What causes bone marrow edema?

Causes of Bone Marrow Edema

Bone marrow edema is primarily caused by osteonecrosis, trauma, inflammation, infection, and malignancy, with MRI being the gold standard for diagnosis showing characteristic patterns that help identify the underlying etiology. 1

Primary Causes of Bone Marrow Edema

1. Osteonecrosis

• Results from compromised blood supply to bone, leading to bone cell death
• Risk factors include corticosteroid therapy, alcohol use, trauma, HIV, lymphoma/leukemia, chemotherapy, radiation therapy, Gaucher disease, and Caisson disease 2
• Often bilateral (70-80%) in nontraumatic femoral head cases 2
• Necrotic volume >30% in epiphyseal osteonecrosis predicts future articular collapse in 46-83% of cases 2

2. Trauma-Related Causes

• Stress fractures and insufficiency fractures
• Post-traumatic bone contusion
• Transient bone marrow edema syndrome (TBMES)
  • Self-limiting condition lasting 3-18 months 3
  • More common in middle-aged adults in third to fifth decades 4
  • Characterized by pain and increased interstitial fluid without definable cause 5

3. Inflammatory Conditions

• Axial spondyloarthritis and other inflammatory arthropathies
• Bone marrow edema is a key diagnostic finding in axial spondyloarthritis 2
• Deep bone marrow edema extending at least 1 cm from articular surface is more specific for axial spondyloarthritis 2

4. Infectious Causes

• Osteomyelitis
• Septic arthritis with adjacent bone involvement
• Typically shows characteristic patterns with adjacent soft tissue involvement 2

5. Diabetic Complications

• Charcot neuroarthropathy
• Often affects the midfoot, particularly at the metatarso-cuneiform and naviculo-cuneiform joints 2
• Can be difficult to distinguish from osteomyelitis in diabetic patients 2

6. Malignancy

• Primary bone tumors
• Metastatic disease
• Hematologic malignancies (multiple myeloma, leukemia, lymphoma) 6
• Infarct-associated sarcomas (rare) 2

Diagnostic Imaging

MRI Findings

• Gold standard for diagnosis with sensitivity and specificity approaching 100% 1
• Characteristic findings:
  • Decreased signal on T1-weighted images
  • Increased signal on T2-weighted and STIR sequences 6
• Different patterns help distinguish between causes:
  • Osteonecrosis: rim of high plasma flow surrounding subchondral area without flow 2
  • Transient bone marrow edema: subchondral spot of marked hyperperfusion 2
  • Infection: adjacent soft tissue involvement, possible abscess formation 2
  • Inflammatory: specific distribution patterns (e.g., sacroiliac joints in axSpA) 2

Other Imaging Modalities

• CT: Less sensitive than MRI but better for showing osseous details and articular collapse 2
• Bone scintigraphy: Lower specificity but useful for detecting multifocal involvement 2
• Dual-energy CT: Can quantify bone marrow edema as alternative to MRI 2

Clinical Correlation

The pattern, location, and associated findings of bone marrow edema help determine the underlying cause:

• Osteonecrosis: Typically affects femoral head, humeral head, knee, ankle, and shoulder 2
• Transient bone marrow edema syndrome: Self-limiting, resolves within 3-9 months 1
• Diabetic complications: Common in midfoot in Charcot arthropathy, while osteomyelitis mirrors ulceration sites (toes, metatarsal heads, calcaneus) 2
• Malignancy: May present with additional lesions or systemic symptoms 6

Common Pitfalls

• Bone marrow edema can be seen in up to 30% of healthy controls and in athletes 2
• Delayed diagnosis can lead to prolonged disease course and reduced quality of life 1
• Inadequate differentiation between causes can lead to inappropriate treatment 1
• In diabetic patients, distinguishing between Charcot arthropathy and osteomyelitis is challenging 2

Understanding the specific pattern, location, and clinical context of bone marrow edema is essential for accurate diagnosis and appropriate management of the underlying condition.