Baby Boomers and others with aching knees take note: Several companies are selling drinks fortified with glucosamine, a nutrient believed to promote joint health. Joint Juice Fitness contains 1500 mg of glucosamine, while Elations delivers the same plus 1200 mg of chondroitin (often used along with glucosamine). Not to be outdone, Minute Maid is selling Active Enhanced Orange Juice, with 750 mg of glucosamine per 8 ounce serving.