Knee osteoarthritis (OA) causes constant pain and stiffness when the protective cartilage on the ends of the bones wears down. This degeneration leads to bone-on-bone friction, chronic discomfort, inflammation, and reduced mobility. Conventional management often involves medication, physical therapy, and injections. Extracorporeal Shockwave Therapy (ESWT) has emerged as a non-invasive option under investigation for its potential to address the underlying pathology. ESWT utilizes focused acoustic waves to stimulate a biological response within the knee joint structures, offering an alternative therapeutic approach for patients seeking pain relief and improved function.
The Physical Mechanism of Shockwave Therapy
ESWT harnesses high-energy acoustic waves generated outside the body and focused to propagate through soft tissues into the affected knee joint areas. The mechanical energy initiates a process known as mechanotransduction, converting the physical stimulus into a biochemical signal at the cellular level. This stimulation triggers a cascade of healing responses within the joint’s tissues.
A primary effect is the promotion of neovascularization, which increases microcirculation in the subchondral bone and surrounding structures. Improved blood flow delivers oxygen and nutrients to the damaged area, accelerating tissue repair and regeneration. ESWT also exhibits an anti-inflammatory effect by influencing the immune response, such as shifting macrophage phenotypes from pro-inflammatory (M1) to anti-inflammatory (M2). The waves modulate nerve signals, reducing levels of pain-related neuropeptides like calcitonin gene-related peptide (CGRP) in sensory neurons.
The Clinical Procedure and Patient Experience
The ESWT procedure for knee OA is non-surgical and performed in an outpatient setting. Before treatment, a coupling gel is applied to the skin over the targeted knee area to ensure efficient acoustic wave transmission. The clinician uses a handheld applicator to deliver the shockwaves, focusing on painful areas around the joint capsule, tendons, and subchondral bone.
Patients report a sensation of rapid pulses or tapping, which may cause transient discomfort or mild pain during the session. The intensity is adjustable based on patient feedback, ensuring the sensation is tolerable. A single session lasts approximately 15 to 20 minutes. Treatment protocols commonly involve three to five sessions administered once per week, with the clinician determining specific energy levels and the number of pulses, often ranging from 1,000 to 4,000.
Expected Outcomes and Treatment Effectiveness
Clinical studies demonstrate that ESWT is an effective treatment for reducing pain and improving function in patients with knee OA. Outcomes are tracked using standardized assessment tools, such as the Visual Analog Scale (VAS) for pain and the Western Ontario and McMaster Universities Arthritis Index (WOMAC) for function. For example, patients receiving ESWT have seen mean VAS pain scores drop significantly, sometimes from a baseline of 7.5 to an average of 3.8 after 12 weeks.
Improvements are also noted in joint mobility and the knee’s range of motion. The therapeutic effects often appear superior to placebo or standard conservative management, such as physical therapy alone. Patients commonly report a reduction in disability, reflected by lower scores on the Lequesne Index, which measures functional limitation and severity. Evidence suggests that these positive effects in pain relief and physical function can persist for up to 12 months following treatment completion.
Safety Profile and Patient Suitability
ESWT is regarded as a safe intervention for knee OA, with adverse events typically minor and temporary. Common side effects are localized to the treatment area and include mild skin reddening, temporary soft tissue swelling, or minor bruising. Any discomfort experienced usually resolves within a few hours or days. ESWT is not suitable for all individuals, and several contraindications must be considered before treatment.
Contraindications
- The therapy is generally avoided in pregnant women due to safety concerns.
- It should not be applied directly over any known malignant tumors or acute infections near the treatment site.
- Patients with severe clotting disorders or those taking blood-thinning medications require careful consideration due to the risk of hematoma formation.
- Treatment is typically avoided over areas containing a pacemaker or other implanted electronic devices, or in the presence of metal implants.