MySpondylitisTeam

Great question! On an MRI, AS-related changes to bone marrow don't typically appear as "darkening" — instead, they show up as bright or light areas, which indicate fluid buildup known as bone marrow edema (BME).

BME happens when there's more water than fat in the bone marrow. In a healthy adult, bone marrow is roughly 50% Show Full Answer

Great question! On an MRI, AS-related changes to bone marrow don't typically appear as "darkening" — instead, they show up as bright or light areas, which indicate fluid buildup known as bone marrow edema (BME).

BME happens when there's more water than fat in the bone marrow. In a healthy adult, bone marrow is roughly 50% fat and 50% water. With AS, inflammation disrupts this balance, causing excess fluid to accumulate. On an MRI, this fluid-heavy bone marrow typically appears as bright (not dark) signals, especially on specific MRI sequences used to detect inflammation. This is actually one of the key ways doctors identify active inflammation in the sacroiliac joints and spine in people with AS.

If you're experiencing bone pain that worsens while sitting or lying down, it's worth mentioning to your doctor. They can order an MRI to check for signs of BME and adjust your treatment plan if needed.

 AI-generated responses are not a substitute for medical advice. These services are not intended to diagnose, treat, or cure any condition or disease. Always ask your doctor about specific health concerns.

Bone Marrow Edema and Ankylosing Spondylitis