthritis (OA). In view of diagnostic accuracy and reproducibility, joint space narrowing that is a typical feature of knee OA should be evaluated quantitatively based on the image findings, because it has been evaluating subjectively. We measured joint space widths and joint space areas on knee radiographs to analyze joint space narrowing quantitatively and investigated the usefulness in classification of the severity of knee OA. Radiographs of 35 no OA knees (normal group) and 46 OA knees (OA group) were analyzed in this study. Medial and lateral joint space width and joint space area were measured manually using ImageJ i.e., a public domain image processing program. Measured values were corrected for the physical size with the length of epicondylar line, and statistically significant differences between the normal group and OA group were investigated. The results showed that medial joint space width was significantly smaller and lateral joint space width was significantly larger in the OA group than in the normal group. Furthermore, joint space area in the OA group decreased significantly compared that in normal group. We conclude that joint space widths and joint space area are important parameters to classify the severity of knee OA.