An extremity X-ray is a picture of your hand, wrist, arm, foot, ankle, knee, hip, or leg. It is done to see whether a bone has been fractured or a joint dislocated. It is also used to check for an injury or damage from conditions such as an infection, arthritis, bone growths (tumors), or other bone diseases, such as osteoporosis.
X-rays are a form of radiation, like light or radio waves, that are focused into a beam, much like a flashlight beam. X-rays can pass through most objects, including the human body. X-rays make a picture by striking a detector that either exposes a film or sends the picture to a computer. Dense tissues in the body, such as bones, block (absorb) many of the X-rays and look white on an X-ray picture. Less dense tissues, such as muscles and organs, block fewer of the X-rays (more of the X-rays pass through) and look like shades of gray on an X-ray. X-rays that pass only through air, such as through the lungs, look black on the picture.
Why It Is Done
Extremity X-rays are done to:
- Find the cause of pain in an extremity.
- See if your bone is fractured or your joint is dislocated.
- See if fluid has built up in the joint or around a bone.
- See if your bones are positioned properly after treatment for a fracture or dislocation, such as after placing a cast or splint on an arm or leg. An X-ray also may be done after a doctor places a device such as a pin or an artificial joint in a bone.
- Find changes in your bones caused by conditions such as an infection, arthritis, bone growths (tumors), osteoarthritis of the hip , osteoarthritis of the knee , or other bone diseases.
- Find foreign objects such as pieces of glass or metal.
- Check to see if a child's bones are growing normally.
- See if your bones and joints are in the correct position after joint replacement surgery.