In this issue of Arthritis Care & Research, we present the tenth in a series of themed issues, which are highly relevant to rheumatologic practice and clinical study. These themed issues, which appear once or twice a year, are designed to highlight state-of-the-art information in the field of rheumatology. The topic for this themed issue is muscle and bone issues in relation to outcomes in the rheumatic diseases. Sarcopenia, muscle volume loss, inflammation, muscle fat infiltration, muscle power, physical limitations, and exercise interventions are among the topics submitted for this themed issue of the Journal. A solicitation for manuscripts for the next theme, concerning obesity issues and outcomes in the rheumatic diseases, has been announced in the Journal. The manuscripts submitted for the themed issues navigate the same peer-review process of Arthritis Care & Research as do all scientific manuscripts, and therefore meet the same rigorous standards as articles in this or any other issue.

Over past decades, muscle, fat, and bone have taken a back seat to singular measures of disease activity and a more monocular vision of the impact of rheumatic disease upon muscle and physical function. The 21st century has brought a renewed scientific interest in the role of muscle and bone in the pathogenesis and measurement of the impact of the rheumatic diseases as well as their outcomes. Our understanding of sarcopenia, an ill-defined but well-appreciated clinical entity related to many rheumatic diseases is on the verge of important bench science and clinical breakthroughs. The impact of fractures in children treated for rheumatic disease is increasingly appreciated and evaluated for early intervention. The integration of the role of muscle, fat, and bone in many chronic diseases and their treatments is of great concern to clinicians as well as patients with rheumatic diseases.

The call for papers for this theme issue resulted in more than 50 submissions; from among these, we are proud to publish 18 manuscripts covering important aspects of muscle, fat, and/or bone in the rheumatic diseases, including osteoarthritis, rheumatoid arthritis, systemic lupus erythematosus, osteoporosis, and ankylosing spondylitis. Theses manuscripts include review articles on bone outcomes in persons with systemic lupus erythematosus, fatty infiltration and muscle atrophy resulting from rotator cuff tears, and hereditary hemochromatosis, as well as original articles documenting the longitudinal changes observed in intermuscular fat volume and quadriceps muscle volume, the influence of osteoarthritis upon sarcopenia, body composition and physical functioning, and muscle quality and strength using both randomized and observational study designs.

These papers are intended to spark intellectual curiosity and generate interest in a more systematic evaluation of the role that muscle and bone display in the pathophysiology of and outcomes in the rheumatic diseases as our understanding of the components and their synergies in the rheumatic diseases come under greater scrutiny in the years ahead.