Ozone Therapy as a Redox-Modulating Strategy in Degenerative Musculoskeletal Diseases: A Clinical-Mechanistic Review

1. Introduction

Degenerative musculoskeletal diseases, including intervertebral disc degeneration and osteoarthritis, are among the leading causes of chronic pain, disability, and reduced quality of life worldwide. Traditionally interpreted as the inevitable consequence of mechanical overload and aging, these conditions are now increasingly recognized as biologically active disorders characterized by progressive alterations in cellular functions and metabolic homeostasis rather than purely structural wear [1,2].Accumulating experimental and clinical evidence indicates that chronic oxidative stress caused by increasing amount of reactive oxygen species (ROS), in combination with mitochondrial dysfunction and persistent low-grade inflammation, plays a central role in the pathogenesis and progression of musculoskeletal degeneration. In fact, it has been reported that in cartilage, intervertebral discs, and periarticular tissues, sustained redox imbalance contributes to extracellular matrix degradation, impaired anabolic signaling, cellular senescence, and reduced tissue repair capacity. These processes promote structural deterioration and symptom persistence, particularly in chronic and recurrent disease courses[3,4]. Importantly, ROS are no longer viewed solely as cytotoxic by-products of metabolism: at physiological concentrations, they act as intracellular signaling molecules regulating redox-sensitive transcription factors and adaptive pathways involved in cellular defence, energy metabolism, and inflammatory control. Thus, disease progression appears to reflect not only cumulative oxidative damage, but also failure of endogenous redox-regulatory mechanisms that normally restore tissue homeostasis.[5]

Based on these evidence, in chronic oxidative stress diseases, therapeutic strategies aimed at restoring redox balance through activation of endogenous adaptive responses have gained increasing interest. This concept differs fundamentally from conventional approaches focused on suppressing inflammation or administering exogenous antioxidants, which may not adequately address impaired redox signaling and, in some contexts, may interfere with physiological adaptive processes. [6,7] As a consequence of these changes in therapeutic perspectives of chronic oxidative pathologies, the use of ozone in medicine has been proposed as a conservative intervention able to modulate redox homeostasis through a controlled and transient oxidative stimulus. According to several experimental works, ozone as therapeutic agent, when administered at low and calculated doses, rapidly reacts with biological substrates, generating intracellular secondary messengers able to activate cytoprotective and antioxidant pathways. However, despite growing empirical use in chronic diseases including musculoskeletal disorders, the role of ozone therapy remains controversial due to heterogeneity in treatment protocols, study designs, and outcome measures.[8]

The present clinical review examines the biological rationale for ozone therapy within the context of redox biology and summarizes current experimental and clinical evidence regarding its application in degenerative musculoskeletal diseases. By adopting a disease-oriented and mechanistic perspective, this review aims to clarify potential clinical indications, highlight methodological limitations, and identify priorities for future research.

2. Methods: Literature Search and Study Selection

A comprehensive literature review was conducted to identify experimental and clinical studies addressing oxidative stress, redox signaling, and the biological rationale and clinical applications of medical ozone therapy in degenerative musculoskeletal diseases. The review aimed to provide a critical and up-to-date synthesis of available evidence while accounting for heterogeneity in study design, interventions, and outcomes.

Electronic searches were performed in PubMed/MEDLINE, Scopus, and Google Scholar using a combination of Medical Subject Headings (MeSH) terms and free-text keywords, including “ozone therapy,” “medical ozone,” “oxidative stress,” “redox signaling,” “hormesis,” “musculoskeletal degeneration,” “osteoarthritis,” “intervertebral disc disease,” “tendinopathy,” and “low back pain.” Boolean operators (AND/OR) were applied as appropriate. The search covered publications from January 2000 to March 2025, with preference given to recent and methodologically robust studies.

Although the literature search encompassed studies published between January 2000 and March 2025 in order to capture the full evolution of redox biology and ozone-related mechanistic concepts, randomized and controlled clinical trials included in the qualitative synthesis were intentionally restricted to publications from 2020 onward. This temporal restriction was applied to ensure greater methodological homogeneity, consistency in diagnostic criteria, ozone generation technologies, dosing protocols, and outcome assessment tools. Earlier clinical studies, while historically relevant, frequently employed heterogeneous protocols and non-standardized outcome measures that limited direct comparability with more recent trials. Therefore, controlled and randomized trials published between 2020 and 2026 were prioritized for the clinical evidence synthesis, whereas older studies were considered primarily for background and mechanistic contextualization.

