Diagnostic accuracy of a novel ultrasound imaging index for knee osteoarthritis: Evaluation of sensitivity, specificity, and predictive values

Purpose We aimed to develop and validate a new ultrasonography (US) index for the diagnosis of primary medial‐type knee osteoarthritis (OA). Methods In total, 156 patients (203 limbs) underwent standing knee radiography and the US for suspected knee OA. Total osteophyte height (TOH) and distance between bones (DBB) aided diagnosis. Logistic regression identified optimal cutoff values. Thresholds from logistic regression informed recipient operating characteristic curve (ROC) analysis, balancing sensitivity and specificity. These thresholds were then applied in the differential thermal analysis (DTA) to construct a 2 × 2 table. Results The TOH‐DBB index showed that a DBB of 5.6 mm or less was required to diagnose primary medial‐type knee arthropathy. The results in the 2 × 2 table were 41 true‐positive (TP), 10 false negative (FN), 22 true‐negative (TN), and 7 false positive (FP). A DBB of 5.6 mm or less and TOH of 4.7 mm or more were necessary to diagnose severe deformity. The results in the 2 × 2 table were 10 TP, 4 FN, 23 TN, and 4 FP. Conclusion The TOH‐DBB index was confirmed to capture changes in primary medial‐type knee OA across various stages.