The term "bone marrow edema," first used in 1988, refers to a build up of fluid (edema) in the bone marrow. Several conditions, including osteoarthritis or fracture, can cause edema. Not only is bone marrow edema characteristic of osteoarthritis, it also indicates a poor prognosis.
An increase in bone marrow edema is strongly associated with worsening cartilage. The extent of edema often increases over time as well. There appears to be a connection between bone marrow edema and subchondral cysts. Most subchondral cysts develop in areas where there already was subchondral bone marrow edema.
Significance of Bone Marrow Edema to OsteoarthritisAt one point, it was unclear if bone marrow edema was associated with worsening knee osteoarthritis. According to one study, conducted at the Veterans Administration hospital in Boston, Massachusetts, patients with bone marrow edema on an MRI were more likely to develop worsening osteoarthritis over a period of 15 to 30 months than patients without bone marrow edema.
Researchers also found that knee osteoarthritis with malalignment was associated with bone marrow edema and with worsening osteoarthritis. Bone marrow lesions predicted worsening even after researchers accounted for the malalignment.
In a cohort of study participants from yet another study, known as the Mechanical Factors in Arthritis of the Knee 2 (MAK-2) study, it was found that among patients with knee osteoarthritis, bone marrow lesions were rare in the early stages of osteoarthritis but they were predictive of cartilage loss, even after taking into account other types of bone lesions present within the same region.
Association of Bone Marrow Changes with Worsening of Knee Osteoarthritis. Summaries for Patients. Annals of Internal Medicine. Felson DT et al. September 2003. http://www.annals.org/content/139/5_Part_1/I-33.full
Within-subregion relationship between bone marrow lesions and subsequent cartilage loss in knee osteoarthritis. Arthritis Care & Research. February 2010. Kothari A. et al. http://onlinelibrary.wiley.com/doi/10.1002/acr.20068/full
Bone marrow edema aids diagnosis and prognosis. Diagnostic Imaging Europe. Vol. 26 No. 7. http://www.diagnosticimaging.com/europe/content/article/113619/1708578