はじめに
Knee osteoarthritis (KOA) is a common, debilitating condition causing pain, reduced mobility, and often leading to total knee replacement. While surgery is effective, it is invasive, costly, and requires long recovery. Patients and clinicians increasingly seek conservative alternatives. Extracorporeal shockwave therapy (ESWT), a non-invasive treatment initially used for kidney stones, shows promise in reducing pain, improving function, and promoting tissue regeneration. A key question is whether ESWT can meaningfully delay knee replacement while preserving joint health.
Understanding Knee Osteoarthritis (KOA)
Knee osteoarthritis (KOA) is a degenerative joint disease marked by progressive cartilage breakdown, subchondral bone remodeling, osteophyte formation, and synovial inflammation. Mechanical stress, inflammatory mediators, and altered chondrocyte metabolism drive cartilage deterioration. As cartilage thins, underlying bone becomes exposed, causing friction, inflammation, and pain. The body attempts repair through osteophytes and increased synovial fluid, which often worsens symptoms. KOA progresses through stages: early-stage with minimal cartilage damage and intermittent symptoms, moderate disease with visible cartilage loss and persistent pain, and advanced disease with severe cartilage depletion and functional limitation. This gradual deterioration affects joint cushioning, mobility, and overall function.
Prevalence, Risk Factors, and Impact on Daily Life
KOA affects roughly 365 million people globally, with prevalence rising sharply after age 65. Risk factors include aging, obesity, previous knee injury, genetics, female sex (especially post-menopause), repetitive occupational strain, and biomechanical issues like malalignment or muscle weakness. Daily life is heavily impacted: walking, climbing stairs, standing, and squatting become difficult. Pain often disrupts sleep, while depression and anxiety are common. Reduced mobility limits social and recreational activities, and economic consequences include medical costs, lost productivity, and potential early retirement. KOA’s physical, psychological, and financial burdens make management a critical priority for patients and healthcare providers.
User Pain Points: Why Patients Seek Non-Surgical Options
Patients with KOA often pursue non-surgical treatments to avoid risks associated with knee replacement, including infection, blood clots, anesthesia complications, and prosthetic failure. Extended rehabilitation—3–6 months for functional recovery and up to a year for full healing—further motivates conservative options. Younger patients worry about prosthetic lifespan and potential revision surgeries. Many wish to preserve natural joint biomechanics and reduce surgical costs or time off work. Additionally, uncertainty regarding surgical outcomes, as 15–20% report dissatisfaction post-arthroplasty, drives interest in therapies that relieve symptoms, maintain mobility, and potentially delay surgery until later in life.
衝撃波治療とは？
体外衝撃波治療 (ESWT) is a non-invasive treatment that uses acoustic pressure waves to stimulate healing in musculoskeletal tissues. Originally developed for kidney stone fragmentation, it now treats orthopedic and sports injuries. Unlike continuous ultrasound, shockwaves are single high-pressure pulses followed by low-tension phases, producing mechanical effects that promote tissue repair. Modern devices generate waves via electrohydraulic, electromagnetic, or piezoelectric systems, each differing in focal depth, energy delivery, and precision, allowing targeted treatment for various musculoskeletal conditions.
Definition and Overview of Shockwave Therapy
Extracorporeal shockwave therapy (ESWT) is a non-invasive treatment that uses high-energy acoustic waves to stimulate healing in musculoskeletal tissues. By delivering focused pulses, ESWT creates mechanical stress in targeted areas, promoting tissue repair, reducing inflammation, and improving blood circulation. Treatment parameters such as energy flux density, pulse frequency, and the number of sessions are tailored to the patient’s condition and tolerance. In knee osteoarthritis, ESWT is applied to joint compartments, ligaments, and surrounding soft tissues to alleviate pain, enhance joint function, and improve mobility. Its non-invasive nature allows outpatient administration without anesthesia, making it a convenient and safe option. ESWT provides a reproducible and effective alternative or complement to conventional therapies, helping patients manage symptoms, maintain activity levels, and potentially delay the need for surgical interventions such as knee replacement.
How Shockwave Therapy Works: Mechanism of Action
The therapeutic effects of shockwave therapy for knee osteoarthritis derive from complex biological responses triggered by mechanical acoustic wave energy interacting with cellular and tissue structures. Understanding these mechanisms provides insight into why shockwave therapy may offer disease-modifying potential beyond simple symptomatic relief.
