We address the problem of sorting the top-k elements of a set, given a predefined partial order over the set elements. Our means to obtain missing order information is via a comparison operator that interacts with a crowd of domain experts to determine the order between two unordered items. The practical motivation for studying this problem is the common scenario where elements cannot be easily compared by machines and thus human experts are harnessed for this task. As some initial partial order is given, our goal is to optimally exploit it in order to minimize the domain experts work.