The Force Concept Inventory (FCI) can serve as a summative assessment of students' conceptual knowledge at the end of introductory physics, but previous work has suggested that the knowledge measured by this instrument is not a unitary construct. In this article, we consider the idea that FCI performance may reflect a number of student attributes including relational knowledge structures of physics concepts, expert-like attitudes, and problem-solving skills. Using a large calculus-based introductory physics course, we show that knowledge of conceptual relationships (i.e., knowledge structures), attitudinal measures, and problem-solving ability are all measures that uniquely contribute to a postinstruction FCI score. While these associations do not reveal the nature of their relation to the FCI (it could be that good students perform well on all these measures), they do provide evidence that improving any one of these aspects may improve a student's overall FCI score.