組織の再生と修復を促す
Shockwave therapy promotes cartilage regeneration by activating chondrocytes, which maintain cartilage matrix and integrity. Mechanical stress from acoustic waves triggers mechanotransduction pathways, stimulating chondrocyte proliferation and extracellular matrix synthesis, including type II collagen and proteoglycans. The therapy also induces angiogenesis in periarticular tissues, enhancing nutrient and oxygen delivery to support repair. Mesenchymal stem cells are recruited and differentiate toward chondrocyte lineages, replenishing depleted cartilage cells. Growth factors such as TGF-β, BMPs, and VEGF increase, orchestrating tissue repair cascades. These regenerative effects target underlying pathology rather than only relieving symptoms, distinguishing shockwave therapy as a potential disease-modifying intervention for cartilage preservation and joint health.
痛みと炎症を抑える
Shockwave therapy alleviates pain by modulating inflammatory pathways and sensory nerve activity. It decreases CGRP+ nerve fibers and reduces substance P, limiting pain signal transmission. Pro-inflammatory cytokines such as IL-1β, TNF-α, and IL-6 are downregulated, while anti-inflammatory mediators increase. Synovial inflammation diminishes, easing joint swelling and discomfort. Hyperstimulation of nociceptive endings triggers gate control mechanisms, further blocking pain signals. Peripheral nociceptors are desensitized, and central pain processing may be modulated, resulting in sustained analgesia. By addressing both inflammation and neural sensitization, shockwave therapy provides long-term symptom relief, enhancing patient comfort and supporting functional activity.
Enhancing Joint Function and Mobility
Shockwave therapy improves joint function by combining pain reduction, inflammation resolution, and tissue remodeling. Reduced pain enables greater participation in exercise and daily activities, while decreased joint effusion enhances range of motion. Periarticular soft tissues become more extensible as adhesions remodel, and osteophyte mechanical effects may be altered, improving biomechanics. Proprioception and neuromuscular control benefit from reduced pain inhibition. These changes support rehabilitation by strengthening muscles, improving gait, and decreasing compensatory stress on other joints. Overall, therapy promotes functional recovery, mobility, and quality of life, complementing conservative KOA management strategies.
Knee Osteoarthritis and Treatment Challenges
Managing knee osteoarthritis is challenging due to its complex, progressive nature and variability among patients. Multiple joint structures—including cartilage, subchondral bone, synovium, menisci, ligaments, and periarticular tissues—contribute to pain and dysfunction. Effective treatment must address symptom relief, preserve function, and prevent secondary complications. Because KOA is chronic and progressive, interventions often provide temporary benefit, with escalation to more intensive therapies required over time. Individual differences in disease progression and treatment response necessitate personalized management strategies.
Pathophysiology of KOA: Cartilage Degeneration and Inflammation
Knee osteoarthritis (KOA) involves mechanical, biochemical, and inflammatory processes leading to progressive joint deterioration. Cartilage breakdown occurs as enzymes like matrix metalloproteinases (MMPs) degrade collagen and proteoglycans, reducing cartilage’s biomechanical integrity. Dysfunctional chondrocytes produce inflammatory mediators instead of matrix components. Increased water content causes swelling and mechanical stress. Subchondral bone remodels, leading to sclerosis and bone marrow lesions associated with pain. Synovial inflammation perpetuates cartilage degradation through cytokines and enzymes. Osteophytes form at joint margins, restricting motion and contributing to discomfort. This multifactorial pathology explains why single-target treatments often fail to fully control disease progression, necessitating multimodal and disease-modifying approaches.
Common Symptoms: Pain, Stiffness, and Reduced Mobility
KOA significantly affects function and quality of life. Pain is the primary symptom, often described as deep, aching, or “bone-on-bone,” worsening with weight-bearing and sometimes present at rest or night. Morning stiffness under 30 minutes improves with movement but may recur after inactivity. Mobility gradually declines: squatting and kneeling become difficult, progressing to challenges with stairs and flat walking. Joint instability arises from muscle weakness, proprioceptive deficits, and structural damage. Crepitus and intermittent swelling are common. Symptoms collectively reduce daily activity, independence, and social participation, highlighting the need for effective conservative and disease-modifying interventions.
Limitations of Conventional Treatments (Medications, Physical Therapy, Injections, Surgery)
Conventional KOA treatments offer symptom relief but have notable limitations. Acetaminophen provides mild pain relief; NSAIDs are more effective but carry gastrointestinal, cardiovascular, and renal risks. Opioids risk dependence and do not halt disease progression. Topical NSAIDs have limited deep-joint efficacy. Physical therapy improves function but cannot reverse cartilage damage. Corticosteroid injections provide temporary relief but may accelerate degeneration. Hyaluronic acid shows inconsistent benefit. Arthroscopic surgery lacks strong evidence for KOA. Total knee arthroplasty is effective but invasive, with prosthetic lifespan limits, recovery challenges, and variable patient satisfaction, driving interest in non-surgical, tissue-preserving alternatives.
