Widely used oral joint supplement in both horses and humans. In horses it is used either to treat a lame horse or as a preventative to delay the onset of lameness caused by e.g., Osteoarthritis. In lameness cases the precise cause of the lameness is often never properly diagnosed before glucosamine supplementation is begun.
Glucosamine is an important component of complex glycosaminoglycan molecules found in joints and their lubricating joint fluid. In joint supplements it is often combined with Chondroitin Sulphate which is another component of proteoglycans found in joints. The theory is that these compounds, by provision of raw materials, will help replenish damaged or degraded joint cartilage and perhaps by modifying the inflammatory response to joint injury, reduce joint inflammation. Numerous laboratory and animal trials have been undertaken to support or disprove the theories. Interpretation of the trial results has been complicated and muddied by the use of different chemical compounds of glucosamine and widely varied dose rates.
Several factors in the live horse may influence the activity of glucosamine including bioavailability – how much is actually absorbed, which seems to be low, how much reaches the target joint(s) and the degree of inflammation present in those joints as well as its cause. To date, clinical trials have failed to prove useful effect of glucosamine in horses. Further, the results of some extremely large human trials such as the human knee joint study undertaken across the EU, failed to prove any beneficial effect for glucosamine as a supplement for knee arthritis.
Poor regulation of such supplements means that exaggerated claims of efficacy are rife and the quality of the products, including the content of actives claimed by the label, is unreliable.