Supplementation with l-arginine, an amino acid naturally found in many protein-rich foods, has previously been shown to alleviate experimental arthritis, but its influence on inflammatory bone loss and the underlying mechanisms were unclear. New research now shows that l-arginine inhibits arthritis, inflammatory osteoclastogenesis and inflammation-mediated bone loss by reprogramming amino acid metabolism in osteoclasts, and suggests that therapeutic l-arginine supplementation could offer a way to inhibit inflammation in arthritis and provide protection against inflammatory bone loss.