Eligible articles included basic science investigations, preclinical models, randomized and non-randomized clinical trials, observational studies, and relevant systematic reviews. Case reports, conference abstracts without full text, and studies lacking adequate methodological detail were excluded. Only articles published in English were considered.

Study selection was performed through title and abstract screening followed by full-text assessment for relevance to the objectives of the review. Data extraction focused on study design, patient population, musculoskeletal condition, ozone administration route and dosage, comparator interventions, and reported clinical or biological outcomes. Owing to heterogeneity across studies, no formal meta-analysis was performed. Evidence was synthesized qualitatively, with emphasis on biological plausibility, consistency of findings, and methodological limitations, and is presented thematically by mechanistic and clinical domains.[9,10]

2.1. Redox Biology of Musculoskeletal Degeneration

Degenerative musculoskeletal disorders are increasingly understood as conditions characterized by dysregulated cellular homeostasis rather than purely mechanical tissue failure. Experimental evidences showed that altered inflammatory and redox signaling has been linked to dysregulation of mechanobiological responses in musculoskeletal tissues. In fact, cells residing in cartilage, intervertebral disc, and tendon structures need of finely tuned redox-sensitive pathways to translate mechanical loading into anabolic or reparative signals. Chronic oxidative imbalance disrupts these pathways, leading to impaired mechanotransduction and reduced capacity to adapt to physiological stress, thereby accelerating degenerative changes even in the absence of overt injury.[11]

Systemic factors further contribute to redox dysregulation in degenerative musculoskeletal diseases. Metabolic disorders, vascular insufficiency, and age-related decline in antioxidant capacity may amplify local oxidative stress, creating a permissive environment for tissue degeneration. This systemic–local interaction helps explain the multifocal and progressive nature of musculoskeletal degeneration and supports the concept of redox imbalance as a shared pathogenic mechanism across different anatomical sites rather than a tissue-specific phenomenon.[12]

According to the recent evidences in redox biology, in human cells ROS are continuously generated as by-products of aerobic metabolism but their concentration is tightly regulated by enzymatic and non-enzymatic antioxidant systems, and this controlled redox environment allows ROS to function as signaling molecules involved in cell survival, energy metabolism, and tissue adaptation.[13]In degenerative musculoskeletal diseases, however, sustained inflammatory stimuli, mechanical overload, and age-related mitochondrial dysfunction disrupt this balance, leading to excessive or poorly regulated oxidant production.

Consequently, in cartilage and intervertebral disc tissues, chronic redox imbalance promotes degradation of extracellular matrix components, suppression of anabolic pathways, and activation of catabolic enzymes such as matrix metalloproteinases. Thus, it has been reported that in the pathophysiological process of the musculoskeletal degeneration, oxidative stress contributes to cellular senescence, apoptosis, and reduced proliferative capacity of chondrocytes and disc cells, ultimately impairing tissue repair and regeneration. Similar mechanisms have been described in tendinopathies, where oxidative stress interferes with collagen production and tenocyte function.[14,15]

Importantly, disease progression appears to reflect not only cumulative oxidative damage, but also failure of adaptive redox-regulatory mechanisms. At this purpose, studies reported that impaired activation of redox-sensitive transcription factors has been associated with reduced cellular resilience and heightened vulnerability to chronic stressors in musculoskeletal tissues, and increasing number of evidence support the pivotal role of the Nuclear releasing factor 2 (Nrf 2) in coordinating antioxidant defences, mitochondrial biogenesis, and cytoprotective responses.[16,17]

These observations have important therapeutic implications. Interventions aimed exclusively at scavenging free radicals or suppressing inflammation may not adequately restore physiological redox signaling and, in some contexts, may blunt endogenous adaptive responses. Consequently, there is increasing interest in conservative strategies able to modulate redox homeostasis by promoting controlled activation of cytoprotective pathways, thereby enhancing tissue resilience and functional recovery rather than simply inhibiting oxidative or inflammatory processes. The next paragraphs will elucidate the mechanism of action and the clinical application of the ozone in the treatment of musculoskeletal diseases.

2.2. Biochemical Mechanisms of Action of Ozone Therapy

2.2.1. Pharmacological Actions of Medical Ozone

Ozone (O3) is a triatomic oxygen molecule usually administered in musculoskeletal diseases as oxygen-ozone gas mixture. Due to its high reactivity as oxidant, ozone does not persist as a stable compound in biological systems and after the contact with human fluids it rapidly reacts with water-soluble antioxidants and polyunsaturated fatty acids, generating a series of secondary oxidative mediators that are responsible for therapeutic effects.[18,19,20]

Two principal classes of mediators are generated following the tissues exposure to ozone: reactive oxygen species (ROS), primarily hydrogen peroxide, and lipid oxidation products (LOPs), including aldehydes and hydroxyalkenals. Hydrogen peroxide acts as a short-lived intracellular signaling molecule capable of diffusing across cell membranes and modulating redox-sensitive pathways. In contrast, LOPs exhibit longer half-lives and can mainly exert systemic effects by interacting with cellular receptors and transcriptional regulators.

At low concentrations, ozone-derived ROS and LOPs are able to stimulate adaptive cytoprotective mechanisms rather than inducing irreversible oxidative injury. These mechanisms of action are largely related to the intracellular activation of redox-sensitive transcription factors, particularly nuclear factor erythroid 2-related factor 2 (Nrf2). In cytoplasma, oxidative modification of cysteine residues on Kelch-like ECH-associated protein 1 (Keap1) promotes Nrf2 dissociation and nuclear translocation, leading to transcription of a number of genes involved in antioxidant defense, detoxification processes, and maintenance of cellular redox balance. Upregulated gene products include enzymes regulating glutathione synthesis and recycling, thioredoxin systems, nicotinamide adenine dinucleotide phosphate (NADPH) regeneration, and heme oxygenase activity. Collectively, these pathways contribute to enhanced cellular resilience, improved mitochondrial function, and modulation of inflammatory signaling cascades. Importantly, this response to ozone-derived ROS and LOPs messengers is transient and dose-dependent, underscoring the importance of calculated ozone concentration and administration protocols.[21]

Beyond Nrf2 activation, ozone-derived mediators have been also shown to influence additional redox-sensitive pathways involved in inflammation and cellular metabolism. Experimental data suggest modulation of nuclear factor kappa B (NF-κB) signaling, with downstream effects on pro-inflammatory cytokine expression and a modulation of the immune cells function. In parallel, transient oxidative signaling may influence mitochondrial dynamics, promoting biogenesis and improving oxidative efficiency, thereby reducing baseline reactive oxygen species generation over time.[8]

Moreover, it is important to highlight that the biological response to ozone exposure appears to be context-dependent, influenced by baseline redox status, tissue oxygenation, and inflammatory burden. Consequently, cells with impaired adaptive capacity may exhibit exaggerated responses to oxidative stimuli, whereas tissues with preserved redox flexibility may respond with enhanced cytoprotective activation. This variability emphasizes the importance of individualized treatment protocols and careful patient selection, particularly in degenerative musculoskeletal conditions characterized by heterogeneous disease phenotypes.

Based on all the previous consideration, ozone therapy should therefore not be interpreted as an exogenous antioxidant treatment or a direct anti-inflammatory intervention. Instead, its proposed mechanism relies on the induction of a transient and controlled oxidative challenge able to stimulate endogenous adaptive responses. This distinction is critical for understanding both the potential therapeutic effects and the risks associated with inappropriate dosing or non-standardized application in musculoskeletal disorders.

