On-line system verification requires the efficient reconstruction of the state space a model checker generates. This paper proposes an approach to reconstruct the current state of models of real-time systems, implements it in the Uppsala and Aalborg model checker (UPPAAL) and thus renders on-line model checking in UPPAAL possible. On-line model-checking can be employed if parameters of models need to be adjusted to real-world values in case models are inaccurate. Applications include closed-loop patient monitoring and care taking as patient models commonly fail to accurately model all interactions in the human body and thus cannot provide good long-term estimates to ensure the patient's safety. We exploit use-definition chains in state space transformations to reduce the amount of reconstruction transformations. During testing the method reduced the amount of transformations by 42% on average over all experiments.