An arthrogram is a procedure where radiopaque dye or contrast is injected into the joint and plain x-rays are taken. It is done to diagnose infection or loosening.
Joint fluid can be removed and sent to the laboratory for culture. In this way, it can be determined if there are any bacteria or there is an infection in the joint.
If there is loosening of one of the components, the contrast material will penetrate the space around the component between the component and the bone.
This is a sign that the component is loose and has separated from bone. In some circumstances, an MRI may be combined with a contrast injection procedure. This is called an MR arthrogram.