2.2.2. Hormesis and Therapeutic Redox Modulation

The therapeutic effects attributed to the ozone should be interpreted according to the concept of hormesis, a dose–response phenomenon in which low-intensity stressors elicit adaptive and protective cellular responses, whereas excessive exposure results in tissue injury. In redox biology, hormesis reflects the dual role of reactive oxygen species as both signaling mediators and potential sources of oxidative damage.[22]

As previously reported, ozone-derived reactive oxygen species and lipid oxidation products are transient signals able to activate, in cells, endogenous defence mechanisms. Experimental evidence indicates that such mild oxidative challenges enhance mitochondrial efficiency, upregulate antioxidant enzyme systems, and improve cellular tolerance to subsequent stressors. Conversely, excessive oxidative stimuli may disrupt redox homeostasis and negate potential benefits, underscoring the narrow therapeutic window of ozone-based interventions.

This hormetic model has important clinical implications for degenerative musculoskeletal diseases, where impaired adaptive capacity and defective stress-response signaling appear to contribute more to disease progression than acute oxidative injury. Therapeutic strategies that promote controlled activation of redox-sensitive pathways may therefore support tissue resilience and functional recovery. Within this context, ozone therapy represents a potential redox-modulating approach whose effects are critically dependent on dose, route of administration, and patient-specific factors. [23]

The concept of hormetic redox modulation also provides a theoretical model for understanding variability in clinical outcomes reported across ozone therapy studies. Differences in ozone concentration, treatment frequency, and route of administration may shift the biological response along the hormetic curve, resulting in either adaptive benefit, neutral or toxic effects. This means that therapeutic efficacy is not solely dependent on the presence of an oxidative stimulus, but on its precise calibration within a narrow biological window. [24]

2.3. Clinical Applications of Ozone Therapy in Intervertebral Disc Pathology

Intervertebral disc degeneration and herniation are characterized by progressive extracellular matrix breakdown, loss of proteoglycans and inflammatory changes that contribute to mechanical instability of the column and radicular pain. Chronic oxidative stress plays a contributory role in these processes through activation of matrix-degrading enzymes, inhibition of anabolic signaling, and induction of apoptosis and senescence in nucleus pulposus and annulus fibrosus cells, ultimately impairing disc homeostasis and repair capacity.[25]

Within this pathophysiological landscape, ozone therapy has been applied as a minimally invasive conservative intervention, most commonly via intradiscal or paravertebral administration. Clinical evidence derives from randomized controlled trials, prospective cohort studies, and large observational series evaluating ozone injections especially in patients with contained disc herniation and limited neurological deficits. Across these studies, intradiscal ozone therapy has been associated with significant reductions in radicular pain and disability scores, with outcomes that are generally comparable to those achieved with corticosteroid-based or other conservative pharmacological interventions in the short to medium term. Comparative studies suggest that while corticosteroids may provide more rapid early symptom relief, ozone therapy may offer a more sustained clinical benefit over follow-up, potentially reflecting differences in underlying mechanisms of action. Proposed effects of ozone include oxidation-induced reduction of proteoglycan content leading to decreased disc volume and intradiscal pressure, as well as modulation of periradicular inflammatory responses through redox-sensitive signaling pathways. [26,27,28,29,30,31,32,33,34] [Table 1].

Paravertebral administration, used either alone or as an adjunct to intradiscal injection, is thought to contribute additional analgesic and anti-edematous effects by influencing local cytokine release, muscle tone, and microcirculation. At this purpose, clinical protocols integrating ozone with corticosteroids or local analgesic interventions have also been explored in paravertebral muscular injection of ozone, aiming to couple the rapid anti-inflammatory effects of pharmacological agents with the proposed mechanical and biological actions of ozone. Although such approaches may enhance early pain control, available data do not consistently demonstrate clear superiority over ozone monotherapy at mid-term follow-up.[35,36,37,38,39,40,41,42][Table 2].

Overall, intradiscal ozone therapy appears to represent the most evidence-based viable option within the conservative management spectrum for selected patients, although ozone concentration, and injection technique need to be standardized.

