Glucosamine: For Joint Health

A common question I get from my older clients and Masters athletes is:

What can I take for my knee pain?

Unfortunately, my recommendation is often refuted by other health practitioners who seem to have only read a headline, not the whole paper. 

I'll explain.  

Glucosamine should be one of the most popular supplements people reach for when knees start feeling stiff, creaky or “older than they should.” 

And it should be paired with chondroitin sulfate.

Together they can be simple way to support cartilage and keep your joints moving comfortably.

Unfortunately, there is a perception by many health practitioners that glucosamine is "less likely to help than a placebo". 

But what does high-quality research actually say?

One of the best-known trials in this area is the Glucosamine/chondroitin Arthritis Intervention Trial (GAIT), published in The New England Journal of Medicine in 2006.

It’s valuable because it wasn’t a small, loosely controlled supplement study - it was a large, well-designed clinical trial.

This article breaks down GAIT in plain English, explains what the results mean in real life and shows how to think about glucosamine for joint health (especially if your pain is more than “mild annoyance”).

What was the GAIT study?

GAIT was a multi-center, randomised, double-blind, placebo-controlled trial - the gold standard style of clinical study.

Researchers enrolled 1,583 adults with symptomatic knee osteoarthritis, then randomly assigned them to one of five groups for 24 weeks:

• Glucosamine hydrochloride: 1500 mg/da
• Chondroitin sulfate: 1200 mg/day
• Glucosamine + chondroitin (combination)
• Celecoxib: 200 mg/day (an arthritis medication used as an active comparator)
• Placebo

The main outcome they looked for was simple:

Did the person get at least a 20% reduction in knee pain by week 24?

In the overall group, glucosamine and chondroitin didn’t clearly beat placebo

Across all participants, neither glucosamine nor chondroitin - alone or together - significantly outperformed placebo for pain reduction.

This is the part where these other health practitioners stopped reading. 

But GAIT has an important second layer.

The key takeaway: the combination helped a specific subgroup (moderate-to-severe pain)

GAIT divided people by pain level at baseline:

• Mild pain (most participants)
• Moderate-to-severe pain (a smaller subgroup)

In people with moderate-to-severe knee pain, the combination (glucosamine + chondroitin) performed significantly better than placebo:

• 79.2% responded on the combo
• 54.3% responded on placebo
• This difference was statistically significant (P = 0.002)

In other words:

If your knee pain is mild, the benefit may be hard to detect.

If your knee pain is more significant, the combination is worth considering.

Why was the placebo response so high?

One reason GAIT is tricky to interpret is that the placebo response was unexpectedly high - around 60% improved even on placebo.

The authors discuss why this can happen in osteoarthritis trials, including:

• high expectations from participants
• the natural “ups and downs” of knee symptoms
• many participants starting with relatively mild pain, where standard pain scales can struggle to detect meaningful change

This doesn’t mean glucosamine “does nothing.”

It means detecting a true effect is harder when placebo improvements are large and symptoms are mild.

How fast does it work compared to medication?

Another useful GAIT finding: celecoxib worked faster.

By week 4, celecoxib showed quicker improvements.

The supplement groups improved more gradually over time.

That fits what many people experience: glucosamine/chondroitin tends to be a slow build, not a quick painkiller.

(The same often applies to collagen.)

What does this mean for “glucosamine for joint health”?

A practical way to interpret GAIT:

• For mild knee discomfort: glucosamine/chondroitin may not feel dramatically different from placebo and improvements can be subtle.
• For moderate-to-severe knee pain: the combination may be meaningfully more helpful than placebo for some people.
• Expect gradual change: think in weeks, not days.

What matters when choosing a glucosamine supplement?

GAIT also raised a very important point: supplement quality varies widely.

In GAIT, the ingredients were handled under an investigational drug framework and tested for purity and potency.

That level of quality control is not guaranteed across retail supplements.

So if you’re using glucosamine for joint health, quality and formulation matter - and combination formulas tend to make more sense than glucosamine alone.

A more complete joint approach

Joint pain isn’t only “cartilage chemistry.”

It’s also:

• inflammation signalling
• connective tissue integrity
• training load / movement habits
• body weight and metabolic factors
• micronutrient status and recovery

That’s why you should look for a broad, multi-ingredient joint formula rather than a single ingredient on its own.

If you want a combined approach that includes core joint ingredients (like collagen + glucosamine + chondroitin, alongside supportive cofactors), you can buy Complete Joint Care here:

Take Home Message

The GAIT trial didn’t find strong benefits for glucosamine or chondroitin across everyone with knee osteoarthritis - but it did find a clear signal for the combination in people with moderate-to-severe pain.

So the best “real world” take is:

• If your pain is mild: results may be modest (and start with 15g/day collagen)
• If your pain is more substantial: the combination is more defensible to trial.
• Give it time, and choose a formulation you trust.

Buy Complete Joint Care

About the Author

Grant Jenkins is the founder of Propel Health Australia and a high-performance coach & physiologist with over 25 years’ experience working with elite and developing athletes. He has formulated nutritional supplements used by athletes, families and health professionals across Australia. Grant combines real-world coaching experience with evidence-based research to bridge the gap between performance science and practical health.

 

Reference

Clegg DO, Reda DJ, Harris CL, et al. Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis. N Engl J Med. 2006;354(8):795–808. doi:10.1056/NEJMoa052771

Disclaimer

This content is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Always consult your Health Practitioner before starting any new supplement.