What it means
X-rays pass easily through air and fat, and less easily through bone and other dense tissue. Where X-rays get through easily, the image looks dark. A lucency is a spot or line that is darker than the tissue around it, because something there lets more X-rays through. In bone, that may be a crack, an area of thinner bone, or a small cyst.
When it matters
What a lucency means depends on where it is. A thin dark line across a bone after an injury often means a fracture. A thin line around a joint replacement or screw can be normal. One that widens over time may mean the implant is loosening or, less often, infected. Many lucent spots inside bone are harmless, such as small cysts, but some need a closer look with CT or MRI.
Questions to ask your doctor
- Could the line be a fracture, or a normal structure such as a growth plate?
- Has the lucency changed compared with my older X-rays?
- Do I need a CT or MRI to look at it more closely?
