The name “osteomyelitis” often makes people think of a bone infection. So it can be confusing when a child with bone pain is referred to rheumatology and the discussion turns to inflammation instead of antibiotics.
Chronic nonbacterial osteomyelitis, or CNO, is an inflammatory bone condition. CRMO—chronic recurrent multifocal osteomyelitis—describes a form with recurring inflammation at multiple sites. The terminology varies, but the central problem is inflammation in bone that is not explained by a typical bacterial infection.
The symptoms do not always point neatly to a bone
Children may have focal pain, swelling, tenderness, a limp, or difficulty with usual activities. Symptoms can come and go. The long bones, pelvis, collarbone, jaw, and spine are among the possible sites. Fever may be absent, and some inflamed areas cause little or no pain.
That does not mean every persistent ache is CNO. Infection, injury, tumors, and other disorders need consideration. A child with worsening pain, systemic illness, neurologic symptoms, or other concerning changes needs prompt clinical assessment.
Why imaging matters
A plain X-ray can be useful, but may not show early inflammation. MRI can identify changes in the bone marrow and nearby tissues. In selected patients, whole-body MRI helps show whether other sites are involved, including lesions that are not currently painful.
Spinal involvement deserves particular attention because inflammation can affect vertebral shape and stability. The team may recommend treatment or closer monitoring even when pain seems modest. Imaging should be interpreted with the clinical history; an abnormal scan alone does not establish the diagnosis.
Why some children need a biopsy and others do not
There is no single blood test for CNO. Clinicians assess the distribution of lesions, course over time, imaging appearance, laboratory findings, and possible alternatives. A biopsy can be important when a lesion is unusual or when infection or malignancy needs to be excluded. It is not automatically required in every typical presentation.
New EULAR/ACR classification criteria help researchers identify comparable groups of children with CNO. They are research criteria, not a stand-alone diagnostic test or a reason to ignore an atypical presentation. A child’s evaluation still requires clinical judgment.
How treatment is chosen
Nonsteroidal anti-inflammatory drugs are often used initially when appropriate. If disease remains active, or if the spine is involved, the team may discuss additional treatment. CARRA developed consensus treatment plans that include options such as methotrexate or sulfasalazine, TNF inhibitors, and bisphosphonates for selected patients.
Those plans were designed to standardize approaches and support comparative research. They do not establish that one option is best for every child. Disease sites, severity, associated skin or bowel disease, previous response, and treatment risks all influence the choice.
Antibiotics are not routine long-term treatment for established nonbacterial inflammation. However, a new suspected infection still needs assessment; having CNO does not prevent an infection from occurring.
Follow the child, not only the scan
Follow-up should include pain, function, school participation, examination, and imaging when indicated. Pain and MRI inflammation do not always change at the same speed. Persistent pain deserves attention even when inflammatory control improves, and improving pain does not always prove that every lesion has resolved.
Ask about safe activity, physical therapy, and school accommodations. Keep a record of affected sites and treatment response, and agree on which symptoms should prompt an earlier visit. The aim is to protect bone health while helping the child participate in everyday life.
Keep reading
- SAPHO: bone, joint, and skin symptoms
- Earlier teaching case: CRMO
- Living with autoinflammatory disease
Sources and further reading
- Zhao et al. CARRA consensus treatment plans for CNO refractory to NSAIDs or with active spinal lesions (2018)
- EULAR/ACR classification criteria for pediatric CNO (2025)
Adapted from Jonathan S. Hausmann’s presentation, “SAPHO and Related Syndromes,” with references and terminology updated for this article. Individual patient cases and slide images have not been reproduced.
This article provides general education, not a diagnosis or an individual treatment plan. Discuss personal medical decisions with your care team.