Linear regression analyses of serum cytokines versus local bone loss or local inflammation. (a) to (d) Bone loss was quantified as the percentage change in areal bone mineral density (BMD) from the day of onset for clinical arthritis (day 0) to day 14 post onset. (e) and (f) Paw swelling was quantified as the percentage change from day 4 post onset (treatment initiation) to day 14 post onset. Serum receptor activator of NF-κB ligand (RANKL) and IL-1β were evaluated on day 14 post onset. Open circles, nonarthritic controls + vehicle; black circles, arthritis + vehicle; open triangles, arthritis + IL-1 receptor antagonist; grey diamonds, arthritis + PEGylated soluble TNF receptor type I; grey circles, arthritis + OPG-Fc. n = 8/group. AIA, adjuvant-induced arthritis; CIA, collagen-induced arthritis.