Objective. Mice with progressive ankylosis, a spontaneous arthropathy, were treated with phosphocitrate (PC) in vivo to determine the effect of PC on disease progression. Methods. Two groups of mice with progressive ankylosis (matched for age, weight, and sex) were treated parenterally for 6 weeks with either PC or saline vehicle. Results. Clinically, histologically, and microradiographically, there were significant differences in disease progression and severity in the PC‐treated and the saline‐treated mice. Conclusion. PC appears to inhibit disease progression in murine progressive ankylosis.