An article of apparel including a tubular knit textile region is provided, as well as an apparel printing system for printing on regions of the tubular knit textile region and related methods. The article of apparel can include a tubular knit textile region having an internal side and an opposite external side configured to be exposed during use, a plurality of yarns in an arrangement of interlocked loops forming parallel rows and channels therebetween, and a printed ink design on its external side. The printed ink design can be formed from ink applied to the parallel rows of loops and to the channels. An apparel printing system for printing on the article of apparel can include a textile printer having a print head and a tubular platen that includes features on the platen surface to retain and register the tubular knit textile on the platen surface during printing.