Arthrography is a type of imaging test used to look at a joint, such as the shoulder, knee, or hip. It may be done if standard X-rays do not show the needed details of the joint structure and function. In arthrography, a long, thin needle is used to put contrast dye right into the joint and a series of X-rays is taken with the joint in various positions. X-rays use small amounts of radiation to get pictures of the inside of the body. Sometimes air is used as the contrast substance when regular contrast can not be used.