Fundamentals of Osteoarthritis 2026: Imaging.

OBJECTIVE: Osteoarthritis (OA) is the most frequent form of arthritis with major implications on both individual and public health care levels. The field of joint tissue imaging, particularly magnetic resonance imaging (MRI) and computed tomography (CT) with the introduction photon counting technology and weight-bearing CT, has evolved rapidly. This narrative review will provide an introduction to the different aspects of OA imaging. DESIGN: A non-systematic literature search was conducted using PubMed to identify relevant publications. The search strategy initially incorporated the title of the present manuscript and was subsequently expanded to include a comprehensive range of predefined keywords and their variants. RESULTS: Despite its known limitations, conventional radiography remains the most commonly utilized imaging modality for OA in the clinic. MRI plays a pivotal role in elucidating the natural history of OA and in guiding the development of therapeutic strategies. It can evaluate the joint as a whole organ, and provides direct, 3D assessment of cartilage morphology or composition. Ultrasound is an important adjunct in clinical practice. The roles of CT, CT arthrography, scintigraphy, and PET in the diagnosis and follow-up of OA remain limited; however, these modalities are undergoing rapid technological advancement. CONCLUSIONS: The integration of high-resolution morphological imaging with advanced compositional MRI techniques will likely expand the role of imaging in clinical practice, particularly with the anticipated development of structure- or disease-modifying therapies. Such therapies will necessitate accurate and reproducible imaging biomarkers to monitor treatment response in large patient populations. Consequently, imaging is expected to assume an increasingly central role in clinical decision-making and the management of OA.