It's probably safe—but there's no good evidence that it works

People with joint pain, including those with osteoarthritis, are consuming large quantities of glucosamine as a result of a huge volume of recent media coverage on its possible value. Reviews and leading articles in medical journals have variously labelled it a magical new treatment,1 criticised the “hype,”2 or, more commonly, been non-committal.3 Perhaps we are just confused.

Glucosamine is a sugar, a sulphated amino-monosaccharide, one of the constituents of the disaccharide units present in articular cartilage proteoglycans. In vitro work has shown that it can alter chondrocyte metabolism, and this is the rationale usually given for its use in osteoarthritis.4 However, it is unclear whether oral glucosamine can reach chondrocytes in vivo,3 and in addition to the oral compound (the commonly available form), injectables and local preparations have been subjected to clinical trial.5^–8 The most appropriate dose and route of administration remain unknown. We do not even seem to know how to classify it: is it a drug, a food supplement, a nutriceutical, or a complementary therapy?

Osteoarthritis is a heterogeneous and poorly understood …