The hips and knees are particularly affected, causing pain and limitation of motion. In recent years, glucosamine, a substance important in the building of cartilage, has become immensely popular. It is now one of the most widely used of the dietary supplements, and is advertised as promoting joint health.
Nobody knows for sure.
They also summarized the data on chondroitin sulfate, another substance important in building cartilage. All the studies on both substances were focused on arthritis of the knees. All of these studies were done in Europe and, in many of them, the authors were associated with the drug manufacturers. There is no analysis of the characteristics or age of those taking the supplements, and inadequate analyses on duration of treatment and dosage used. Then, there is the issue of an early bias in reporting - the tendency for positive studies to be published earlier than negative studies.