What is bone marrow edema? Causes and treatment

Bone marrow edema, or bone marrow lesion, is a term you may have encountered in an MRI report and typically seen in traumatic injuries or in inflammatory conditions, but it can have many other causes.

MRI of knee to investigate bone marrow edema

What is bone marrow edema?

Bone marrow edema is a common finding in magnetic resonance imaging studies. The major symptom leading to the MRI is pain, but in some patients it can also be incidentally found and be asymptomatic.

Edema is a medical term that describes swelling due to the collection of fluids. In the case of bone marrow edema though, the term does not necessarily reflect its definition: this is because MRIs have different possible settings, called sequences, that result in different images of the same tissue; some of such settings are called fluid-sensitive sequences and bone marrow edema is generally seen on those so when it was first described it was thought to be a collection of fluid in the bone marrow. Later, by analyzing the tissues more carefully, they discovered that causes other than fluid collection are capable of creating an edema-like signal with an MRI. Inflammation for example increases the blood flow in the affected area, hence increasing the water content and showing the characteristic MRI signal.

For this reason, more recently the terms bone marrow lesion and bone marrow edema-like lesion are used preferentially.

How is bone marrow edema diagnosed?

Bone marrow edema is not a diagnosis, it is a sign and a finding in MRIs.

CT Scans potentially can detect bone marrow edema as well but have low sensitivity and specificity to it when compared to MRIs.

X-Rays, ultrasound and skeletal scintigraphy do not detect bone marrow edema.

How is bone marrow edema further investigated?

While diagnostic imaging exams other than the MRI can’t demonstrate bone marrow edema, they may help investigate the underlying cause and are commonly used in the differential diagnosis. Moreover, the MRI itself will provide a lot more information than just finding the edema and may help exclude several conditions.

The first step to diagnose the cause is the consult with your GP. The visit will include:

  • Asking about your symptoms.
  • Taking your medical history, to check for possible conditions causing your symptoms.
  • Physical examination to check for localized sign, such as swelling, redness, warmth, pain.
  • Checking your vital signs such as blood pressure, heart rate and body temperature.

Depending on the findings your GP may prescribe you further tests such as:

  • Complete blood count
  • Inflammatory markers, including C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR)
  • Arthrocentesis with synovial fluid analysis.
  • CT-Scan or other diagnostic imaging technique.
  • In some cases, a bone biopsy may be requested as well.

At any stage, depending on the finding and on the suspected diagnosis you may be referred to a specialist, such as an orthopedic surgeon, a rheumatologist or an oncologist.

What causes bone marrow edema?

There are many possible causes of bone marrow edema.

  1. Trauma. Commonly seen in fractures, contusions or after surgeries.
  2. Sepsis. Seen in osteomyelitis and septic arthritis.
  3. Inflammation. In arthritis, spondylitis, enthesitis.
  4. Degeneration. In osteoarthritis, tendinopathy, chondral lesions.
  5. Cancer. Both in primary and metastatic, benign or malignant bone tumors.
  6. Iatrogenic. Due to surgeries, radiotherapy, medications or other medical therapies.

Other possible causes are osteoporosis, Charcot arthropathy, and ischemia with bone necrosis.

When there is no evident cause, it is called bone marrow edema syndrome.

What types of bone marrow edema exist?

Bone marrow edema (BME) can be classified in different ways such as by cause, by body part, by location within the body part, or by type of MRI signal recorded.

While it can potentially affect any bone, it is most commonly seen in the lower limbs.

The most common types of bone marrow edema by body district are:

  • Foot BME
  • Hip BME
  • Knee BME
  • Toe BME
  • Spine BME
  • Ankle BME
  • Calcaneal BME
  • Shoulder BME

The MRI report may also contain descriptive terms that may help in narrowing down the diagnosis.

By location within a bone, the bone marrow edema can be:

  • Subchondral, when located in the part of the bone that is right under the cartilage in a joint.
  • Endplate, the flat and spongious part of the vertebra that is located between its body and the cartilage disk.
  • Periarticular, literally means around the joint; it is the part of the bone involved in the joint.
  • Subcortical. When located under the cortical (compact and hard) bone tissue.
  • Subenthesal, when located at the point of connection between a ligament or tendon and the bone.

By type of MRI signal, bone marrow edema can be

  • Focal
  • Patchy
  • Diffuse
  • Extensive
  • Reactive
  • Subtle

What is bone marrow edema syndrome?

Bone marrow edema syndrome, also known as primary BME, is a condition that has an unknown cause. It generally resolves by itself, without needing treatment, within 3-12 months. The main symptom is pain, without evidence of trauma or underlying pathologies; bone marrow edema syndrome mainly affects the hip or the knee and can usually be managed with analgesics and rest of the affected body part.

Treatment of bone marrow edema

Treatment of BME depends upon the cause of this sign. Most of the time bone marrow edema is treated conservatively. Rest, physical therapy, pain medication or anti-inflammatories may be prescribed.

Other possible treatments are:

  • Biphosphonates
  • Glucocorticoid injections
  • PRP injections

In more serious cases and as last resort, surgical core decompression with insertion of bone graft material, hydroxyapatite cement or injection of autologous bone marrow stem cells may be advised.

Recovery time

Recovery time will depend upon the underlying cause. It often resolves completely without residual symptoms within 3 to 12 months. You doctor will be able to tell you more about the recovery time based on your specific symptoms, underlying conditions and cause of bone marrow edema.

Sources

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