Extracorpeal Shockwave Therapy in knee pain
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.
This article examined 126 patients who were diagnosed with BME, with early-to-mid stages of osteoarthritis.
2 groups were compared: those receiving ESWT and those receiving oral alendronate treatment for managing bone weakness and deformity. Both groups were asked to complete the Visual Analogue Scale for indication of pain, as well as the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) for self-reporting of functional capacity.
Those who received ESWT were given a topical analgesic, and were treated with ESWT with a penetration depth of between 0 and 150 mm and a focus diameter of 4 mm. Shockwaves were focused around (on the margins of) the knee under radiographic guidance. Each patient underwent 2 therapy sessions, 1 week apart. Both groups were advised to limit jumping or sprinting for 6 weeks, and were given mobility aids if needed.
When monitored over time, MRI findings showed greater immediate improvements in the ESWT group, but at the 12 and 18 month follow-ups, there was no statistically significant improvement in the ESWT group over the alendronate therapy group. The WOMAC and VAS scores also improved faster in those who underwent ESWT, but no significant difference was noted at the 12 month follow-up between groups.
ESWT is a relatively new modality, but it is currently trending as a pain management tool around the world. While much of the literature highlights the mechanism of healing due to ESWT, it is not well understood yet. Much more evidence is needed to be able to definitively determine if ESWT provides a healing mechanism.
This study was not blinded, and as with any treatment modality, the power of placebo should be considered. Further, incorporating functional therapy and a strengthening programme should be taken into consideration when working with arthritis and BME, and treatment should not rely solely on modalities to speed recovery.
> From: Kang et al., Medicine 97 (2018) e9796 (Epub ahead of print). All rights reserved to The Author(s). Click here for the online summary.
