Abstract
Psoriatic arthritis (PsA) is a heterogeneous inflammatory disease characterized by diverse musculoskeletal manifestations, including peripheral and axial arthritis, enthesitis, and dactylitis, often in conjunction with skin and nail psoriasis. Imaging modalities, particularly musculoskeletal ultrasound (MSUS) and magnetic resonance imaging (MRI), are crucial for accurate diagnosis, monitoring disease activity, and assessing structural damage in PsA. This review summarizes key insights from the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) 2025 session “Imaging in psoriatic arthritis: focus on axial MRI and peripheral musculoskeletal ultrasound,” highlighting advancements in both peripheral and axial imaging. Efforts to standardize imaging protocols and scoring systems continue to enhance the utility and reliability of these tools in both research and daily practice, emphasizing the importance of nuanced interpretation to avoid common pitfalls. The session also underscored the valuable input from patient research partners, whose involvement highlights a crucial commitment to patient-centered research and care in rheumatology.
Introduction
Psoriatic arthritis (PsA) is a heterogeneous inflammatory disease characterized by diverse musculoskeletal (MSK) manifestations, including peripheral and axial arthritis, enthesitis, and dactylitis, often in conjunction with skin and nail psoriasis (PsO).1,2 Early identification of inflammation is critical to improve patient outcomes and prevent irreversible structural damage.1-3 However, clinical examination alone has limited sensitivity for detecting subtle inflammation and distinguishing it from noninflammatory causes, which may contribute to diagnostic delays.2 MSK ultrasound (MSUS) and magnetic resonance imaging (MRI) have become useful and reliable tools for understanding PsA pathogenesis and refining disease assessment.2,4 This report summarizes the session “Imaging in psoriatic arthritis: focus on axial MRI and peripheral musculoskeletal ultrasound” held during the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) 2025 annual meeting in Bogotá, Colombia. The session featured expert clinical presentations by Dr. Catherine Bakewell and Dr. Manouk de Hooge, alongside the active participation and insights of patient research partners (PRPs) Arnon Katz and Wendy Wagenaar. We examine the evolving roles of imaging in evaluating peripheral and axial disease, the development of standardized scoring systems, and the importance of nuanced interpretation in clinical practice and research.
Peripheral MSUS
Bakewell (Salt Lake City, Utah, USA) highlighted the value of MSUS as a highly accessible tool for the real-time evaluation of peripheral joint and soft tissue pathologies, particularly enthesitis.5-7 The Global OMERACT Ultrasound Dactylitis Score (GLOUDAS) project focused on nonweight-dependent smaller joints to identify enthesitis.6 This project validated the feasibility of evaluating small entheses in the hands on US through cadaveric specimens, leading to the publication of the GLOUDAS US score for enthesitis at the fingers.6
The utility of US extends beyond specific scoring systems. This highlights the growing role of US. For patients with PsO presenting with MSK symptoms, MSUS can identify elementary inflammatory lesions predictive of subsequent PsA development, thereby facilitating early diagnosis.8-10 Further, integrating MSUS findings can significantly enhance the sensitivity of the Classification Criteria for Psoriatic Arthritis (CASPAR), potentially doubling the number of patients correctly classified with PsA.11 This capacity also positions US to improve the specificity of referrals from dermatology to rheumatology settings.12,13 Ongoing efforts by groups like the American College of Rheumatology and Ultrasound School of North American Rheumatologists (USSONAR) to publish formal guidance for the use of MSUS recommendations in PsA diagnosis, treatment monitoring, and assessment of remission underscore its expanding role in routine care.14
It should however be noted that MSUS should not be indiscriminately applied to every clinical scenario and issues of feasibility in routine clinical care must be accounted for.15 These guidance statements are intended for application only in cases of clinical uncertainty or other specified scenarios in which MSUS can add value alongside clinical evaluation. Although emerging technologies, such as robotic-assisted scanning and artificial intelligence–driven analysis, show promise for standardizing image acquisition—particularly for dorsal views of the hands—these tools remain investigational and are not yet ready for widespread clinical application.16,17
Patient perspective. The section integrated a live dialogue with PRPs. Katz and Wagenaar highlighted that “from a patient’s perspective, US is valued for its direct availability and immediate results, allowing for direct discussion with the doctor. However, patients frequently face issues with machine availability and variability in operator skills, which can lead to frustration and discomfort.”
