Glucosamine and Omega-3 for Knees: What the Evidence Says

Why people turn to glucosamine and omega-3 for knee pain

Knee cartilage wears down with age, bringing more frequent pain and stiffness. This degenerative change, osteoarthritis, is common in people in their 50s and 60s, and many reach for glucosamine or omega-3 hoping to protect cartilage and ease pain. The research, however, is less clear-cut than the marketing, so let's look at what it actually says.

Glucosamine: mixed results

• GAIT trial (NEJM, 2006): 1,583 people with knee osteoarthritis took glucosamine 1,500 mg, chondroitin 1,200 mg, both, an anti-inflammatory painkiller (celecoxib), or a placebo for 24 weeks. The share whose pain fell by 20% or more was 60.1% with placebo, 64.0% with glucosamine, 65.4% with chondroitin, and 66.6% with both, none significantly different from placebo; only celecoxib, at 70.1%, was significantly better. That 60% of the placebo group improved shows why "I feel better" alone cannot prove a supplement works.
• Cochrane review: When only rigorously designed, high-quality trials were pooled, pain improved about as much with glucosamine as with a placebo. Pooling all trials showed a slightly better result than placebo, a difference the reviewers said was hard to explain.
• US NCCIH (National Center for Complementary and Integrative Health): concludes it is still unclear whether glucosamine helps knee osteoarthritis symptoms. Professional bodies disagree: the American College of Rheumatology (2019 guideline) and the Osteoarthritis Research Society International (OARSI, 2019) strongly recommend against glucosamine for knee osteoarthritis, while the American Academy of Orthopaedic Surgeons (2021 guideline) says it may help people with mild to moderate disease.
• Mayo Clinic: notes the results are mixed, but since side effects are few and it is inexpensive, it may be worth trying when other treatments have not worked.

In short, glucosamine is a supplement with conflicting evidence, not one that reliably works.

Omega-3 and inflammation: the evidence

EPA and DHA from oily fish are known to be involved in regulating inflammation. In rheumatoid arthritis, they may help when added to standard treatment, but the NIH Office of Dietary Supplements (ODS) says it is not clear whether they actually reduce pain, swelling, or stiffness. For knee osteoarthritis, the evidence is even more limited, so the fair summary is "possible, but not proven."

Which joint ingredients does Korea's MFDS recognize?

In Korea, the main ingredients officially listed for the function "may help joint and cartilage health," with their daily amounts, are below. This function does not mean the ingredient treats osteoarthritis, and some individual products have other approved ingredients, so check the function statement on the label.

Reference amounts for adults over 65

• Omega-3 (ALA): The NIH ODS sets an adequate intake of 1.6 g for men and 1.1 g for women (the same after 65). In Korea, the MFDS range for EPA/DHA supplements is 500–2,000 mg a day for the circulation and triglyceride claim; no joint function is recognized.
• Glucosamine: The MFDS range is 1,500–2,000 mg a day, and 1,500 mg a day is the amount most studies used. Since studies usually assessed effects after three months or more, it is reasonable to try it for about three months and reconsider if nothing changes (our suggestion based on study durations, not an official recommendation).

Who needs to be careful?

• Shellfish allergy: Glucosamine is usually extracted from crab or shrimp shells and may trigger an allergic reaction (Mayo Clinic).
• Taking anticoagulants such as warfarin: Both glucosamine and omega-3 may raise bleeding risk. The US FDA advises keeping omega-3 supplements to no more than 5 g of EPA + DHA a day.
• Diabetes: Glucosamine has been reported to raise blood sugar in some people (NCCIH), so check with your care team first.
• If you take any other medication, ask your doctor or pharmacist about interactions before you start.

What to prioritize before supplements

Korea's KDCA health portal lists weight management and regular exercise as the foundation of osteoarthritis care: low-impact activity such as walking, swimming, or an exercise bike, 3–4 times a week for 30 minutes a day. According to the Arthritis Foundation, every pound of weight you lose takes about four pounds of pressure off your knees. Weight control and exercise are more dependable than any supplement.

When to see a doctor

• The joint makes noises, swells, and keeps hurting
• Your joints keep stiffening up in the morning
• The pain continues regardless of movement
• Sudden severe swelling, warmth, or redness appears

An accurate diagnosis relies on imaging such as X-rays or MRI, so if symptoms keep coming back or get worse, see an orthopedic specialist or a rheumatologist.