Symptoms such as pain and swelling can be difficult to assess in a young child. Sometimes a limp or change in gait (walking) pattern is all a parent has to go on.
X-rays are a good first look inside to see what’s going on. But unless there is a bone fracture, tumor, or hip dislocation, you’re not likely to see anything helpful.
When blood tests are negative, the next step may be additional imaging studies. The doctor has several to choose from. Ultrasound (US) is painless and noninvasive.
A special device called a sound head is moved over the skin. Sound waves pass through the soft tissues and bounce back. A picture of the soft tissues is formed and displayed up on a screen.
US can show areas or pockets of effusion (fluid collection). Abscess of the soft tissues may be evident. But this testing is not very precise. For example, it’s not always clear how much swelling is present.
If there is effusion, the physician may want to remove some of it and test it for infection caused by bacteria. This test can be painful and may be avoided in a young child. Instead, an MRI may be more useful.
Collections of fluid show up on MRI in great detail. MRI is very sensitive in picking up any problems in the bone marrow and nearby soft tissues. Such changes occur early in the course of some diseases and would not be seen otherwise.
Your pediatrician or family doctor will be able to advise you what’s the next best step. The history, physical exam, and test results so far will help point the way. An early diagnosis may be needed to prevent further problems. Don’t delay in going back to the physician for additional testing.