Does glucosamine help your joints?

Short answer

Barely. In an analysis of 3,803 people, pain fell by 0.4 points out of 10, short of the 0.9-point change people can feel, and the difference in joint space was tiny. The big effects came from one company's product and industry-funded trials.

Does glucosamine help your joints?
'Glucosamine → more cartilage building blocks → less joint pain' — does this formula hold?
Glucosamine is a building block of cartilage, so many people believe taking it makes joints stronger. We checked trials with thousands of people with knee pain to see whether pain and cartilage actually change.
The biggest trial
No difference from placebo
1,583 people with painful knee arthritis took glucosamine (1,500 mg a day), chondroitin, both, a painkiller or a placebo for 24 weeks. 60.1% on placebo had pain drop by 20% or more; glucosamine was 3.9 percentage points higher, which was no difference. The painkiller was 10.0 points higher.
Pooled trials say the same
Pain down 0.4 points; a change you can feel is 0.9
An analysis of 10 large trials with over 200 people each (3,803 people) found glucosamine lowered pain by 0.4 points out of 10 versus placebo. That fell short of the 0.9-point 'noticeable change' the researchers set in advance. The difference in the space between the joint bones (cartilage thickness) was tiny too.
So which studies showed big effects?
One company's product and industry-funded trials
In an analysis of 20 trials, the 10 trials using one company's (Rotta) product showed less pain, but trials of other products and the 8 most rigorously designed trials showed no effect. In the 3,803-person analysis, trials without industry funding showed effects 0.5 points smaller, close to 0.
What about slower cartilage wear?
A 0.25 mm difference over 3 years, from the same company's product
In a trial of 212 people over 3 years, joint space narrowed 0.31 mm on placebo and 0.06 mm on glucosamine. Both trials that showed slower progression over 3 years used the same company's product. In a 2-year trial of 605 people, glucosamine alone made no difference, and pain did not differ from placebo either.
What about the joints of people who train?
The trials studied people with painful arthritis
All of these trials studied people with painful arthritis of the knee or hip. None of them showed that glucosamine protects joints that do not hurt. Side effects were similar to placebo (the 1,583-person trial and the 20-trial analysis).
Bottom line: pain and cartilage barely changed
The effect was big only with one product and industry-funded trials
In the analysis of 3,803 people, pain fell 0.4 points out of 10, short of the noticeable 0.9 points, and the difference in joint space was tiny. The big effects were concentrated in one company's product and industry-funded trials. Glucosamine did almost nothing for joint pain.