Characterization and Grading of Intra-articular Synovial Masses and Mass-like lesions by Magnetic Resonance Imaging

Alsowey, Ahmed Mohamed; Mohamed, Ethar Abdelnasser; Bessar, Awad Abdelaziz; Hamed, Nesma Adel

doi:10.21608/zumj.2025.385049.3954

Characterization and Grading of Intra-articular Synovial Masses and Mass-like lesions by Magnetic Resonance Imaging

Document Type : Original Article

Authors

¹ Radiodiagnosis Department; Faculty of medicine, Zagazig University, Zagazig, Egypt.

² Radiodiagnosis Department, Faculty of Medicine, Zagazig University, Zagazig, Egypt

³ Radiodiagnosis department, Faculty of Medicine, Zagazig University, Zagazig, Egypt

10.21608/zumj.2025.385049.3954

Abstract

Background: Intra-articular synovial masses include different varieties of lesions best evaluated with magnetic resonance imaging (MRI) due to its superior resolution. This study assesses the diagnostic performance of different MRI sequences in characterizing and grading these lesions using histopathology and arthroscopy as reference standards.

Method: Thirty-eight patients with joint symptoms underwent MRI with T1-weighted images (T1-WI), T2-weighted images (T2-WI), fat suppressed-weighted images (FS-WI), susceptibility-weighted images (SWI), contrast-enhanced T1-weighted sequences and diffusion-weighted imaging (DWI). Imaging findings were correlated with histopathology results after arthroscopy.

Results: The knee was the most commonly affected joint (57.9%). Benign lesions comprised 86.8% of cases, mainly synovial chondromatosis (21.1%) and pigmented villonodular synovitis (PVNS, 18.4%), while all malignant cases (13.2%) were synovial sarcomas. MRI results were sensitivity, specificity, and accuracy of 80%, 100 %, and 90% respectively compared to the gold standard. The mean ADC (apparent diffusion coefficient) value was significantly lower in malignant lesions (0.79 ± 0.18 × 10⁻³ mm²/s) compared to benign cases (1.59 ± 0.55 × 10⁻³ mm²/s). An ADC <1.01 × 10⁻³ mm²/s achieved 100% sensitivity and 82.8% specificity in distinguishing benign from malignant lesions. High-grade synovial sarcomas had lower mean ADC values (0.66 ± 0.05 × 10⁻³ mm²/s) than low-grade tumors (0.98 ± 0.03 × 10⁻³ mm²/s), with <0.72 × 10⁻³ mm²/s as the optimal cutoff.

Conclusion: MRI is highly effective for diagnosing intra-articular synovial lesions. Advanced techniques like DWI/ADC improve its ability to distinguish benign from malignant lesions and tumor grading.

Keywords: MR Imaging; Intraarticular synovial masses; DWI; ADC.

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