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What is Bone Marrow Edema in the Knee?

Bone marrow edema, also known as bone marrow lesion, in the knee is a condition characterized by the accumulation of fluid in the bone marrow of the knee that may result in pressure and pain within the knee. This condition is visible on an MRI, but not on regular X-ray findings.

Bone marrow is a spongy, flexible, soft tissue that is present in the middle of bones. It consists of stem cells that further differentiate into various blood cells like RBC, WBC, and platelets.

Causes of Bone Marrow Edema in Knee

Bone marrow edema is mainly caused due to the leakage of blood and fluid from the damaged capillaries surrounding the bone. This damage to the blood vessels may be caused due to various conditions that include:

  • Trauma to the knee
  • Inflammatory conditions affecting the knee joint
  • Knee ligament injury
  • Osteoarthritis of the knee
  • Bone tumors
  • Stress fractures in the knee
  • Bone infection
  • Knee tendinitis
  • Septic arthritis of the knee
  • Avascular necrosis in the knee joint
  • Osteomyelitis of the knee

Symptoms of Bone Marrow Edema in the Knee

The edema in the bones within the knee joint creates a lot of pressure and swelling which results in intense knee joint pain. Some of the other common symptoms of bone marrow edema in the knee include:

  • Swelling near the knee
  • Difficulty walking
  • Knee stiffness
  • Limited movement of the knee joint
  • Difficulty in weight-bearing
  • Recurrent knee pain and tenderness
  • Bruising of the knee

Diagnosis of Bone Marrow Edema in the Knee

Your doctor will review your medical history and symptoms and based on this a physical examination of the knee will be performed. Your doctor may also recommend the following diagnostic test:

  • Blood tests: Blood tests are performed to look for increased levels of C-reactive protein and ESR that can indicate infection or any disease.
  • Computed Tomography (CT) Scan: This scan uses multiple x-rays to produce detailed cross-sectional images of the knee joint to measure the amount of bone marrow edema.
  • Ultrasound: This test produces images of the fluid accumulation within the knee joint using sound waves of high frequency.
  • Magnetic Resonance Imaging (MRI) Scan: This is an imaging study that uses a large magnetic field and radio waves to detect any damage or swelling in the bone marrow.
  • Bone marrow biopsy: A small sample of bone marrow is taken and observed under a microscope to detect the presence of any abnormal condition.

Treatment for Bone Marrow Edema in the Knee

Treatment for bone marrow edema in the knee may vary based on the root cause and severity of the condition. This includes:

  • RICE Method: This is an acronym that stands for Rest, Ice, Compression, and Elevation of the affected knee. This is usually an effective treatment for bone marrow edema due to traumatic injury or osteonecrosis of the knee.
  • Medications: Your doctor may prescribe medications that include:
    • Prostaglandin derivatives: These medications help to increase blood circulation and promote regeneration of bone.
    • Antibiotics: These medications help to treat infection of the knee.
    • TNF-Inhibitors: These medications relieve inflammation by reducing the levels of tumor necrosis factor.
    • Anti-inflammatory drugs: Your doctor may prescribe non-steroidal anti-inflammatory drugs to reduce inflammation within the knee joint. 
  • Steroid Injections: Steroid medications will be injected into the knee joint to reduce inflammation.
  • Extracorporeal Shock-Wave Therapy (ESWT): In this procedure, a specialized probe is attached to the skin over the knee that sends shock waves into the bone marrow. This increases circulation and helps to promote healing and relieve pain.
  • Physical Therapy: Your doctor may recommend physical therapy to strengthen the knee muscles and bones.
  • Core Decompression: In this procedure, small holes are drilled into the area of bone marrow edema to relieve the pressure inside the bone. This relieves pain and allows the growth of new blood vessels that help to stimulate the growth of new bone.
  • Subchondroplasty: This is a minimally invasive procedure in which a gel material is injected into the bone marrow to provide support to the bone at the site of the edema. This material is then slowly absorbed and replaced with a healthy bone that repairs the damaged bone.
  • American Academy of Orthopaedic Surgeons
  • American Orthpaedic Society for Sports Medicine