Shoulder – Normal Red Marrow
Haematopoietically active marrow is termed red marrow and is responsible for the production of blood cells, predominantly red blood cells. It consists of 40% water, 40% fat and 20% protein. With age this marrow becomes haematopoietically inactive yellow marrow consisting of 15% water, 80% fat and 5% protein.
The difference in the fat content gives it different MR imaging characteristics as shown in the following coronal T1 and STIR images. Yellow marrow appears black, red marrow as grey/white on the STIR images. Persistence of red marrow in the humeral metaphysis and scapular neck is common giving a heterogeneous marrow pattern as shown in the following examples: