Dynamic Measurement Modeling (DMM) is a psychometric paradigm that uses longitudinal data to estimate students' capacity to learn over the course of an educational program (i.e., growth scores). Here, we provide justification for this approach in health professions education and demonstrate its proof of concept with three time-points of USMLE Step Exams to generate growth scores for 454 current and recent medical-learners. We demonstrate that learners vary substantially on their growth scores, and those growth scores have strong reliability. Growth scores were significantly and positively predicted by indicators of medical learner readiness (e.g., undergraduate GPA and MCAT scores). Growth scores were also capable of significantly and positively predicting future ratings of clinical competencies during internship (e.g., Patient Care, Interpersonal Skills).