Patients with systemic lupus erythematosus often have musculoskeletal complications [SLE]. While synovial tissue has long been thought to be the primary site of inflammation in lupus, entheses have not previously been considered potential disease targets. In order to evaluate enthesitis in people with systemic lupus and arthritis, researchers at the Medical College of Wisconsin examined the entheses included in the Madrid ultrasonographic enthesitis index [MASEI] in a case control study including 50 SLE patients and 30 healthy controls. The patellar tendon, rather than the quadriceps, was more often affected by the clinical enthesitis that was observed in 97 of 100 knees [97 percent] of patients. There were 58 abnormalities detected by US in asymptomatic right and left knees and 103 abnormalities detected via US in knees experiencing pain, edoema, and restricted motion. MSUS has high diagnostic specificity for enthesitis in SLE patients. SLE patients often have enthesitis, as seen by clinical observation and ultrasonography.