Life cycle assessment (LCA) research on the performance of circular economy (CE) measures such as reuse, repair and remanufacturing has been criticized for inadequate consideration of functional equivalency of circular compared to new products, allocation between use phases, displacement rates, rebound effects, product use and user behavior. For such reasons, it has been argued that our understanding of the environmental performance of CE is poor and over-optimistic. Motivated by these criticisms, this paper presents an outline of a conceptual framework developed to improve CE LCA research. The framework was developed through literature review, workshops and ongoing CE LCAs in the sport and outdoor sector. The paper overviews challenges related to mentioned criticisms and possible approaches to addressing them, presents a model for how aspects influential to CE LCA results interrelate, and, proposes a structure for describing product-user life cycles more accurately. The outlined conceptual framework could be an important step towards improving CE LCAs and, ultimately, our understanding of environmental outcomes of CE.