Does my child need an X-ray for knee pain, and is it safe?

When an X-ray is usually helpful

• After a fall or twist with swelling, or when the child cannot bear weight
• Pain that stays in one spot for weeks
• A limp, especially in a teenager, when the hips may also be X-rayed
• Pain at night or at rest that keeps worsening
• Suspected osteochondritis dissecans, a loose fragment or a bony problem
• A kneecap that has dislocated, to look for a small fracture

For typical growing pains, mild overuse aches or classic Osgood-Schlatter disease, an X-ray is often not needed.

How safe is it?

A knee X-ray uses a very small dose of radiation, far from the trunk and organs. It is broadly comparable to the natural background radiation everyone receives over a few days. Staff limit the area exposed and may use shielding. The principle is simple: an X-ray is done when the answer will help your child, and not just in case.

Growth plates: why children's X-rays look different

Children's bones have growth plates near the knee, which appear as dark lines on the X-ray. They are normal, but they can be mistaken for a crack by someone not used to reading children's images, and injuries can involve them. An X-ray of the other knee is occasionally taken for comparison.

When MRI or ultrasound is used instead

MRI uses no radiation and shows cartilage, meniscus, ligaments and bone bruising. It is used when a ligament or meniscus injury, osteochondritis dissecans or an unexplained problem is suspected. Young children may need to keep very still for some time, and occasionally sedation is discussed. Ultrasound is quick and useful for fluid in the hip or knee. At Aman Hospital in Doha, Dr. Gelber chooses the test after examining your child, so that each scan has a purpose.