Does diffusion-weighted Imaging (DWI) offer added value over Conventional Magnetic Resonance Imaging (MRI) in evaluating synovial Pathologies of the Knee? - A Prospective Observational Study of 63 patients

Background Synovial pathologies of the knee include a broad spectrum of inflammatory, infective, proliferative, and neoplastic disorders. Conventional Magnetic Resonance Imaging (MRI) is widely used for evaluation; however, it has limitations in differentiating lesions with overlapping morphological features. Diffusion-Weighted Imaging (DWI), a functional MRI technique, offers additional tissue characterization without the need for contrast administration. This study aimed to assess the added diagnostic value of DWI over conventional MRI in evaluating knee synovial pathologies. Methods This hospital-based, prospective, cross-sectional study was conducted from October 2022 to May 2024 and included 63 patients aged 18–70 years with clinically suspected knee synovial pathology. All patients underwent conventional MRI and DWI. Apparent diffusion coefficient (ADC) values were calculated by placing multiple regions of interest in areas of maximum synovial thickening. MRI findings were compared with histopathological diagnosis as the reference standard. Statistical analysis was performed using SPSS software, with kappa statistics used to assess diagnostic agreement and the Kruskal-Wallis test applied for intergroup ADC comparison. Results Inflammatory synovitis (61.9%) was the most common diagnosis, followed by tubercular synovitis (9.5%), pigmented villonodular synovitis (7.9%), synovial chondromatosis (7.9%), ganglion cysts (6.3%), hemangiomas (3.2%), and synovial sarcoma (3.2%). Diffusion restriction was observed in 81% of cases. Benign lesions such as ganglion cysts and hemangiomas showed high ADC values, while malignant lesions and pigmented villonodular synovitis demonstrated low ADC values. A statistically significant difference in ADC values among various synovial pathologies was observed (p < 0.05). The agreement between MRI and histopathology was excellent (κ = 0.836, p < 0.001). Conclusion The addition of DWI to conventional MRI significantly improves diagnostic confidence in the evaluation of knee synovial pathologies, especially in differentiating benign from malignant lesions and inflammatory from infective conditions. DWI serves as a valuable, non-contrast functional imaging tool that enhances diagnostic accuracy and supports better clinical decision-making. Trial Registration: Not applicable.