The pain gain in the largest trials is too small to feel
In trials of more than 200 people each came in 0.3 to 0.5 cm better than placebo on a 10 cm pain scale, short of the 0.9 cm the authors set as noticeable.
What the study found
In the ten biggest trials, no pain difference a patient would notice
Restricted to trials of more than 200 people, glucosamine, chondroitin and the pair each came in between 0.3 and 0.5 cm better than placebo on a 10 cm pain scale. The authors had fixed 0.9 cm in advance as the smallest difference a patient would feel. None of the three reached it.
The caveat · The 0.9 cm bar is the authors' own
The 0.9 cm threshold is these authors' own choice rather than an agreed one, and a reader accepting a smaller threshold would read some of these intervals differently. Restricting by trial size excludes most of the older positive literature, so this is not the body of trials other reviews pool.