Addition of 17β-estradiol to dexamethasone-treated arthritic mice protects against osteoporosis induced by ovariectomy and arthritis. Female sham-operated (n = 12) or ovariectomy (OVX) mice treated with vehicle (Veh; n = 10), 17β-estradiol (E2; n = 10), dexamethasone (Dex; n = 9), or a combination of both Dex and E2 (n = 10) were used in order to evaluate the effects of treatment on arthritis and bone mineral density (BMD). Treatment was administered five days per week, starting after the first appearance of arthritis (day 23), and continued until the termination of the experiment (day 44). (a) Frequency and (b) severity of arthritis were evaluated every third day. Severity is expressed as the mean ± standard deviation in each group. (c) Histologic scores of destruction in paw sections. (d) Trabecular BMD of one femur. Scatter plots represent scores of individual mice, and bars show the median in each group. The non-parametric Kruskall-Wallis test with post hoc comparison was used for statistical evaluation of all parameters, *P<0.05, **P<0.01, ***P<0.001.