Anteroposterior Radiography Demonstrates Higher Diagnostic Sensitivity for Detecting Medial Compartment Joint Space Narrowing Compared to the Rosenberg View in Knees with Anteromedial Osteoarthritis

Purpose: The most common radiographic views for diagnosing knee osteoarthritis (KOA) are full-extension anteroposterior (AP) and standing 45° flexion posteroanterior (Rosenberg) radiographs. Previous studies consistently suggest that the Rosenberg view has greater diagnostic sensitivity. However, in some patients with medial KOA, we observed that AP radiographs outperformed the Rosenberg view in detecting joint space narrowing (JSN). We hypothesized that this discrepancy could be attributed to distinct wear patterns of the medial tibial condyle. Therefore, this study aimed to evaluate the diagnostic sensitivity of AP and Rosenberg radiographs across different medial KOA wear patterns. Methods: In this prospective study, 318 patients (360 knees) who underwent total knee arthroplasty (TKA) were included. Five distinct wear patterns were assessed. Wear patterns and ligament integrity were evaluated and recorded intraoperatively. Preoperative AP and Rosenberg radiographs were analyzed to measure the medial joint space width (JSW). JSN was diagnosed based on criteria derived from JSW values. The diagnostic sensitivity for each wear pattern was calculated and compared between AP and Rosenberg views. Additionally, the frequency of intraarticular damage and medial meniscus injuries was evaluated across different wear patterns. Results: The AP view demonstrated higher diagnostic sensitivity compared to the Rosenberg view in knees with an anteromedial osteoarthritis (AMOA) wear pattern. JSW analysis revealed that the AP view showed significantly lower JSW values than the Rosenberg view in AMOA knees. Conversely, the Rosenberg view exhibited higher diagnostic sensitivity and lower JSW values in other wear patterns and across the overall patient cohort. Furthermore, patients with AMOA exhibited a greater prevalence of intact anterior cruciate ligaments (ACLs) compared to those with other wear patterns. Conclusion: Although the Rosenberg view generally provides greater diagnostic sensitivity, the AP view outperforms the Rosenberg view in detecting JSN in knees with AMOA wear patterns. This study highlights the complementary roles of AP and Rosenberg views in diagnosing JSN. Clinicians should perform both views when evaluating medial KOA. Level of Evidence: II