Axial MRI
De Hooge (Ghent, Belgium) provided an overview of the role of MRI in the assessment of axial involvement in PsA, emphasizing its ability to detect both inflammatory and structural lesions.2,18,19 Critical aspects of axial MRI in PsA were outlined, covering the following20,21:
• What is known about axial MRI lesions in PsA. MRI consistently reveals both inflammatory and structural lesions in the sacroiliac (SI) joints and spine of patients with PsA, often irrespective of clinical symptoms such as back pain.22,23 The prevalence of MRI-confirmed axial involvement varies across studies. For instance, the STAR trial reported abnormalities in ~30% of biologic-naïve patients, with 15% showing concurrent spinal and SI joint lesions.24,25 Similarly, a Greek cohort found that among PsA patients with axial disease, MRI detected lesions in ~40% in the SI joints and 30% in the spine.26 Further, recent research indicates that MRI can identify distinct lesion patterns that help differentiate specifically axial PsA (axPsA) from other phenotypes of spondyloarthritis (SpA).22,23
• CASPAR vs Assessment of SpondyloArthritis international Society criteria containing MRI. The CASPAR criteria are established for classifying PsA, but do not incorporate MRI evaluation,27-29 whereas the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial SpA (axSpA), as well as the recently updated ASAS–Spondyloarthritis Research and Treatment Network (SPARTAN) classification criteria,30 specifically do.5,31-36 However, the ASAS definition of a positive MRI is intended for research classification rather than routine clinical diagnosis and may show poor sensitivity for sacroiliitis in PsA.20,32,37,38 Consequently, a significant proportion of patients with axPsA do not fulfill the ASAS classification criteria for axSpA, even when structural damage like syndesmophytes is present.19,39-41 However, it is currently unknown what proportion of patients with axPsA would meet the updated classification criteria, as these were introduced after the symposium.
• Types of lesions. MRI can detect both inflammatory and structural lesions in axPsA, including erosions in the SI joints/spine, fat lesions in the SI joints/spine, sclerosis in the SI joints, syndesmophytes in the spine, and ankylosis in the SI joints/spine.20,37,42-48
• ASAS definition of positive MRI of SI joints. According to the 2016 ASAS-MRI working group update on definitions,20 the presence of bone marrow edema (BME) or osteitis highly suggestive of SpA is considered the essential feature for the definition of active sacroiliitis. Although other active inflammatory lesions such as synovitis, enthesitis, or capsulitis may be detected, their presence in isolation without accompanying BME is not sufficient to define active sacroiliitis. Overdiagnosis of axPsA/axSpA may occur if interpretation relies solely on MRI abnormalities without considering the clinical context.49
• MRI assessment in daily practice vs a study setting (scoring methods). The approach to MRI assessment differs substantially between routine clinical practice and research settings. In daily practice, evaluation relies on qualitative, descriptive radiological reports rather than quantitative scoring, although initiatives like the ASAS recommendations seek to standardize reporting for clinical utility.49 Conversely, research and clinical trials mandate validated scoring systems to objectively measure severity and treatment response20,32,33,37,42-45,47,49-61 (Table).
Scoring methods for assessment of lesions on axial skeleton MRI.
The MOSAIC trial found that the Canada-Denmark (CANDEN) MRI score, compared to the Spondyloarthritis Research Consortium of Canada (SPARCC) score, more effectively detected treatment-related reductions in axial inflammation.60 However, it should be noted that the CANDEN score is more comprehensive, which may increase its responsiveness and, consequently, the probability of detecting change compared to less extensive scoring systems such as SPARCC.
Patient perspective. The PRPs shared that “regarding MRI, patients value the detailed information, which might be especially helpful for early diagnosis and treatment. However, they also highlight practical challenges such as the noisy and claustrophobic environment, the inability to undergo the scan if they have metal implants, and the potential need for anesthesia, underscoring significant barriers to access and comfort.”
Conclusion
MSUS and MRI are valuable modalities for assessing diverse peripheral and axial manifestations of PsA. International working groups like GRAPPA and ASAS are developing standardized definitions and scoring systems to improve diagnostic accuracy and the evaluation of treatment efficacy. These patient-centered efforts are critical for facilitating earlier, more targeted interventions, ultimately ensuring that advancements in managing PsA are both clinically meaningful and enhance patient outcomes.
Footnotes
C. Bakewell and M. de Hooge contributed equally as co-senior authors.
FUNDING
The authors declare no funding or support for this work.
COMPETING INTERESTS
SHU has received honoraria/consultancy fees from AbbVie, Novartis, GSK, J&J, AstraZeneca, Pfizer, Pharmalab-SteinCares, and Amgen. CB has received honoraria/consulting fees from AbbVie, J&J, UCB, BMS, Sobi, Lilly, Novartis, Pfizer, and Takeda. MdH has received honoraria/consulting fees from UCB and Adium. The remaining authors declare no conflicts of interest relevant to this article.
ETHICS AND PATIENT CONSENT
Institutional review board approval and patient consent were not required.
PEER REVIEW
As part of the supplement series GRAPPA 2025, this report was reviewed internally and approved by the Guest Editors for integrity, accuracy, and consistency with scientific and ethical standards.
- Accepted for publication April 27, 2026.
- Copyright © 2026 by the Journal of Rheumatology
This is an Open Access article, which permits use, distribution, and reproduction, without modification, provided the original article is correctly cited and is not used for commercial purposes.
