Don’t expect glucosamine/chondroitin to treat knee osteoarthritis

Cost: Roughly 2–5 RMB per day, or 700–1800 RMB per year.
In plain terms: The GAIT trial involved 1583 participants with knee osteoarthritis who took the supplements for 24 weeks. In the placebo group, 60.1% reported reduced pain. Glucosamine only improved this rate by 3.9 percentage points (P=0.30), while chondroitin added 5.3 percentage points (P=0.17). Taking both together yielded a 6.5 percentage point improvement (P=0.09). All these differences are so small they could easily be due to chance. Spending 700–1800 RMB yearly essentially buys you the same placebo effect seen in 60% of participants.
Benefit: As noted above, glucosamine and chondroitin showed minimal benefits compared to placebo. The real active drug in the trial, celecoxib, produced a 10.0 percentage point improvement (P=0.008). The perceived value of glucosamine/chondroitin stems from their “cartilage-repair” reputation and the fact that placebo alone helped 60% of patients.
Evidence grade: A
Sources:Clegg DO et al. (2006). Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis. NEJM. https://doi.org/10.1056/NEJMoa052771
Notes: Controversy: Among participants with severe baseline pain, those taking both supplements saw a 79.2% pain-reduction rate versus 54.3% in the placebo group (P=0.002). However, researchers note this finding was derived post-hoc and should be viewed as a preliminary clue rather than a definitive conclusion. Proven treatments for knee osteoarthritis include weight loss and muscle-strengthening exercises — see Section 2.