rib

A rib is a continuous raised ridge that runs lengthwise in knitted fabric, created by alternating columns of knit and purl stitches. The knit stitches form the raised parts while the purl stitches sit between them, creating a pronounced vertical texture. This structure is deliberately engineered into the fabric during knitting to produce elasticity, shape retention, and a distinctive tactile finish.

The most common rib patterns are 1x1 (one knit stitch, one purl stitch), 2x2 (two knit, two purl), and 2x1 (two knit, one purl). These ratios define the width and prominence of the ridges. A 1x1 rib creates fine, tightly spaced ridges used in fitted garments like sweater cuffs and collar bands. Wider ratios like 2x2 produce bolder, more elastic fabric suitable for body panels that need stretch recovery. The gauge (stitches per inch) and yarn weight dramatically affect how pronounced the rib appears and how much lateral stretch it provides.

Ribs are standard in knitwear finishing because they naturally gather fabric and recover from stretching better than plain stockinette stitch. A ribbed cuff on a sweater or trouser leg holds its shape after repeated donning and washings. Thermal undergarments and athletic wear often use ribs to anchor fabric to the body without binding. In flat knit production, ribs run perpendicular to the selvedge; in circular knit operations, they spiral continuously around the tube.

Problems in rib production include rib curl, where edges curl inward due to the tension differential between knit and purl columns, and rib imbalance, where one set of ridges becomes looser or tighter than the other due to machine tension drift or worn needle beds. Runs (dropped stitches) in ribs are especially visible because they break the regular pattern across the width of the ridge. Moisture content also matters: if yarn is too dry, ribs become brittle and prone to cracking during finishing processes.

The term rib likely derives from its visual resemblance to skeletal ribs: raised parallel structures with valleys between. In trade usage, ribbing is applied not only to finished garments but also to intermediate components sold to cut-and-sew manufacturers. Machine knit ribbing for sleeves, waistbands, and cuffs is often produced on dedicated rib looms, then packaged and shipped separately to assembly facilities.