Bone densitometers are specialized X-ray devices used to measure bone density. This test is typically done to search for signs of osteoporosis and osteopenia, which are diseases that diminish the density and mineral content of bones to the point that they become more susceptible to fractures. These tests are relatively common and can be performed quickly, which helps maintain patient comfort. These tests typically measure the density of the spine and hips, which are usually noticeably affected by bone-specific diseases. Some doctors also suggest performing bone density tests on the forearm.