Functional assessments of the meniscus assists to diagnose diseases of the knee joint. To estimate the degree of the degeneration of the injured meniscus, this paper proposes an automated method for segmenting the region of the meniscus from multidetector computed tomography (MDCT) images. The novel feature of the proposed method is that we segment the meniscus based on a fuzzy rule-based representative line finding algorithm. The representative line, which is a new concept, is a line that abstracts the position and shape of the meniscus. Experimental results on the extended and flexed knee joints for three healthy subjects show that our method found a proper representative line, and segmented the meniscus successfully.