[Imaging of osteoarthritis of the peripheral joints]

Pain and loss of function are the clinical signs of osteoarthritis (OA). Conventional x-rays confirm the diagnosis or provide important hints for differential diagnosis. In the natural course of OA, x-rays are performed at longer intervals when pain increases or therapy is without effect, especially if more invasive therapies, or even surgery, becomes necessary. The advantages of x-rays are worldwide availability, cost effectiveness, very long experience with this imaging method and the possibility of storing the images for long periods of time. The typical findings of OA can be detected only roughly by quantitative methods. In many patients, grading of OA does not correlate well with the clinical symptoms. X-ray changes are part of the American College of Rheumatology (ACR) classification criteria for OA of the hand, hip and knee. Ordinary s-rays can depicting bone with a higher local resolution than any other imaging technique. Soft tissues and cartilage can be visualized only indirectly. In OA, ultrasound is the method to depict intra-articular effusion at an early stage. Osteophytes or the degree of synovitis are also visible. Concomitant changes in tendons, bursae or cartilage, such as structures in the hip, shoulder and knee, can be evaluated. MRI is an appropriate tool for describing changes in cartilage volume and concomitant soft-tissue alterations. For qualitative cartilage imaging, MRI has, to date, not been fully validated. Bone scans (bone scintigraphy) allow the differentiation of inflammatory from degenerative joint affections and may add information on the activity of the subchondral bone, which may develop to a prognostic marker of OA. This survey represents recommendations of the Commission "Imaging Techniques" of the German Rheumatology Society regarding the technical and individual conditions, indications, practical guidance and the typical findings of imaging in OA.