Glucosamine(500Mils)should be taken with(400mils)of chondroitin sulfate to work.You can buy it mixed in one capsule.It worked for my sciatica and as previously stated ,makes your cartilege grow faster than you wear them out.If you have Rheumatoid Arthritis here is my cure.1000 mils.flax seed oil...50 mils. zink...1000 mils MSM(this is the newest wonder Element and causes no harm as its natural).I also take Cal-Mag with vitamin D.Must have vitamin D in order for body to absorb the Magnesium.About 15 months ago I got arthritis in both knees so bad I couldnt sleep and 1 week after taking the above herbs and vitamins I was fine.