Fig. 4
Diagnostic dilemma in a 14-year-old female control patient without synovitis (a-c) and in a 13-year-old female patient (d-f) newly diagnosed with JIA based on International League of Associations for Rheumatology (ILAR) criteria [14]. While the first patient does not show any synovial contrast enhancement (category 1, c), there is mild synovial enhancement and some synovial fluid discernable in the JIA patient (category 2, f). Both patients, however, display retropatellar and parapatellar high signal on DWI b = 800 s/mm2. Some signal increase as in (a) is frequently encountered in normal knee joints, possibly due to “T2w shine-through” of small amounts of physiological joint fluid, making diagnostic differentiation of synovial signal category 1 and 2 difficult, or impossible