Symptomatic slow-acting drugs for osteoarthritis (SySADOAs) are a class of drugs characterized by a slow-acting and prolonged symptomatic effect on osteoarthritis (OA), reducing pain and improving the functional status. They include chondroitin (sulfated or not), diacerein, glucosamine (sulfated or not), avocado-soybean unsaponifiables, and intra-articular hyaluronic acids. These medicines have been widely copied, and today, many different preparations marketed as “dietary supplements” or “nutraceuticals” are available for each of them on the OA and joint health market. These over-the-counter products vary significantly in their extraction methods and purification techniques, resulting in notable differences in content, composition, purity, bioavailability, biological effects, and safety. Besides, there is a wide disparity regarding the regulatory and quality standards for dietary supplements, as well as the compliance with these standards from one country to another, even within the European Union. There is no control of the quantities/doses of the various components in end-product supplements. This contrasts with the strict standards and quality controls that accompany and govern the manufacturing and composition of pharmaceutical preparation. The aim of this literature review was therefore to compare SySADOAs and dietary supplements/nutraceuticals for AO, particularly in terms of composition, efficacy, safety and tolerance. Our conclusion based on available evidence is that practitioners should be careful in using dietary supplements and should prefer prescribing or recommending SySADOAs of pharmaceutical grade in the management of OA.