An exhaustive systematic research of randomized, placebo-controlled clinical trials published or performed between January 1980 and March 2002 was conducted. The search assessed the structural and symptomatic efficacy of oral glucosamine sulfate and chondroitin sulfate in knee osteoarthritis through independent meta-analyses of the effects on joint space narrowing.  

The review of the literature, congressional abstracts and direct contact with the authors and manufacturers of glucosamine and chondroitin demonstrated the structural efficacy of glucosamine and indistinguishable symptomatic efficacies for both compounds. The authors concluded that additional studies are needed to investigate the relationship among time, dose, patient baseline characteristics and structural efficacy for an accurate, disease-modifying characterization of these two compounds, regarding the relatively sparse data on glucosamine and joint space narrowing and the absence of data on structural effects of chondroitin.