Doctor's Best Glucosamine Chondroitin MSM provides three important nutrients which help support healthy joints and connective tissues: glucosamine, chondroitin and Methylsulfonylmethane (MSM, from OptiMSM). Glucosamine sulfate helps joint health for joint lubrication, better joint movement and flexibility. Cartilage, composed of proteoglycans, is mainly located on bones, near the joints and consists primarily of collagen protein with side chains called chondroitin sulfate. MSM supplies bioavailable sulfur needed to support joint health, hair, skin, and nails. OptiMSM is purified via distillation for highest purity and consistency and is an excellent source of bioavailable sulfur.