Bone marrow oedema of the knee.

Magnetic resonance (MR) imaging is a frequently performed investigation for disease of the knee. Bone marrow oedema (BME) is a common MR finding with a number of causes including trauma, tumour, infection, inflammatory arthropathies and BME syndromes. This article illustrates the range of MR appearances of BME around the knee and describes secondary signs that allow the reader to determine the cause of disease and to distinguish BME from normal marrow signal changes.