Przejdź do treściA recent double-blind randomized trial found no significant advantage over placebo for undenatured type II collagen, pharmaceutical-grade crystalline glucosamine sulfate, or diacerein in patients with mild to moderate knee osteoarthritis. The study is clinically useful because all three commonly discussed oral treatments were assessed within the same four-arm, placebo-controlled protocol, with more than 96% of participants completing follow-up.
Polish version: Kolagen typu II, glukozamina i diacereina w gonartrozie — bez przewagi nad placebo
Why is this study worth attention?
Oral agents often described as slow-acting treatments for osteoarthritis remain widely used despite inconsistent evidence of benefit. Glucosamine is particularly controversial, but similar questions apply to undenatured type II collagen and diacerein. The trial by Narkbunnam and colleagues, published online on 9 September 2026 in JB & JS Open Access, tested all three strategies under a single protocol against a common placebo group.
Study question and methods
The four-arm, double-blind randomized trial enrolled 216 adults in Thailand with symptomatic Kellgren-Lawrence grade 2 or 3 knee osteoarthritis. For 24 weeks, participants received one of the following:
- undenatured type II collagen, 40 mg once daily,
- pharmaceutical-grade crystalline glucosamine sulfate, 500 mg three times daily,
- diacerein, 50 mg once or twice daily,
- or placebo.
The primary endpoint was total WOMAC score at 24 weeks, with follow-up extended to 36 weeks. The analysis followed the intention-to-treat principle, using imputation and repeated-measures models to account for missing data.
Overall, 208 of 216 participants completed the study, a completion rate of 96.3%. Mean age was 61.7 years, 90.9% were women, and 73.6% had Kellgren-Lawrence grade 2 radiographic disease.
Results
At 24 weeks, none of the three active treatments was superior to placebo for the primary endpoint. The between-group differences in total WOMAC score versus placebo were:
- type II collagen: −4.7 points (95% CI −18.6 to 9.1),
- glucosamine: −8.1 points (95% CI −21.8 to 5.7),
- diacerein: −12.3 points (95% CI −25.9 to 1.3).
All confidence intervals crossed zero, and none of the comparisons demonstrated a clear difference exceeding the study’s threshold for minimal clinical importance. At 36 weeks, the pattern remained similar, with differences versus placebo of −1.8, −4.8 and −1.3 points, respectively.
No significant between-group differences were found for pain measures, joint-space width or performance tests. Adverse events were mild and similar across groups, and no serious adverse events were reported.
Clinical interpretation for an orthopaedic surgeon
The important point is not simply that the p values were above 0.05, but the size and precision of the observed effects. Point estimates for all three interventions favoured improvement, yet the effects were neither sufficiently precise nor sufficiently large to establish a reliable advantage over placebo. There was also no consistent supportive signal across secondary outcomes.
Clinically, these findings weaken the rationale for routinely using any of the three products as stand-alone treatment with the expectation of a substantial improvement in pain and function. The results may be especially useful when discussing realistic treatment benefit, cost and alternatives with better-established efficacy.
Limitations
The study was conducted in a Thai population, with a marked predominance of women and mostly Kellgren-Lawrence grade 2 disease. The findings therefore cannot automatically be assumed to apply identically to populations with different demographics or more advanced osteoarthritis.
Follow-up to 36 weeks is adequate for short-term symptomatic assessment but too short to support conclusions about long-term structural effects. The trial was also not designed to detect rare adverse events.
What might this change in practice — and what does it not prove?
The trial provides a strong argument against treating undenatured type II collagen, crystalline glucosamine sulfate or diacerein as routine monotherapy expected to deliver a clinically important improvement in knee osteoarthritis. It does not prove that no individual patient can improve, nor can the result be extrapolated automatically to every commercial formulation, different doses, combination therapy or patients with a different disease stage.
It also does not show that these interventions increase or reduce the long-term likelihood of joint replacement. Answering that question would require a substantially longer follow-up and a different study design.
Reference
- Narkbunnam R, Awirotananon K, Chareancholvanich K, Achawakulthep C, Adulkasem N, Chatmaitri S, Hirunyachoke P, Pornrattanamaneewong C. A Comparison of Clinical Outcomes Among Undenatured Collagen Type II, Glucosamine Sulfate, and Diacerein on Osteoarthritic Knee Treatment: A Randomized Clinical Trial. JB & JS Open Access. 2026;11(3). DOI: 10.2106/JBJS.OA.26.00225. PMID: 42698930.
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Content prepared by: Tomasz Poboży - orthopaedic surgeon.