Bone marrow edema in osteoarthritis of the knee joint

Abstract

The term "bone marrow edema" (BME) in MRI examination of the knee joint is used to describe areas of decreased signal intensity on T1-weighted images or increased signal intensity on T2-weighted images in the subchondral bone. BME is classified into ischemic (osteonecrosis), mechanical (trauma), and reactive (arthritis) types. In this review, the causes and differences in BME with spontaneous and secondary osteonecrosis and other characteristics of BME transitioning to a syndrome are considered. BME with injuries and bruises is usually reversible and passes after approximately 2–4 months, if accompanied by a cortical fracture, after 6–12 months. A fatigue fracture develops as a result of repeated overloading of normal bone structures, whereas fractures in zones of subchondral bone insufficiency spontaneously occur in pathologically changed bone tissues (for example, osteoporotic bones) without any trauma or overloading. Histological examination of the damaged subchondral bone in ischemic and mechanical BME revealed hemorrhages, microdestruction of bone trabeculae and vascular anomalies, and almost complete absence of direct edema in MRI-positive zones due to increased extracellular fluid content, which can be partially explained by methodological difficulties in detecting increased extracellular fluid by histopathological methods. Prostacyclin and bisphosphonate have been proposed as conservative therapies for ischemic and mechanical BME.In osteoarthritis (OA) of the knee joints, BME is considered a marker of rapid progression. Data on the influence of obesity, therapeutic exercise and diet, and the use of a cane on BME are presented. Analysis of the effectiveness of conservative therapy revealed a weakly positive response to bisphosphonates. Inhibitors of nerve growth factor (NGF) — monoclonal antibodies to nerve growth factor (like tanezumab and fulranumab) — reduced the severity of pain but led to an increase in the frequency of osteonecrosis and endoprosthesis. Two studies have shown a decrease in the intensity of BME with oral chondroitin sulfate. The attention of orthopedists is focused on subchondroplasty using calcium phosphates. Subchondral filling, which strengthens the bone and replaces the lost barrier function of cartilage, has a symptomatic effect and effectively counteracts the development of BME, although the long-term results need to be studied.