2-year-old female with pain Moderate joint effusion with apparent enhancing synovium suggestive of synovitis. A portion of this fluid extends along the medial aspect of the humeral metaphysis in between the humerus and heterotopic bone formation measuring 10 x 4 mm. No loose bodies are evident.Heterotopic bone formation is present circumferentially around the proximal humeral metaphysis with surrounding T1 hypointense and T2 hyperintense heterogeneous signal. The humeral cortex at this level is preserved. The underlying marrow at this level demonstrates increased T2 signal with appreciable enhancement, nonspecific. No soft tissue or osseous mass is evident.The biceps tendon is within the bicipital groove. Mildly enlarged axillary lymph nodes measuring up to 13 x 7 mm (series 4, image 19) may be reactive in etiology. At the elbow, there is also displacement of the posterior fat pad without joint effusion or abnormal signal.
Near circumferential heterotopic bone formation around the proximal humeral metaphysis with surrounding heterogeneous enhancement and edema type signal may represent myositis ossificans. Moderate right shoulder joint effusion with apparent enhancing synovium is suggestive of synovitis that may be related to direct extension of the aforementioned process. Follow-up radiographs in 2-4 weeks are recommended.