Disclosure(s): No financial relationships with ineligible companies to disclose
Background/Purpose: Ultrasound (US) is an emerging, promising imaging modality offering a safe, radiation-free, and cost-effective option for diagnosing and assessing structural changes in knee osteoarthritis (KOA), potentially overcoming limitations of current gold-standard modalities such as X-ray and MRI. Despite growing interest in US capabilities, its diagnostic performance remains variable across studies, with no clear agreement on its accuracy compared to standard reference methods. This systematic review and meta-analysis aims to evaluate the diagnostic accuracy of US in detecting KOA and related parameters. Methods: We conducted a systematic review and meta-analysis following PRISMA guidelines (Fig 1). PubMed, Web of Science, and Scopus were searched from inception to April 4th 2025, for studies evaluating US diagnostic accuracy in detecting KOA. Studies were included if they provided sufficient data to construct 2×2 tables and used a valid reference standard. A meta-analysis estimated pooled sensitivity (Se), specificity (Sp), and the summary receiver operating characteristic (SROC) curve of US for diagnosing KOA and related parameters. All analyses were performed using R software 4.4.2. Results: We included 27 studies in the qualitative synthesis and 17 in the meta-analysis, encompassing 7,187 and 3,871 knee radiographs, respectively. US achieved a pooled Se of 0.94 (95% CI: 0.71–0.99) and Sp of 0.79 (95% CI: 0.48–0.94) for total KL grading (Fig. 2). For KL grade 0, Se was 0.47 (95% CI: 0.12–0.85) and Sp was 0.98 (95% CI: 0.19–1.00). For KL grade 1, Se was 0.95 (95% CI: 0.53–1.00) and Sp was 0.89 (95% CI: 0.44–0.99). For KL grade 2, Se was 0.99 (95% CI: 0.69–1.00) and Sp was 0.86 (95% CI: 0.48–0.97). For KL grade 3, Se was 0.87 (95% CI: 0.82–0.91) and Sp was 0.90 (95% CI: 0.67–0.98). For KL grade 4, Se was 0.94 (95% CI: 0.84–0.98) and Sp was 0.97 (95% CI: 0.42–1.00) (Fig. 3). For osteophyte detection, Se was 0.86 (95% CI: 0.76–0.92) and Sp was 0.76 (95% CI: 0.65–0.84). For cartilage degeneration, Se was 0.88 (95% CI: 0.71–0.95) and Sp was 0.76 (95% CI: 0.73–0.79). For medial meniscus protrusion (MMP), Se was 0.77 (95% CI: 0.56–0.90) and Sp was 0.70 (95% CI: 0.47–0.86) (Fig. 2). Conclusion: This systematic review and meta-analysis is the first to assess US diagnostic accuracy in detecting KOA and KOA-related structural changes, showing high pooled sensitivity and specificity for overall KL grading, individual KL grades, and the detection of osteophytes, cartilage degeneration, and MMP. Future research should focus on enhancing early stage KOA detection by US for more timely diagnosis and intervention, and explore the link between clinical symptoms and ultrasound findings to better understand how imaging correlates with patient reported outcomes.
