Knitting needles are the main elements for the knitting process and they are continuously in contact with fibers, yarns and contaminants existing in the structure of the yarns. In this study, the wear occurring inside latch needle hooks was examined empirically to explain how it is affected by the type of yarn and the machine parameters. The wear of the needle hook was represented numerically based on the technique of the comparison of local surface heights. Scanning electron microscopy (SEM) stereoscopy was used for the evaluation of the hook surfaces. The average surface roughness parameter (Ra) was utilized for evaluating the wear inside the needle hooks, depending on various machine parameters such as yarn tension, knitting speed, etc., and on various yarn properties such as fiber type and yarn type. The results of this study showed that SEM stereoscopy can be used to understand the wear mechanism of the surfaces of needles. Both the statistical analysis of Ra measurements and SEM images supported the results.