They don't work. There is no data that suggests glucosamine and chondroitin have any benefit for inflammation. It is possible that they do help osteoarthritic pain. One must give it a 3 month trial before deciding if these supplements are effective.
Usually two weeks. Primary active ingredient of such combination meds is the glucosamine and that usually takes approximately 2 weeks to attain full affect. These products are not successful for all patients so if you see no response by four weeks I would stop taking it.
Depends. Some people find that their osteoarthritis of the knees feel better while taking glucosamine this usually takes between 1 to 3 months. Studies on glucosamine's benefit have been conflicting. More controlled studies need to be done to test effectiveness, safety and the best formulation.