Extremity X-ray

Test Overview

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 look black.

Why It Is Done

Extremity X-rays are done to:

• Find the cause of pain in an extremity.
• See whether your bone is fractured or your joint is dislocated.
• See whether fluid has built up in the joint or around a bone.
• See whether 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.
• Find changes in your bones caused by conditions such as an infection, arthritis, bone growths (tumors), or other bone diseases. See illustrations of osteoarthritis of the hip and osteoarthritis of the knee.
• Find foreign objects such as pieces of glass or metal.
• Check to see whether a child's bones are growing normally.
• See whether your bones and joints are in the correct position after joint replacement surgery.

How To Prepare

Before the X-ray test, tell your doctor if you are or might be pregnant. Pregnancy and the risk of radiation exposure to your baby (fetus) must be considered. The risk of damage from the X-rays is usually very low compared with the potential benefits of the test. If an extremity X-ray is absolutely necessary, a lead apron will be placed over your abdomen to help shield your baby from exposure to the X-rays.

You do not need to do anything before you have this test.

How It Is Done

An extremity X-ray is taken by a radiology technologist. The X-ray pictures are usually read by a doctor who specializes in interpreting X-rays (radiologist). Some other types of doctors can also review extremity X-ray pictures for common problems, such as fractures or arthritis.

You will need to remove any jewelry that may be in the way of the X-ray picture. You may need to take off some of your clothes, depending on which area is examined. You will be given a cloth or paper gown to use during the test. You may be allowed to keep on your underwear if it does not get in the way of the test.

During the X-ray test, you will sit by or be on an X-ray table with a film holder under the affected limb. The X-ray technologist will position your limb. If you have an injury, your leg or arm will be handled gently and supported when moved or repositioned. Pillows, sandbags, or other objects may be used to hold the injured limb in place while the pictures are taken. If you are wearing a brace or other device, it may need to be removed. A lead shield may be placed over your pelvic area to protect it from radiation.

Two or more pictures of the affected limb are usually taken. The test focuses on the specific area that is injured or damaged.

X-ray pictures may also be taken of joints or limbs other than those where the obvious injury has occurred, since an injury at one point may cause damage somewhere else. For example, X-rays of the thighbone (femur) may include pictures of both the knee and hip joints.

Sometimes an X-ray picture of the unaffected limb is taken so it can be compared with the affected limb. This may happen with children because their bones are still growing. In children, there is an area called a growth plate where new bone is forming. Because it can be difficult to see fractures or other changes in the growth plate, it is helpful to compare the affected limb to the unaffected limb.

An extremity X-ray usually takes about 5 to 10 minutes. You will wait about 5 minutes until the X-rays are developed in case repeat pictures need to be taken. In some clinics and hospitals, X-ray pictures can be made immediately on a computer screen (digitally).

How It Feels

You will feel no discomfort from the X-rays. The X-ray table may feel hard and the room may be cool. You may find that the positions you need to hold are uncomfortable or painful, especially if you have an injury.

Risks

There is always a slight risk of damage to cells or tissue from being exposed to any radiation, including the low levels of radiation used in this test. However, the risk of damage from the X-rays is usually very low compared with the potential benefits of the test.

For example, the radiation exposure from a chest X-ray is about equal to the natural radiation exposure received during a round-trip airline flight from Boston to Los Angeles (Montreal to Vancouver) or ten days in the Rocky Mountains (Denver, Colorado).

Results

An extremity X-ray is a picture of your hand, wrist, arm, foot, ankle, knee, or leg. It is done to see whether your bone has been fractured or your joint dislocated. It is also used to check for an injury or damage from conditions such as infection, arthritis, bone growths (tumors), or other bone diseases, such as osteoporosis. In an emergency, the doctor can see the initial results of an extremity X-ray in a few minutes. Otherwise, a radiologist has the X-ray report ready the next day.

What Affects the Test

The X-ray pictures may not be clear if you cannot remain still during the test.

What To Think About

• Sometimes your X-ray results may be different because you were tested at a different medical center or earlier test results are not available to compare to the new test findings.
• Extremity X-rays do not give a clear picture of soft tissue, such as cartilage, tendons, or ligaments. A computed tomography (CT) scan or magnetic resonance imaging (MRI) may be needed to check the condition of these soft tissues. For more information, see the medical tests CT Scan and Magnetic Resonance Imaging (MRI).
• Fractures or other bone problems are not always seen on an X-ray. In these cases, other tests such as a bone scan, CT scan, or MRI may be needed to give a clearer picture. For more information, see the medical test Bone Scan.
• Not all injuries to the arms or legs need X-rays. An X-ray may not be done if the doctor believes that the results would not change or affect the treatment and follow-up care.