Credit: The authors Bone-regenerating treatments are in high demand due to the ageing population. Increasingly, the orthopaedic biomaterials used to support these treatments are designed to be "immunomodulatory", i.e., guide the body's inflammatory response. They do this by encouraging macrophages - a type of white blood cell that surrounds and kills microorganisms - to adopt new roles based on signals and stimuli in their microenvironment. This approach has proved effective for developing new bone and for encouraging existing bone to accept artificial implants. Magnesium is a mineral that not only helps to maintain normal nerve and muscle function, importantly, it also supports a healthy immune system and helps bones to retain their strength. Typically, it is given to orthopaedic patients as an oral supplement.