Pain is a common problem for patients undergoing radiation therapy, exacerbated by inconsistent pain documentation. Free-form templates, pain score prompts, and forcing functions are a hierarchy of constraint systems that can be applied to data entry. This study assessed the impact of incorporating these models into electronic health records on pain documentation rates during 450 on-treatment visits and pain severity of 258 patients with bone metastases and breast and thoracic cancer during radiation therapy. Pain documentation is associated with more robust constraint systems: free form (0.11, 95% CI [0.07, 0.18]), pain score prompts (0.87, 95% CI [0.81, 0.92]), and forcing functions (0.97, 95% CI [0.93, 0.99]). Forcing functions also were associated with improved pain control over the course of radiation treatment for bone metastases compared with pain score prompts ( P = .026, nonparametric Kruskal-Wallis). Use of forcing functions correlates with increased pain documentation rates, which contributes to improved pain management.