2.4. Clinical Application of Ozone Therapy in Knee Osteoarthritis

2.4.1. Knee Osteoarthritis

Degenerative knee osteoarthritis is associated with chronic low-grade inflammation, progressive cartilage degradation, subchondral bone remodeling, and synovial dysfunction, processes in which oxidative stress and altered redox signaling play a key role. In this pathophysiologic condition, increased production of reactive oxygen species within the joint microenvironment has been linked to chondrocyte senescence, reduced extracellular matrix synthesis, and amplification of pro-inflammatory cytokine pathways, thereby accelerating structural and functional deterioration[42,43]

Intra-articular ozone therapy has been investigated as a conservative intervention in knee osteoarthritis primarily aimed at symptom control rather than structural modification. Randomized clinical studies report significant improvements in pain, joint stiffness, and functional scores following repeated low-dose ozone injections, particularly in patients with mild to moderate disease. Proposed mechanisms include modulation of synovial inflammation, transient activation of endogenous antioxidant protection systems, and improvement of local microcirculation.[44,45]

Comparative studies have evaluated ozone therapy against established intra-articular treatments such as corticosteroids, hyaluronic acid, and platelet-rich plasma (PRP). Corticosteroid injections are often associated with rapid pain relief, but their effects tend to diminish over time, whereas ozone therapy appears to produce a more gradual improvement with sustained benefits at short- to mid-term follow-up. Comparisons with hyaluronic acid generally indicate comparable clinical outcomes in terms of pain reduction and functional improvement, although differences in injection protocols and outcome measures limit direct equivalence. More recent studies comparing ozone with PRP suggest that both interventions can significantly improve symptoms, with PRP potentially offering longer-lasting effects in selected patients, particularly in earlier stages of osteoarthritis. However, ozone therapy has been associated with simpler administration, lower procedural complexity, and reduced cost.[46,47,48,49,50,51,52,53,54,55,56] [Table 3].

On the whole, the available clinical evidences support ozone therapy as a potential alternative or adjunctive intra-articular option for symptomatic management of knee osteoarthritis. Nonetheless, heterogeneity in ozone concentrations, treatment schedules, and follow-up duration remains substantial, underscoring the need for standardized head-to-head trials to better define comparative effectiveness, durability of response, and optimal patient selection.

2.5. The Use of Ozone in Other Degenerative Musculoskeletric Diseases

Beyond intervertebral disc disease and knee osteoarthritis, ozone therapy has been investigated in a range of other degenerative and overuse-related musculoskeletal conditions, including hip osteoarthritis, hand osteoarthritis, and lateral epicondylitis, as well as shoulder tendinopathies and myofascial pain syndromes.[57,58,59] Despite differences in anatomical location and biomechanical loading, these disorders share common pathophysiological features such as localized inflammation, microvascular dysfunction, and increased ROS amount within affected tissues.

In hip osteoarthritis, clinical studies evaluating periarticular or intra-articular ozone injections report reductions in pain intensity and improvements in mobility and functional scores, with outcomes comparable to other conservative injective therapies in short-term follow-up[.60] Hand osteoarthritis has been explored in smaller randomized and observational studies, in which local ozone administration was associated with pain reduction and improvements in hand function and grip strength, particularly in patients with symptomatic interphalangeal joint involvement.[61] In lateral epicondylitis, ozone therapy has been assessed as an alternative to corticosteroid injections, with reported benefits in pain reduction and functional recovery, especially at mid-term follow-up[.62]

Additional investigations in shoulder disorders, including rotator cuff tendinopathy and adhesive capsulitis, suggest that ozone injections may reduce pain and improve range of motion, particularly when combined with physiotherapy or exercise-based rehabilitation Although these findings are encouraging, the overall evidence base for these indications remains limited by small sample sizes, heterogeneity in treatment protocols, and short follow-up durations. Consequently, ozone therapy in these conditions should be regarded as an adjunctive option within conservative management strategies, pending confirmation through larger, condition-specific randomized controlled trials.[63]

4. Discussion

4.1. From Mechanistic Plausibility to Clinical Evidence: Bridging the Gap

The body of evidence reviewed here points to a consistent, if circumscribed, conclusion: in patients with degenerative musculoskeletal disease, ozone therapy administered within validated concentration ranges produces short- to mid-term reductions in pain and disability that are broadly comparable to those achieved with established conservative interventions. This convergence of findings across anatomically and pathophysiologically distinct conditions — lumbar disc herniation, knee osteoarthritis, and several overuse-related disorders — lends biological credibility to the hypothesis that a shared mechanism, the redox modulation, may underlie the observed clinical benefits. Yet the critical distance between mechanistic plausibility and demonstrated efficacy remains substantial, and it is this gap that most limits the current appraisal of ozone therapy.

