Introduction: arthritis and myositis.

In this chapter background medical information pertinent to the use of MRI and/or ultrasound in various musculoskeletal conditions is presented. Appreciation of the genetic, biochemical, histological, and immunological features of rheumatic diseases will be of benefit to the technician responsible for performing and interpreting these types of interrogations. For example, recognizing that cartilage disorder predates bone findings in osteoarthritis will help identify early versus late degenerative findings. Similarly, understanding the fibrovascular nature of rheumatoid pannus will help guide the use of more sophisticated ultrasound techniques such as power Doppler.