In summary, the research suggests consistently that glucosamine (and especially in combination with MSM) has a positive effect on may people with arthritis.  It is not successful for everyone, of course, and there are conflicting studies that may relate to other factors, dose and time.  Glucosamine + MSM has been shown to be as effective as the more expensive chondroitin in several studies.  The recommendation is consistent throughout the research that the supplement must be taken at prescribed dose for 90 days to judge effectiveness and it is worth a try!

Glucosamine and chondroitin for osteoarthritis.

Synovial and plasma glucosamine concentrations in osteoarthritic patients following oral crystalline glucosamine sulphate at therapeutic dose

Comparison of Glucosamine-Chondroitin Sulfate with and without Methylsulfonylmethane in Grade I-II Knee Osteoarthritis: A Double Blind Randomized Controlled Trial.

Methylsulfonylmethane and boswellic acids versus glucosamine sulfate in the treatment of knee arthritis: Randomized trial.

Randomised, Double-Blind, Parallel, Placebo-Controlled Study of Oral Glucosamine, Methylsulfonylmethane and their Combination in Osteoarthritis.

Effects of glucosamine sulfate on the use of rescue non-steroidal anti-inflammatory drugs in knee osteoarthritis: Results from the Pharmaco-Epidemiology of GonArthroSis (PEGASus) study

Evaluation of the anti-inflammatory actions of various functional food materials including glucosamine on synovial cells.

Natural Products for Promoting Joint Health and Managing Osteoarthritis.

Comparative effectiveness of glucosamine, chondroitin, acetaminophen or celecoxib for the treatment of knee and/or hip osteoarthritis: a network meta-analysis.

Efficacy and safety of a compound supplement containing glucosamine, chondroitin, and five bioactive ingredients in volunteers with knee joint pain

Glucosamine promotes osteoblast proliferation by modulating autophagy via the mammalian target of rapamycin pathway

Use of glucosamine and chondroitin supplements and risk of colorectal cancer

Molecular mechanisms of anticancer effects of Glucosamine.

The Fate of Oral Glucosamine Traced by (13)C Labeling in the Dog.

Chondroitin sulfate and glucosamine sulfate associated to photobiomodulation prevents degenerative morphological changes in an experimental model of osteoarthritis in rats.

Evaluation of the effect of glucosamine on an experimental rat osteoarthritis model