Metal-on-metal hip surfaces and replacements are typically made from cobalt and chromium. They can functionwell for many years, but about 1% fail, producing small amounts of metal debris. This can trigger a response from the body causing erosion of bone and loosening of implants.

A number of factors can contribute to failure of these implants, including positioning of the implant and type of implant.  The Medicines and Healthcare products Regulatory Agency (MHRA) is responsible for classifying medical devices in the UK and has recalled certain implants in cases a higher than expected failure rate.

The term 'metal debris disease' is now recognised as a disease of any metal on metal modular component in the hip. The effects can be (e.g. pseudotumour formation, bone erosion, loosening of the implants, cause atrophy of the surrounding muscles) or systemic (e.g. cardiac toxicity).