Viscosupplementation using intra-articular hyaluronic acid (HA) injections is a widely used treatment option for knee osteoarthritis (OA), but evidence supporting its clinical effectiveness is mixed and subject to ongoing debate.
Guideline-based evidence from the UK and Australia generally recommend against the routine use of intra-articular HA for knee OA, reflecting that current high-quality randomized controlled trials (RCTs) and meta-analyses demonstrate only small, clinically irrelevant improvements in pain and function compared to placebo, alongside potential risk of harms. The Australian Osteoarthritis of the Knee Clinical Care Standard strongly advises not offering HA injections due to lack of clinically important benefit and concerns about adverse events, including rare but serious risks like septic arthritis and severe inflammatory reactions. Additionally, the unnecessary costs and environmental impacts associated with imaging-guided HA injections are highlighted as further reasons to limit use NICE CKS,NICE NG226,Pisaniello et al. 2026 Pisaniello et al. 2026 Samson et al. 2007.
However, the scientific literature presents nuances that suggest viscosupplementation remains a viable option for certain patients, especially those with early or mild-to-moderate knee OA seeking symptom relief. Systematic reviews of multiple meta-analyses indicate that intra-articular HA can provide a reduction in pain and improvement in function versus placebo lasting up to 26 weeks, demonstrating a favorable safety profile when compared with alternatives such as corticosteroids and oral NSAIDs Campbell et al. 2015 Jevsevar et al. 2015. The benefits, although modest, may be more pronounced with newer HA formulations that employ advanced chemical modifications to improve rheological properties, residence time, and biological activity.
Recent developments in viscosupplementation involve chemically modified HA products, such as Hymovis® and Hymovis ONE®, which utilize reversible hydrophobic moieties to enhance viscoelasticity, shock absorption, and enzymatic resistance without the downsides of cross-linked HA. Clinical studies report significant improvements in pain, joint function, and quality of life up to 12 months after treatment with such products, with evidence also supporting their use in meniscal tear healing and active individuals with joint overuse injuries. Comparative trials show these newer formulations may provide longer-lasting relief than corticosteroids and similar efficacy to established cross-linked HA products with fewer side effects Benazzo & Bernetti A 2026.
Underlying mechanisms beyond simple viscosupplementation include biological effects whereby HA interacts with cellular receptors to modulate inflammation, stimulate endogenous HA production, and exert chondroprotective effects. The efficacy of HA is influenced by its molecular weight and chemical structure: high molecular weight linear HA (>2 million Daltons) exhibits superior biological activity compared to low molecular weight or cross-linked products. These biological actions contribute to a therapeutic benefit that may exceed what is predicted by purely mechanical considerations de Campos & Cliquet A 2025.
In summary, the current evidence supports a cautious and individualized approach to viscosupplementation for knee OA:
- UK and Australian guidelines currently recommend against routine use of intra-articular HA injections for knee OA due to limited clinical benefit and safety considerations NICE CKS,NICE NG226,Pisaniello et al. 2026 Pisaniello et al. 2026 Samson et al. 2007.
- Systematic reviews of meta-analyses show viscosupplementation provides small but statistically significant improvements in pain and function versus placebo lasting up to 26 weeks, with a good safety profile versus other treatments Campbell et al. 2015 Jevsevar et al. 2015.
- Newer HA formulations with improved rheological and biological properties, such as the chemically modified Hymovis® products, have shown promising clinical outcomes with extended duration of symptom relief, better tolerability, and potential to support tissue healing, suggesting they may be appropriate for selected patients Benazzo & Bernetti A 2026.
- Clinical benefit appears to depend on the molecular weight and chemical structure of HA, with high molecular weight linear HA demonstrating superior biological activity including anti-inflammatory and chondroprotective effects de Campos & Cliquet A 2025.
- Shared decision-making with patients is critical, incorporating discussion of the modest efficacy, potential risks, alternative therapies, and patient preferences Pisaniello et al. 2026 Pisaniello et al. 2026.
Overall, while viscosupplementation is not endorsed as standard care by UK guidelines, evolving evidence indicates a nuanced role for advanced HA products in the multimodal management of knee osteoarthritis, especially when other treatments have failed or are contraindicated.
Key References
- NICE CKS: Osteoarthritis
- NICE NG226: Osteoarthritis in over 16s: diagnosis and management
- SmPC: Capsaicin 0.025% w/w Cream
- SmPC: Zacin 0.025% w/w Cream
- SmPC: Adcortyl Intra-Articular/Intradermal Injection 10mg/ml
- SmPC: Dexamethasone 3.3 mg/ml solution for injection/infusion
- NICE CKS: Gout
- (Samson et al., 2007): Treatment of primary and secondary osteoarthritis of the knee.
- (Campbell et al., 2015): Is Local Viscosupplementation Injection Clinically Superior to Other Therapies in the Treatment of Osteoarthritis of the Knee: A Systematic Review of Overlapping Meta-analyses.
- (Jevsevar et al., 2015): Viscosupplementation for Osteoarthritis of the Knee: A Systematic Review of the Evidence.
- (Pisaniello et al., 2026): Intra-articular hyaluronic acid (viscosupplementation) for osteoarthritis: is it effective?
- (Benazzo and Bernetti A., 2026): Rheological properties and clinical efficacy of a chemically modified hyaluronic acid for joint health enhancement.
- (de Campos and Cliquet A., 2025): Current Concepts in Viscosupplementation: New Classification System and Emerging Frontiers.