Bone marrow lesions (BML) are painful changes in the subchondral bone due to repetitive microtrauma to the articular surface. BML may be the result of degenerative metabolic inflammatory trauma and neoplastic processes.  
Bone marrow lesion (BML) is a clinical finding on MRI.
- BML is found in any bone in the body.
- They may be present under various conditions.
- They were first identified in 1988 and were originally called bone marrow edema (BME) .
- The term edema is used because it is believed that the fluid in the bone marrow has increased. It was later found that the histology was not edema but a variety of different factors. As a result of these findings, the term bone marrow injury has replaced bone marrow edema.  School of Biomedical Engineering Continuing to be used in the radiology community, the two terms are used interchangeably.
Definitive histopathological studies of BML are limited. When studying BML, remodeled trabeculae, myelofibrosis, bone marrow hemorrhage, ingrowth of fibrovascular tissue, and lymphocytic infiltration have been found. 
Findings on Radiological Investigations
Typical findings of a subchondral fracture: (A) coronal T1-weighted image (B) coronal T2-weighted fat and (C) sagittal T2-weighted fat. Extensive bone marrow edema characterized by low signal intensity on T1-weighted and high signal intensity on T2-weighted magnetic resonance image (asterisks) Linear low signal intensity imaging of the subchondral region (arrow). Reprinted from: Bonadio MB Ormond Filho AG Helito CP Stump XM Demange MK. Bone marrow lesions: imaging clinical manifestations and treatment. Magnetic resonance insights. April 2017
BML can be seen on MRI. BML is seen as a hypodense (lighter) area on a T1-weighted scan and as a hyperdense (darker) area on a T2-weighted scan. They have no distinct margins and cross anatomical boundaries . A fat-suppressed T2-weighted scan is often recommended to best identify BML 
Conditions that present with BMLs
BML represents a clinical finding on MRI. To diagnose the cause of myeloid lesions, the patient’s clinical history and symptoms must be considered .
In Eriksen’s (2015) article on BML, they describe that BML is present in the following conditions :
- Fractures (acute osteoporosis and stress)
- Local transient osteoporosis
- Pressure/biomechanical changes (plantar fasciitis tendonitis/enteritis)
- Bone bruise
- Osteochondral damage (osteochondritis dissecans)
- Degenerative lesions
- Osteoarthritis (hip, knee, other)
- MODIC lesions (spine)
- Inflammatory lesions
- Inflammatory joint disease and enthesitis (rheumatoid arthritis (RA) ankylosing spondylitis psoriasis)
- systemic chronic inflammation with fibrosis
- Ischaemic lesions
- Avascular necrosis (AVN)
- Complex regional pain syndrome (Sudeks’ bone atrophy)
- Sickle cell anaemia (SCA)
- Infectious lesions
- Diabetic foot Charcot foot
- Sepsis (bone infarcts)
- Metabolic/endocrine lesions
- Hydroxyapatite deposition disease (HADD)
- Iatrogenic lesions
- Immunosuppressant (glucocorticoid cyclosporine)
- Neoplastic (and neoplastic-like) lesions
Clinical Significance of BMLS
The clinical significance of BMLS is unclear. The literature is beginning to show a potential correlation between pain and function in BML . Studies have shown that the presence of BML increases the risk of cartilage loss and the development of knee pain . X-rays appear as Osteophytes and loss of joint space are often used to diagnose osteoarthritis. Bone marrow lesions may be an early clinical manifestation of OA. It has been suggested that BMLs may be an early indicator of OA and that interventions aimed at managing BMLs may lead to Protects articular cartilage. 
Treatment of BMLs
Treatment of BML is complicated because their exact cause is not fully understood. Standard treatment regimens for BML have not been agreed upon. Treatment usually focuses more on the functional manifestations of the disease symptoms.  Many studies have looked at the effects on bone Bone marrow lesions using various modalities. Most of them show that the intervention may produce functional and symptomatic changes, but may not always affect the appearance of BML on MRI .
Surgical procedures such as core decompression have been performed in the hip joint with mixed results  . New techniques such as subchondroplasty, in which calcium phosphate bone substitutes are injected into the trabeculae, show promise, but further research is needed 
Extracorporeal shock wave therapy
ESWT has been shown to reduce the occurrence of BML in the hip and knee 
An RCT published in 2018 showed promising evidence that ESWT may be an effective management strategy to help relieve pain and improve function in patients with knee OA. 
The idea behind physical unloading is that if repetitive microtrauma causes BML, then by unloading the joint, the BML should be reversible. This has not been supported by the literature. A recent study looks at the use of crutches to potentially reduce knee burden in patients with medial tibiofemoral fractures office automation. Their findings concluded that use of canes did not reduce BML volume compared with no use of canes. 
One study looked at exercises for BML and knee OA. Their final findings concluded that exercise benefited both groups with and without BML, with no significant differences between the two groups. They did find that strength training may be more effective in reducing pain in patients with BML. This can be used to help create an individual treatment plan for the patient. Their sample size was very small and further research on this is needed. 
Both bisphosphonates and prostacyclins have been shown to be somewhat helpful in improving pain in the presence of BML. The results of various studies are conflicting and tend to show more promise in the earlier stages of the disease. To date, no consensus has been reached on its mechanism of action These drugs need more research.
BML seen on MRI due to migratory osteoporosis
BML seen on MRI due to osteochondritis dissecans lesion
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- Gobbi A, Dallo I, Frank RM, Bradsell H, Saenz I, Murrel W. A review of bone marrow lesions in the arthritic knee and description of a technique for treatment. Journal of Cartilage & Joint Preservation. 2021 Sep 1;1(3):100021.
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- Van Ginckel A, Hinman RS, Wrigley TV, Hunter DJ, Marshall CJ, Duryea J, Melo L, Simic M, Kasza J, Robbins SR, Wallis JA. Effect of cane use on bone marrow lesion volume in people with medial tibiofemoral knee osteoarthritis: randomized clinical trial. Osteoarthritis and cartilage. 2019 May 21.