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 (tumours), 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 grey 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 (tumours), 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.
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 unborn 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.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form ( What is a PDF document? ).
You don't need to do anything else 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 jewellery 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 thigh bone (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 processed in case repeat pictures need to be taken. In some clinics and hospitals, X-ray pictures can be shown 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.
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. But 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 Montreal to Vancouver or 10 days in the Rocky Mountains.
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 (tumours), 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 usually has the official X-ray report ready the next day.
The bones, joints, and soft tissue look normal. No foreign objects, such as fragments of metal or glass, are present.
No infection and no abnormal growths (tumours) are present.
The joints are normal with no dislocation or signs of disease, such as arthritis.
All parts of a joint replacement are in the correct position.
Fractured bones may be present.
Foreign objects, such as fragments of metal or glass, may be present.
Abnormal growths (tumours) are present.
Signs of bleeding or infection, such as a collection of blood, pus, or gas may be present.
A joint may be dislocated.
Swelling is present in tissues around the bones even though the bones may be normal.
There are loose parts, worn parts, or an infection in a joint that has artificial pieces (joint replacement).
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- If you can't remain still during the test. This may cause the pictures to be blurry.
- If you are very overweight. This can make it hard to see details in some types of X-ray pictures.
- If you are pregnant and need an X-ray of a leg in the area close to the pelvis.
What To Think About
- Your X-ray results may be different from earlier test results because you were tested at a different medical centre or you had a different kind of test.
- 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.
- 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. To learn more, see the topic 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.
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Current as ofJune 25, 2018
Author: Healthwise Staff
Medical Review: Adam Husney, MD - Family Medicine
Brian O'Brien, MD, FRCPC - Internal Medicine
Martin J. Gabica, MD - Family Medicine
Howard B. Schaff, MD - Diagnostic Radiology