Last time I did research on glucosamine it showed that it is best taken with chondroitin. However MSM (methyl-sulfonyl-methyl) works the same way in the body and is usually less expensive.
They are both used as a source of sulfonyl groups, which are mostly found in the body in connective tissue. My research was quite some time ago but I’ve take MSM by itself since then.
Taking MSM, gucosamine and chondroitin is like taking two things for the same problem. One or the other should suffice if the concentrations are the same as the combination.
It takes a few weeks for the levels to make the effect noticeable.
Again, my research was done some time ago, things may have changed a little but the underlying mechanism should still be the same.