Whereas glucosamine is essential for maintaining healthy cartilage by promoting its formation and repair, chondroitin is thought to attract fluid into the cartilage and enhances its elasticity. It is also purported to inhibit the enzymes that break-down cartilage.
A meta-analysis of 7 studies, with a total of 700 patients, all compared with placebo, and in which additional analgesic drugs could be used, showed that chondroitin sulphate had significantly improved benefit over placebo.
In all trials chondroitin sulphate resulted in a significant reduction of analgesic or non-steroidal anti-inflammatory drugs (NSAIDs), and this was much more significant than for placebo.
Improvements showed after two to four months, with even better improvement after six months. Interestingly, adverse effects were reported more frequently with placebo than with chondroitin.