Why Can an X-Ray Be Normal When MRI Shows SAPHO Syndrome?

It can be incredibly confusing and frustrating to receive an abnormal MRI report shortly after being told your X-ray was perfectly normal. A normal X-ray does not mean your pain is imaginary, and an MRI showing bone abnormalities does not by itself prove you have SAPHO syndrome. In SAPHO, this imaging discrepancy is actually a recognized occurrence ^[1]. An X-ray can be completely normal when an MRI shows bone abnormalities because the two tests look at different aspects of the bone and are sensitive to different types of disease patterns ^[1][2].

MRI is highly sensitive to early, active edema patterns inside the bone marrow, while X-rays are better at showing established mineralized or structural changes to the bone—changes that may take months or years to develop ^[2][3].

How SAPHO Findings May Appear on Imaging

Bone disease in SAPHO syndrome does not always follow a predictable sequence, but certain imaging patterns are common:

• Active Inflammatory Patterns: SAPHO can present with osteitis (inflammation of the bone) and a bone marrow edema pattern (an appearance of increased water content inside the spongy center of the bone) ^[2]. Because the mineralized outer shell of the bone may not be altered yet, an X-ray might look completely normal despite this internal edema ^[1].
• Structural and Evolving Patterns: Over time, chronic inflammation can cause the bone to react. The bone may begin to break down in some areas (lytic lesions) and overgrow in others, becoming abnormally thick and dense (osteosclerosis or hyperostosis) ^[3][4]. These dense, structural changes are typically what become visible on an X-ray ^[3][5].

This process isn’t a universal timeline. Some patients may have areas of active inflammation occurring at the exact same time as chronic structural changes, and not every patient develops the same structural abnormalities ^[6].

Comparing Imaging Tests in SAPHO

To fully understand how SAPHO is affecting your body, doctors may rely on different types of imaging tests, though not everyone needs all of them:

• MRI (Magnetic Resonance Imaging): MRI does not use ionizing radiation and is the most sensitive tool for detecting early marrow edema, inflammation of the joint lining (synovitis), and swelling in the surrounding soft tissues ^[2][7].
• CT Scans (Computed Tomography): CT scans involve ionizing radiation but provide a highly detailed look at the physical structure of the bone ^[7]. A CT scan can reveal signs of bone erosion, hardening, and thickening better than an MRI ^[6][7]. However, CT should generally only be used if answering a specific structural question would change your medical care ^[7].
• X-Rays: X-rays are a helpful baseline test that exposes you to less radiation than a CT scan. While less sensitive than MRI for marrow edema, they are useful for spotting established structural changes or ruling out other obvious causes of pain ^[1][8].

A note on follow-up: Your doctor may monitor your progress using your symptoms, physical examination, and laboratory tests rather than relying on automatic repeat imaging, since MRI changes and physical symptoms do not always change in parallel ^[9][10].

Why Imaging Isn’t the Whole Story

While an MRI is excellent at finding an edema pattern, that finding alone is considered “nonspecific.” This means the scan shows an abnormality that may reflect inflammation, but it cannot prove SAPHO syndrome is the cause ^[11]. Infections, mechanical stress, injuries, degenerative diseases, and other types of arthritis can all cause a similar MRI appearance ^[11][12].

Because of this, an accurate diagnosis requires your clinician to fit several puzzle pieces together:

• Symptoms and Exam: Recurring chest wall pain or tenderness at the sternoclavicular joint (where the collarbone meets the breastbone) are common clues ^[13]. (Note that SAPHO can also affect the spine, jaw, or limbs, and the choice of imaging depends on where you hurt ^[6]).
• Skin History: A history of skin conditions, particularly palmoplantar pustulosis (recurrent pustules and scaling on the palms and/or soles) or severe acne, strongly supports the diagnosis ^[13][14]. Psoriasis may also be relevant. Note that these skin issues can appear before, after, or entirely independent of the bone symptoms ^[13].
• Ruling Out Alternatives: Your doctor must evaluate for other causes, including malignancy or infection ^[14][15].

When to Seek Immediate Care: Because a bone infection can completely mimic the MRI findings of SAPHO, it is critical to seek prompt medical assessment if you develop a fever, chills, rapidly worsening or focal pain, new redness, warmth, or swelling over the area, or if you feel systemically unwell.