A circular knitting machine for knitwear or hosiery, comprising: - a bearing structure; - at least a needle-bearing organ or needle cylinder rotatably mounted in the bearing structure; - a plurality of needles supported by the needle-bearing organ and mobile so as to produce a knitted fabric; wherein a plurality of flanked stitch-forming slots is defined in an external surface of the needle-bearing organ, each of which slots being open at least at a respective upper end and configured for movably housing at least a portion of a respective needle actuable with alternating motion along the stitch-forming slot with an extracting motion, by means of which the needle is extracted with the tip thereof and with a portion of a stem thereof superiorly from the needle-bearing organ through the upper end of the relative stitch-forming slot in order to operate an unloading, on the stem thereof, of a knit loop previously formed and/or to operate a collecting of the thread or the threads dispensed at a thread feeder of the machine, and with a return motion, by means of which the needle is returned with the tip thereof into the relative stitch-forming slot so as to form a new knit loop, actuating the knock over of the knit loop previously formed in order to produce a knitting stitch, wherein the needle-bearing organ is superiorly provided with a knit-forming plane destined to restingly receive portions of knitting situated between two contiguous needles while the needles, after having collected the thread at a thread feeder of the machine, return into the respective stitch-forming slots of the needle-bearing organ in order to form a new knit loop and to knock over the previously-formed knit loop, the stitch-forming slots being superiorly open on a side of the needle-bearing organ where the knit-forming plane is defined, the knitting machine comprising, in at least a part of the zones of the needle-bearing organ comprised between two contiguous stitch-forming slots, retaining organs of the knitting exhibiting each a respective portion defining an abutment shoulder for the knitting, each retaining organ of the knitting being mobile on command from a first position, in which it does not interfere with the knitting being formed, to a second position, in which it inserts, with the portion defining the abutment shoulder, between two contiguous needles, in a zone which superiorly faces the knit-forming plane, so as to retain the portion of knitting extending between two contiguous needles, opposing the dragging of the knitting along the needles during the extracting motion of the needles, the knitting machine comprising, for each of the retaining organs of the knitting, respective actuating means for commanding passage thereof between the first position and the second position in a coordinated way with the actuating of the contiguous needles, the machine further comprising, at least in the zones comprised between the contiguous stitch-forming slots provided with the retaining organ, lamellae defining the knitting plane each exhibiting a respective portion defining the knitting plane, each lamella being removably mountable to the needle-bearing organ, in such a way as to be positioned, in the zone between two contiguous stitch-forming slots, substantially coplanarly to the corresponding retaining organ located in the zone, and in such a way that the respective knitting plane defining portion defines a respective portion (Px) of the stitch-forming plane of the needle-bearing organ, wherein each lamella is provided with a holding portion, configured for being externally facing the external surface of the needle-bearing organ in a respective zone between two adjacent stitch-forming slots, characterised in that each of the lamellae defining the knitting plane exhibits a respective mounting portion, configured for and predisposed to enabling single and removable mounting of the lamella to the needle-bearing organ, and wherein the knitting plane defining portion is interposed between and connects the mounting portion and the holding portion. - a bearing structure; - at least a needle-bearing organ or needle cylinder rotatably mounted in the bearing structure; - a plurality of needles supported by the needle-bearing organ and mobile so as to produce a knitted fabric;