The claimEvidence A · guideline-tier
Glucosamine cures knee pain
The evidence
In the large GAIT trial (2006, NEJM) the main result was negative — no benefit was shown. A signal in people with moderate-to-severe pain did not pass the analysis set in advance.
Why the claim spreads
One of the most heavily advertised joint supplements for decades; early small studies plus the intuitive 'rebuild the cartilage' story keep it alive long after larger trials.
The mechanism, in brief
Glucosamine and chondroitin are the two supplements middle-aged and older people buy most often to protect their knees and ease joint pain. They really are raw materials of joint cartilage, but whether swallowing them gets anything to the knee is another matter.
Sources (1)
- Clegg, D. O., Reda, D. J., Harris, C. L., Klein, M. A., O'Dell, J. R., Hooper, M. M., et al. (2006). Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis. New England Journal of Medicine, 354(8), 795-808. 1,583 patients, 24 weeks: glucosamine 1,500 mg, chondroitin 1,200 mg, both, celecoxib 200 mg or placebo. Response (>= 20% pain reduction) with placebo 60.1%; glucosamine +3.9 points (P = 0.30), chondroitin +5.3 (P = 0.17), combination +6.5 (P = 0.09), celecoxib +10.0 (P = 0.008). Assignment was stratified by pain severity (mild n = 1,229; moderate to severe n = 354); in the moderate-to-severe stratum the combination responded 79.2% vs 54.3% (P = 0.002), which the authors call exploratory (abstract, PMID 16495392).