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Wednesday, September 20, 2017

Bone Marrow lesions- not "bone marrow edema"

In 1995 in a misguided effort to increase my exercise program I developed severe groin pain that was shown to be hip adductor muscle tears by MR. The MR also demonstrated 2 area interpreted as "bone marrow edema" and the radiologist recommended I see my internist to evaluate with one concern being  possible myeloma. A normal protein electrophoresis allayed my concern and I decided to learn what bone marrow edema was all about.

The term "bone marrow edema" (BME) was introduced in 1988 in a radiology journal article which described the MRI findings in a group of patients with severe pain and osteoarthritis (OA) of the hip and knee.  Areas of  increased signal intensity on T2 weighted images were described  in  the femoral head and condyles. Followup examinations showed that the lesions were transient and described by the authors as a  "bone marrow edema- like" imaging pattern. Since then in spite of histological evidence that the pattern is not really marrow edema,that imaging pattern is often called BME or bone marrow edema

In 2000 a pathological examination of the resected bone in 16 patients with OA  who underwent total knee arthroplasy  (TKA) demonstrated that the bone in these BME area were in fact not edematous at all but showed varying degrees  mainly normal bone and degrees of fibrosis,necrosis,bleeding and abnormal trabeculae. The BE areas demonstrated no more edema than surrounding bone.

The term "bone marrow lesions" ( BML) is now preferable to the pathologically incorrect BME, though BME is still frequently found on MR reports.
It is now recognized that patients with knee osteoarthritis (OA) frequently have these lesions in the femoral condyles and are often but not always associated with exacerbations of pain and that these lesions may be transient and may increase or decrease in size over time  and the literature is conflicting regarding how well these BML correlate with the pain. Yet the association with pain is sufficiently strong to apparent warrant various strategies to treat BME. It seems from my sampling of  web activity that OA patients  regularly are searching for some effective treatment for BME and different operative and non operative approaches have been tried with there being no strong evidence that any approach is very effective.

BML are seen in a variety of settings.

1) Athletes in certain setting have been shown to have BMLs. For example about a third of college basketball players during their active season reported in one paper had lesions in the knee that were asymptomatic and not associated with an other findings on the MRIs. In another study 3/22 marathon runners were shown to have BMLs in the femur after a marathon.

2) trauma

3)Spontaneous osteonecrosis (ON) of the knee (SONK or SPONK)

First described by Ahlbach in 1968 the currently popular etiopathophysiology concept is that the entity is really a subchondral insufficiency fracture (SCIF).The SCIF is thought to sometimes heals  in some cases while in others is  progressive  wherein  there is  bone necrosis and subsequent impaction of subchondral bone and deleterious change in the contour of the articular surface which facilitates the progression of osteoarthritis.

4) post knee procedure ON. The typical case is a older age female with a medial  meniscus tear involving the posterior horn who undergoes an arthroscopy and a partial meniscectomy with or without a chondroplasty on an area of cartilage loss on the medial femoral condyle.

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