Glucosamine and chondroitin sulfate are building blocks of normal cartilage. But studies don't agree on whether these supplements can help reduce pain or slow cartilage damage when you have osteoarthritis. Research is ongoing.
Your doctor may still recommend trying glucosamine, but if there's no obvious improvement in 3 months, you can stop taking it.
Since the goverment doesn't regulate supplments like drugs, choose products sold by large and well-established companies to assure that you get a consistent dose.