The strongest preclinical support for ozone derives from experimental models demonstrating Nrf2 nuclear translocation, upregulation of glutathione-related enzyme systems, modulation of NF-κB-dependent pro-inflammatory signaling, and transient improvements in mitochondrial efficiency following controlled ozone exposure [20,21]. These findings are internally coherent and consistent with the hormetic mechanism of action: at micromolar concentrations, ozone-derived reactive oxygen species and lipid oxidation products function as transient intracellular messengers rather than cytotoxic agents [22,23]. The translation of this model into clinical benefit, however, rests on an inference that has never been directly tested in human tissue. Among the randomized trials reviewed, not a single study embedded longitudinal redox biomarker assessment — no glutathione redox ratios, no Nrf2 target gene expression profiles, no advanced glycation end-products or 8-isoprostane measurements — at doses actually administered to patients. As a result, the mechanistic narrative, however compelling experimentally, remains unvalidated at the clinical level.

4.2. Protocol Heterogeneity as a Structural Barrier to Synthesis

Protocol heterogeneity in ozone therapy research represents more than a methodological inconvenience: it is fundamentally incompatible with the hormetic model on the basis of the ozone clinical efficacy. Trials reviewed here employed ozone concentrations ranging from 10 to 40 µg/mL, with variable injection volumes, differing anatomical targets, and divergent co-interventions — corticosteroids, hyaluronic acid, exercise programs — applied inconsistently across study arms. Hormesis predicts that the relationship between oxidative stimulus and biological response is nonlinear and threshold-dependent: concentrations below the adaptive zone produce no effect, those within it activate cytoprotective pathways, and those above it cause tissue injury [21,22]. This prediction implies that concentration and dosing precision are not secondary parameters but primary determinants of outcome. Yet no trial has explicitly mapped a dose-response curve or stratified patients by baseline redox status to identify where individual subjects fall on the hormetic curve.

This heterogeneity also precludes meaningful cross-study comparisons and renders meta-analytic pooling statistically questionable regardless of effect size estimates. The systematic review by Steppan et al., which pooled nearly 8,000 patients across multiple cohorts, demonstrated aggregate effectiveness for intradiscal ozone but also underscored that complication rates and outcome definitions varied so substantially across centers that aggregate figures may obscure clinically important subgroup differences [32]. More recent meta-analyses confirm pain reduction at the aggregate level while acknowledging that concentration, route, and co-treatment heterogeneity prevent definitive conclusions about optimal protocols Cao 2025 [30]. Establishing consensus-derived, condition-specific protocols is therefore not merely an academic exercise but a prerequisite for reliable efficacy assessment.

4.3. Blinding Challenges and the Contribution of Non-Specific Effects

Blinding is structurally problematic in ozone injection trials. The gas has a recognizable odor detectable by operators, and the tactile and pressure sensations accompanying injection of a gaseous medium create sensory cues that saline or sham needling cannot plausibly replicate. These constraints have led most trials to use oxygen as the control condition — a design that introduces a distinct confound, since hyperoxia is itself biologically active: it modulates vascular tone, reduces baseline hypoxia-inducible signaling, and may influence redox-sensitive pathways independently of ozone-specific effects [8,19]. The observed between-group differences in ozone versus oxygen trials may therefore reflect the magnitude of the ozone-specific pharmacological effect, a nonspecific response to gaseous injection per se, differential placebo amplification driven by the novelty and invasiveness of the procedure, or some combination of all three. Procedural placebo effects in chronic musculoskeletal pain trials are well-documented, often substantial, and rarely adequately quantified in ozone studies.

This limitation does not invalidate the clinical signals observed, but it demands that reported effect sizes be interpreted conservatively. Trials comparing ozone to inert sham — needle insertion without gas delivery, or subtherapeutic volumes with objective blinding verification — are needed before the specific contribution of ozone can be disentangled from contextual and expectancy effects. Pre-registration, pre-specified analysis plans, and CONSORT adherence are non-negotiable in this context.

