Bone marrow edema (BME) is the accumulation of fluid under the knee, and is often caused by trauma, microfractures, or osteoarthritis. It is a common finding on MRI, and when noted under the joint cartilage, it can be a contributing factor to changes of the joint surfaces.

The exact causes and pathology of BME are not fully understood, but the literature notes that BME can occur spontaneously, often due to altered weightbearing of the knee, and can cause severe pain flare-ups that last 6-12 months.

The interventions that are suggested for the management of BME are often pharmacological; both non-steroidal anti-inflammatory drugs as well as corticosteroids. 

Extracorpeal Shockwave Therapy (ESWT) is a modality that is thought to stimulate the neovascularisation of an area, and interrupts the pain signals form the nerve to the brain. This article retrospectively investigated the effectiveness of ESWT and the effects on pain and function.