Natural Joint Support Plus Antioxidants. Supports Healthy Joints and Flexibility. Helps Maintain Joint Mobility. Connective Tissue Support. Supports Joint Tissue Health. Healthy joints, Happy pets. Gluten free. K9 Joint Strong is designed to provide dual benefits joint factors and antioxidants. Joint factors include USP-standardized glucosamine, MSM and others to help maintain normal joint function. In addition, natural antioxidant help protect cells (including joint) from free radical damage. This two-way joint support health strategy is meant to help maintain joint mobility. Antioxidant protection, supports connective tissue health, assists in combating environmental pollutants, supports healthy joints.