4.4. Statistical Significance, Clinical Relevance, and the Absence of Structural Endpoints

Many of the trials reviewed report statistically significant reductions in visual analogue scale (VAS) scores or disability indices without explicitly reporting whether these reductions meet or exceed the minimal clinically important difference (MCID) for the relevant instrument. A VAS reduction of 1.5 points, for example, may reach statistical significance in an adequately powered trial while remaining below the threshold that patients perceive as meaningful improvement. The absence of systematic MCID reporting in ozone trials makes it difficult to translate statistically positive results into clinical guidance.

More consequentially, no published trial has incorporated structural endpoints — serial MRI-assessed disc hydration indices, quantitative cartilage volume measurements, or subchondral bone integrity scores — as primary or secondary outcomes. Without structural data, ozone therapy cannot be characterized as disease-modifying regardless of pain outcomes. The available evidence supports its characterization as a symptom-modulating intervention in selected patients with relatively preserved tissue architecture and impaired redox-inflammatory signaling; it does not support claims of structural disease modification. Trials of at least 24 months incorporating structural imaging alongside patient-reported outcomes are required before any revision of this assessment is warranted.

4.5. Safety Data: Reassuring in Controlled Settings, Incomplete in Real-World Practice

Within the concentration ranges employed in the clinical trials reviewed — predominantly 10–40 µg/mL for intra-articular and paraspinal applications — adverse events were generally mild, transient, and self-limiting. The most commonly reported reactions include injection-site discomfort, transient post-procedural pain exacerbation, localized hematoma, and occasional vasovagal episodes, all resolving without specific intervention. The meta-analysis by Steppan et al. reported a complication rate well below 1% across approximately 8,000 patients, a figure that has been broadly corroborated in subsequent controlled series [32]. A review similarly found that seven independent systematic reviews consistently identified a low prevalence of minor adverse events attributable to ozone therapy for knee osteoarthritis [64].

These reassuring aggregate figures, however, must be contextualized carefully. Trial populations are highly selected, follow-up periods short, and the operator expertise characteristic of academic interventional centers may not be reproducible in routine clinical settings. Small trial samples are statistically underpowered to detect rare but clinically serious events, meaning that the true incidence of severe complications is almost certainly underestimated in the published literature. Serious adverse events have been documented outside the controlled trial setting. Rouhi et al. reported neurological complications — including thalamic and cerebellar MRI signal abnormalities consistent with vascular or oxidative injury — following ozone injections, noting that improper needle placement and inadvertent intravascular injection represent the primary pathophysiological mechanisms [65]. Chirumbolo et al. specifically attributed documented serious complications to protocol deviations and inadequate operator training, emphasizing that the safety profile of ozone therapy is critically contingent on adherence to validated procedures [66]. Epidural abscess, nerve injury, cauda equina syndrome, and pneumoperitoneum following intradiscal or paravertebral injection have been described in case reports and small series, underscoring that serious harm, while uncommon under supervised conditions, is not negligible [67,68].

A separate, and arguably more pressing, safety concern pertains to the absence of regulatory standardization. Ozone therapy remains unapproved by the U.S. Food and Drug Administration for musculoskeletal indications, and its regulatory status varies substantially across European, Asian, and Latin American jurisdictions. In some settings, treatment is administered outside accredited facilities with unvalidated gas concentrations and poorly characterized equipment — conditions that introduce risks of incorrect dosing, iatrogenic infection, and tissue injury that are absent from controlled trial data. Long-term safety is additionally unaddressed: cartilage, intervertebral disc, and tendon exhibit limited intrinsic regenerative capacity, and the theoretical risk that serial oxidative challenges from repeated injections might accelerate the matrix degradation and cellular senescence that ozone therapy is intended to prevent has never been evaluated in a longitudinal study extending beyond 12–24 months. Acceptable short-term safety in controlled settings must not be conflated with a clean long-term safety record. Future studies must adopt standardized adverse event reporting frameworks and track patients for sufficient duration to capture delayed or cumulative harms [69,70].

