Lateral-to-Medial Femoral Condyle Length Ratio on Standard AP Knee Radiographs as a Predictor of Patellar Chondromalacia.

Background/Objectives: Patellar chondromalacia (PC) is a clinical condition characterized by early cartilage degeneration in the patellofemoral joint. This study aimed to investigate the relationship between the lateral-to-medial femoral condyle length ratio (LFCL/MFCL) measured on standard anteroposterior (AP) knee radiographs and the presence of PC. Methods: A retrospective analysis was conducted on patients who presented with anterior knee pain between 2020 and 2024. PC was diagnosed using magnetic resonance imaging (MRI). The LFCL/MFCL ratio was measured on plain radiographs. Additional morphological condylar parameters were evaluated on MRI. Symptom severity was assessed using the Kujala score. Statistical analyses included t-tests, correlation analysis, logistic regression, and receiver operating characteristic (ROC) curve analysis. Results: A total of 100 patients (50 with PC, 50 controls) were included. The LFCL/MFCL ratio was significantly higher in the PC group compared to controls (1.24 ± 0.19 vs. 1.08 ± 0.15, p = 0.002). A negative correlation was found between the LFCL/MFCL ratio and Kujala score (r = -0.322, p = 0.029). Other MRI-based parameters did not show statistically significant differences. In logistic regression, the LFCL/MFCL ratio was identified as an independent predictor of PC (p = 0.01). ROC analysis yielded an AUC of 0.743 (95% CI: 0.643-0.842). Conclusions: The LFCL/MFCL ratio, which can be easily measured on plain radiographs, may serve as a simple, cost-effective, and reproducible parameter to aid in the diagnosis of patellar chondromalacia. Further prospective studies with larger sample sizes are needed to validate this finding.