Factors affecting the appearance  



Under fluoroscopic guidance, a needle can be placed into a joint, and iodinated contrast can be injected while watching fluoroscopically to better define and outline a joint space or bursa. This is called arthrography. Without the contrast, the joint space or bursa is not visible.

After the joint has been injected, it is put through its range of motion to allow for complete filling of the joint space, as well as to assess the capsule, look for fragments or loose bodies in the joint space, and assess the cartilage and underlying bone.

Images from a left shoulder arthrogram are displayed. Dense structures, like bone, appear dark. The injected contrast is dark. Note the size of the joint space, and how far inferiorly it extends. The lower image shows the thickness of the articular cartilage. The white arrows indicate contrast in the joint space and the lucency between this contrast and the bone is the articular cartilage.