KER-Flex - Oral Joint Supplement Joint problems can be a limiting factor in a horse’s career. Therefore, care and maintenance of joints is a major concern. At Kentucky Equine Research (KER), we have studied joint health and the management steps necessary to minimize problems. KER-Flex, a new oral joint supplement developed by KER, is suitable for all classes of horses engaged in various types of exercise. KER-Flex contains a synergistic blend of glucosamine HCl, chondroitin sulfate, MSM and hyaluronic acid to provide broad-spectrum support of joint health.