Finding the right tests…
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Finding the right tests…
X-Ray
Knee osteoarthritis frequently affects both knees at once, which is the most common reason both are X-rayed together rather than just the painful one. Comparing the two sides lets a doctor see whether wear is roughly even or clearly worse on one side. In children, the same both-sides approach is sometimes used to compare a suspected growth-plate injury against the normal knee, since a young knee's growth plate is cartilage and can hide a fracture on a single film. A third, less common reason is checking leg alignment, where the angle between both knees together shows a bowed or knock-kneed pattern more clearly than one knee alone would.
Each knee gets its own AP and lateral pair, and the two sets are read side by side rather than independently. For osteoarthritis, this means comparing joint space narrowing and bone spur formation between knees; for a child's suspected injury, it means checking whether the growth plate looks the same on both sides.
Because wear-related knee changes often develop in both joints, even if one knee hurts more, doctors frequently image both together to see the fuller pattern. Each knee is graded separately on the standard joint-space-narrowing and bone-spur scale, so the report can show, for instance, moderate change on one side and mild change on the other rather than treating the knees as a single unit.
As with other growth-plate concerns in children, a subtle fracture through a knee's growth plate can look close to normal on one X-ray. Comparing it against the uninjured knee makes small differences, like a slightly widened plate, easier to confirm.
Less often, both knees are imaged together specifically to look at the angle between them, since a bowed or knock-kneed pattern is a comparison between two knees, not something one knee's film can show on its own. Your doctor will tell you which of these reasons applies to your specific X-ray.
Knee osteoarthritis commonly affects both knees even when one is more painful, so comparing them shows the fuller pattern of wear. Your doctor still notes which knee is symptomatic when interpreting the images.
Yes, each knee is graded on its own using a standard scale for joint space narrowing and bone spurs, so the two results can differ from each other.
Comparing both knees together can show a bowed or knock-kneed pattern more clearly than a single knee film. Your doctor will explain if this is part of what they're checking.
Each knee receives its own low, carefully controlled dose, so the combined exposure is roughly double a single-knee X-ray, though still considered low overall.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
No. X-rays show bone, not the soft cartilage or ligaments in the knee, so a suspected tear in either knee would need an MRI to confirm.
Roughly double the time of a single-knee X-ray, since four images are taken instead of two, though the whole visit is still usually brief.
A normal-looking film doesn't fully rule out a growth-plate injury in a child, since these can be subtle. Your doctor may still treat it clinically or order further imaging if suspicion remains.