4.6. Clinical Positioning and Evidence Hierarchy

There is no doubt that ozone therapy occupies a defensible but carefully circumscribed position in musculoskeletal medicine: it is a mechanistically credible, symptomatically useful adjunctive option for patients with mild-to-moderate degenerative disease who have not responded adequately to conventional conservative measures and who wish to defer surgical intervention. This positioning applies most clearly to patients with symptomatic lumbar disc herniation and mild-to-moderate knee osteoarthritis, conditions for which the controlled trial evidence is most extensive. For other anatomical sites — hip, hand, shoulder, lateral epicondyle — the evidence base is smaller and more heterogeneous, justifying a more cautious interpretive stance.

However, ozone therapy is not, on current evidence, a disease-modifying treatment or a standalone standard of care for any degenerative musculoskeletal condition. Publication bias must also be acknowledged: a disproportionate share of clinical trials originates from investigators with established ozone programs or from industry-supported device studies. Independent, publicly funded, multicenter trials conducted under pre-registered protocols represent the way to a scientifically correct assessment of efficacy.

5. Conclusions

Ozone therapy for degenerative musculoskeletal disease rests on a coherent and experimentally grounded biological rationale: controlled, dose-dependent oxidative signaling activates Nrf2-mediated cytoprotective pathways and modulates redox-sensitive inflammatory cascades through a mechanism consistent with the hormetic model. Based on a series of experimental knowledges, ozone does not function as an exogenous antioxidant or a direct anti-inflammatory agent; rather, it acts as a calibrated redox stimulus capable of restoring adaptive cellular resilience in tissues where endogenous redox-regulatory mechanisms are chronically impaired.

Clinical results, particularly from randomized controlled trials published between 2020 and 2025, indicates that ozone therapy produces short- to mid-term improvements in pain and functional outcomes that are comparable to corticosteroid injections, non-inferior to microdiscectomy in selected patients with lumbar disc herniation, and broadly equivalent to hyaluronic acid for symptomatic knee osteoarthritis over similar follow-up periods. These findings are consistent across multiple anatomical sites and study designs, lending them greater credibility than any single trial could provide in isolation.

Nevertheless, current evidences showed substantial methodological limitations that prevent definitive conclusions. The specific contribution of ozone — as distinct from the nonspecific effects of gaseous injection, procedural expectancy, and active oxygen comparators — has not been adequately isolated in any published trial. No study has validated the proposed mechanism of Nrf2-mediated redox modulation in human tissue at clinically administered doses. Protocol heterogeneity across trials is pervasive and incompatible with the precision required by the hormetic model. Structural endpoints documenting disease modification are entirely absent. Short-term safety in controlled, academically supervised settings is acceptable, but the true incidence of serious complications in private clinical practice is unknown and long-term safety data beyond 24 months are lacking.

Consequently, advances in the field of the use of ozone in the treatment of musculoskeletric diseases requires a systematic and methodologically disciplined research agenda. On the basis of the above reported data, the following priorities are identified: (1) sham-controlled randomized trials employing inert comparators — needle insertion without gas delivery or subtherapeutic volumes — with objective blinding verification and adequate statistical power; (2) standardized ozone concentration, gas mixture ratio, injection volume, anatomical target, and treatment frequency across trials, ideally derived through formal consensus processes; (3) follow-up of at least 24 months incorporating structural imaging endpoints alongside patient-reported pain and functional outcomes; (4) embedded longitudinal redox biomarker panels — glutathione redox ratio, lipid peroxidation products, Nrf2 target gene expression, inflammatory cytokines, matrix turnover markers — to test whether clinical response and biological mechanism are linked; (5) pre-treatment stratification by disease stage and systemic oxidative stress profile to identify the subgroups most likely to benefit from redox-modulating intervention; and (6) standardized adverse event reporting using validated frameworks such as the Common Terminology Criteria for Adverse Events (CTCAE), with prospective registries capturing real-world complication data across diverse practice settings.

Until this evidence exists, clinical adoption of ozone therapy should remain cautious, protocol-driven, and accompanied by transparent informed consent that accurately represents the investigational nature of the intervention. The biological rationale for ozone therapy is sufficiently robust to justify continued rigorous investigation, but it not supports uncritical clinical expansion. Realizing the therapeutic potential of this approach will require the same methodological discipline demanded of any emerging intervention — mechanistic rigor, protocol standardization, and n extended follow-up able to clarify lasting benefit and delayed harm.