Benefits of Shockwave Therapy for KOA Patients
Extracorporeal shockwave therapy (ESWT) offers knee osteoarthritis patients a non-invasive, multi-mechanistic treatment with potential disease-modifying effects and a strong safety profile. Unlike medications that target single pathways or provide only symptomatic relief, ESWT simultaneously reduces pain and inflammation while promoting tissue repair and remodeling. Its brief sessions and minimal downtime make it convenient for patients seeking alternatives to injections or surgery. These advantages position shockwave therapy as a valuable addition to comprehensive KOA management strategies, supporting function, mobility, and quality of life.
Pain Reduction and Symptom Relief
Shockwave therapy effectively reduces pain in knee osteoarthritis, with both short-term and sustained benefits. Clinical trials show significant decreases in Visual Analog Scale (VAS) scores and WOMAC pain subscales. Analgesic effects often begin after 2–3 sessions, peaking 4–8 weeks post-treatment. Pain relief improves sleep, daily activity participation, and overall wellbeing. Mechanisms include neurological modulation, inflammatory reduction, and potential structural improvements, offering more comprehensive relief than single-pathway medications. Many patients reduce analgesic use, lowering side effects and costs. Pain reduction also facilitates engagement in therapeutic exercises, promoting functional capacity, preventing deconditioning, and supporting long-term joint health as part of a multimodal KOA management approach.
Improvement in Joint Mobility and Function
Shockwave therapy enhances knee function by improving range of motion, gait, and daily activity performance. Effects typically peak around 8 weeks post-treatment. Patients report easier stair climbing, rising from seated positions, walking, and participation in recreational activities. Objective measures such as WOMAC function scores, Lequesne Index, and Timed Up and Go tests demonstrate significant improvements. Functional gains result from pain reduction, decreased joint effusion, improved periarticular tissue compliance, and enhanced proprioception. These improvements support independence, reduce caregiver burden, and improve quality of life, making ESWT a valuable non-invasive therapy that complements exercise and rehabilitation programs in managing KOA and preserving joint function.
Stimulating Cartilage and Tissue Repair
Shockwave therapy may promote cartilage and tissue repair, offering potential disease-modifying effects beyond symptom relief. ESWT activates chondrocytes, enhances osteocyte activity in subchondral bone, and may stimulate limited regeneration of superficial cartilage lesions. Animal studies show improved cartilage histology, increased proteoglycan content, and better collagen organization. Clinical imaging studies, including MRI, report reduced cartilage defect severity or improved cartilage quality following treatment, though evidence remains preliminary. By potentially slowing degeneration and supporting tissue repair, ESWT represents a shift from purely symptomatic therapy toward interventions that may modify KOA progression and support long-term joint health, complementing conventional conservative management strategies.
手術に代わる非侵襲的な方法
Shockwave therapy provides a non-invasive option for patients seeking to delay or avoid knee replacement. ESWT avoids surgical risks such as infection, thromboembolism, prosthetic complications, and anesthesia-related issues. Outpatient treatment allows same-day return to activities, contrasting with prolonged rehabilitation after arthroplasty. Native joint anatomy and biomechanics are preserved, maintaining proprioception and natural function. For younger patients, ESWT may extend the period before surgery, reducing the likelihood of revision procedures. The therapy is reversible, so unsuccessful outcomes do not preclude future surgery. This makes ESWT an appealing, low-risk alternative for patients seeking conservative, joint-preserving approaches while maintaining mobility and quality of life.
Minimal Side Effects and Safety Profile
Shockwave therapy is safe for knee osteoarthritis, with few minor side effects. Common effects include transient pain, mild redness, temporary swelling, or brief symptom exacerbation, generally resolving within hours or days. Serious adverse events are rare, with no reports of infection, permanent tissue damage, or systemic complications in trials. Contraindications include pregnancy, local malignancy, infection, bleeding disorders, anticoagulant use, and pacemakers. Its favorable safety profile makes ESWT suitable for elderly patients, those with comorbidities, medication sensitivities, or contraindications to injections or surgery. The therapy offers a reliable, low-risk conservative option, complementing other non-invasive KOA treatments while providing pain relief, functional improvement, and potential disease-modifying benefits.
Can Shockwave Therapy Delay Knee Replacement?
For patients with progressive knee osteoarthritis, a key question is whether shockwave therapy can delay total knee replacement, preserving native joint function and postponing surgery. While long-term, surgery-specific studies are limited, clinical trials, functional outcome research, and mechanistic evidence suggest ESWT may extend the effectiveness of conservative management. Integrating shockwave therapy into comprehensive treatment programs—including exercise, weight management, and lifestyle modifications—can optimize outcomes. Patient selection and individualized protocols are critical for maximizing potential surgical delay and maintaining joint health.
