Myositis is an autoimmune inflammatory muscle disease which can decrease quality of life and increase mortality. Clinical presentation includes muscle weakness, changes in muscle microstructure, myosteatosis and myalgia. Current diagnosis is reliant on subjective clinical examinations, blood tests and invasive biopsies. Quantitative MRI techniques such as diffusion and fat fraction measurements are sensitive to changes within the muscle. 10 myositis patients and 16 healthy controls underwent scans of the thigh. Significant differences were found in fat fraction and diffusion measurements between myositis patients and healthy controls, implying these measures have potential as biomarkers in the diagnosis and management of myositis.