Bone Marrow Lesions

Original Editor - User Name Top Contributors - Kim Jackson, Mandy Roscher, Lucinda hampton, Olajumoke Ogunleye and Robin Tacchetti

Introduction

Bone marrow lesions were first discovered in 1988. They were initially called Bone Marrow Edema (BME) . The term oedema was used as it was thought that there was an increase in fluid in the bone marrow. It was later found that histologically it is not oedema but rather a multitude of different factors. As a result of these findings, the term Bone Marrow Lesion (BML) has replaced bone marrow oedema. BME continues to be utilised in some circles, and the two terms can be used interchangeably.

Histopathology

There is limited research on the exact histopathology of BMLs. Remodelled trabeculae, bone marrow fibrosis, bone marrow bleeding, ingrowth of fibrovascular tissue and lymphocytic infiltrates have been found when investigating BMLs. (14)

Findings on Radiological Investigations

A BML is seen on MRI.  A BML on a T1-weighted scan is seen as a hypodense (lighter) area and on a T2-weighted scan as a hyperdense (darker) area. (PICTURE). They have no clear margins and cross anatomical boundaries. Fat suppressed T2- weighted scans are often suggested to best identify BMLs

Figure 1. Findings typical of subchondral fracture: (A) coronal T1-weighted image, (B) coronal T2-weighted fat, and (C) sagittal T2-weighted fat.

Extensive bone marrow oedema characterised by low signal intensity on T1-weighted and high signal intensity on T2-weighted magnetic resonance images

(asterisk) with linear low-signal-intensity imaging in the subchondral area (arrow).

Conditions that present with BMLs

BMLs represent a clinical finding on MRI. To diagnose the cause of the bone marrow lesion the patient's clinical history and symptoms must be taken into account (11).

In Eriksen's (2015) article on BMLs, they describe that BMLs are present in the following conditions:

Trauma

Fracture (acute, osteoporotic and stress)

Local transient osteoporosis

Altered stress/biomechanics (plantar fasciitis, tendinitis/entesitis)

Bone bruise

Osteochondral injuries (osteochondritis dissecans)

Degenerative lesions

Osteoarthritis (hip, knee, other)

MODIC lesions (spine)

Inflammatory lesions

Inflammatory arthropathies and enthesitis (rheumatoid arthritis (RA),

Ankylosing spondylitis, psoriasis)

Systemic chronic inflammation with fibrosis

Ischaemic lesions

Avascular necrosis (AVN)

Complex regional pain syndrome (Sudeks atrophy of bone)

Sickle cell anaemia (SCA)

Infectious lesions

Osteomyelitis

Diabetic foot, Charcot's foot

Sepsis (bone infarcts)

Metabolic/endocrine lesions

Hydroxyapatite deposition disease (HADD)

Gout

Iatrogenic lesions

Surgery

Radiotherapy

Immunosuppressants (glucocorticoids, cyclosporin)

Cytostatics

Neoplastic (and neoplastic-like) lesions

Clinical Significance of BMLS

The clinical significance of BMLS is not well understood. Literature is starting to show a potential correlation between BMLs, pain and function (11). Studies have shown that the presence of BMLs can increase the risk of cartilage loss as well as the development of knee pain (4).  X-ray findings such as osteophytes and loss of joint space are commonly used to diagnose osteoarthritis. Bone marrow lesions are possibly an early clinical finding of OA. It has been proposed that BMLs could potentially be an early indicator for OA and interventions targeted at managing the BMLs could result in the preservation of joint cartilage. (11)

Treatment of BMLs

Treatment of BML is complicated as their exact aetiology is not entirely understood. There is no agreement on standard treatment protocols for BMLs. Treatment is often targeted more at the condition, symptoms, functional presentation. (5) Many studies have been conducted looking at the effect on bone marrow lesions using various modalities. They have mostly shown that interventions may produce functional and symptomatic changes but may not always affect the appearance of BMLs on MRI.

Surgical

Surgical procedures, such as core decompression have been used in the hip with varying results . Newer techniques such a subchondroplasty where calcium phosphate bone substitute is injected into the trabeculae is showing promise but needs to be further researched

Extracorporeal shock wave therapy

ESWT has shown to reduce the appearance of BMLs in both the hip and knee ,12)

An RCT published in 2018 has shown promising evidence that ESWT may be an effective management strategy to help with pain relief and functional improvement in people with OA of the knee. (12)

Physical offloading

The idea behind physical offloading is that if repetitive microtrauma has caused a BML then, by offloading the joint, the BMLs should recover. This has not been supported by literature yet. A recent study looked at the use of a cane to potentially offload the knee in patients with medial tibiofemoral OA. Their findings concluded that the use of a cane did not reduce BML volumes compared to not using a cane. (1)

Exercise

A study looked at BMLs and exercise in knee OA. Their end findings concluded that exercise benefited both groups, those with BMLs and those without BMLs, and there was no significant difference between the groups. They did find that strength training may be more effective at reducing pain in patients with BMLs. This could be used to help create individuals treatment plans for patients. Their sample size was very small, and further research into this is required. (5)

Pharmaceutical

Bisphosphonates and prostacyclins have both shown to be somewhat beneficial with improvement in pain in conditions that present with BMLs. The results from various studies are conflicting and often show more promise in early disease stages. To date, there is no consensus on the mechanism of action of these drugs, and more research is needed.

Resources

• bulleted list
• x

or

1. numbered list
2. x