Evidence from Long-Term Outcome Studies
Although studies specifically tracking knee replacement after shockwave therapy are limited, available long-term data are encouraging. Trials with 6–12 month follow-ups show sustained pain and function improvements, with benefits peaking around 8 weeks post-treatment. Patients achieving significant symptom relief may defer surgical consultation or delay arthroplasty, though formal analysis of surgical timing is lacking. Maintenance sessions at 6–12 month intervals can prolong benefits. Indirect evidence suggests higher functional capacity and lower pain severity correlate with reduced surgical uptake, outcomes achievable through ESWT in responsive patients, highlighting its potential to extend conservative management duration.
Patient Selection and Predictors of Success
Optimal shockwave therapy outcomes depend on patient characteristics. Evidence indicates better results in mild-to-moderate KOA (Kellgren-Lawrence II–III), though some grade IV patients benefit. Younger age, lower BMI, absence of severe malalignment, and predominantly mechanical pain predict favorable response. Commitment to complementary interventions—exercise, weight management—and realistic expectations improve long-term success. Early assessment after initial sessions identifies responders likely to benefit from full treatment versus non-responders needing alternatives. Shared decision-making incorporating these factors optimizes treatment allocation, ensuring ESWT is used effectively and avoids unnecessary interventions for patients unlikely to achieve meaningful outcomes.
Combining Shockwave Therapy with Exercise and Lifestyle Modifications
Maximal benefit and surgical delay potential occur when shockwave therapy is integrated into multimodal management. Therapeutic exercise strengthens periarticular muscles, enhances stability, and reduces joint stress. Pain and mobility improvements from ESWT facilitate participation in exercise programs. Weight management lowers knee loading, while activity modification, ergonomic adjustments, and assistive devices protect joints. Nutritional strategies emphasizing anti-inflammatory diets may support tissue health. Additional modalities like manual therapy, bracing, or taping complement ESWT. This integrative approach addresses multiple KOA pathophysiology aspects, enhances functional capacity, and can extend the duration of conservative management, potentially delaying knee replacement by years.
Case Studies Highlighting Delayed Surgery
Clinical case reports illustrate shockwave therapy’s potential to delay knee replacement. Patients with moderate-to-severe KOA scheduled for arthroplasty often achieve substantial pain relief and functional improvement after ESWT, prompting postponement of surgery. Some younger patients defer arthroplasty until older age to reduce prosthetic lifespan concerns, maintaining daily activity and comfort for months or years. While anecdotal, these cases show real-world scenarios where ESWT enables surgical delay, supporting patient-centered decision-making. Formal prospective studies are needed to quantify the therapy’s impact on surgery timing and identify which patient populations benefit most from conservative management with ESWT.
Measurable Outcomes: Pain Scores, Function Tests, Imaging Results
Shockwave therapy produces measurable improvements in pain, function, and potentially joint structure. VAS and WOMAC pain scores consistently show significant reductions exceeding minimal clinically important differences. Functional assessments—including WOMAC function, Lequesne Index, KOOS, and Timed Up and Go—demonstrate meaningful mobility gains. Imaging studies using MRI, T2 mapping, or dGEMRIC suggest potential cartilage preservation or slowed degeneration. Biomarker analyses indicate reduced cartilage catabolism or enhanced anabolism, though clinical correlations require validation. These objective measures support ESWT’s biological effects, complement patient-reported outcomes, and strengthen the evidence base for its role in managing KOA and delaying surgical intervention.
結論
衝撃波治療は以下を提供する a promising non-surgical option for patients with knee osteoarthritis seeking to delay or avoid total knee replacement. By simultaneously reducing pain, minimizing inflammation, and stimulating tissue repair, ESWT addresses multiple aspects of KOA pathophysiology. Clinical studies, systematic reviews, and case reports demonstrate meaningful improvements in pain, function, and mobility, with benefits often sustained for months and potentially extended with maintenance treatments. Integrating shockwave therapy with exercise, weight management, and lifestyle modifications enhances outcomes, strengthens periarticular musculature, and promotes joint stability. Patient selection—considering disease severity, symptom patterns, and overall health—is crucial to achieving optimal results. While definitive long-term data on surgical delay remain limited, current evidence and real-world experience suggest ESWT can prolong conservative management, preserve natural joint function, and provide patients with a safe, effective, and reversible alternative to invasive interventions, supporting informed, patient-centered decision-making.