## 4 Structure and Construction of Compression Orthopaedic Products
The option of introducing an elastomeric yarn into the knitted structure has a significant impact on its properties. Thus, introducing elastomeric yarns in the knitted structure in the form of inlay yarn makes it possible to create fabrics with greater elongation, elasticity and lower raw material consumption compared to other discussed methods. However, if the elastomeric yarn is knitted into the structure creating loops, it increases the reliability of its fastening in the structure and its stretchability in two directions. When making compression stump covers, the primary requirement is to create tactile comfort. Therefore, the single-knitted structure of single patterns is used for their manufacture. In this case, the elastomeric yarn, which provides compression, can be knitted into loops on all needles or partially, according to the pattern repeat, with the formation of floats in places where it is not knitted, and can also be introduced into the ground structure in the form of trucks or inlay yarns. Table 6 shows the knitting patterns that are used to make compression products of a given shape. \begin{table}
\begin{tabular}{l c} \hline \hline
**Group** & **Type of Knitting Pattern** \\ \hline \begin{tabular}{l} Medical orthopaedic \\ compression supports \\ \end{tabular}  & \ \begin{tabular}{l} - \\ - \\ - \\ - \\ \end{tabular}  &
\begin{tabular}{l} Double wet-knitted pattern with elastomeric inlay yarn; elastomeric yarn can also be laid as a fleece yarn by creating trucks and floats in turn. A higher level of compression is mainly achieved by increasing the thickness of the elastic core of the inlay yarn, although adjustments may also be made to the ground yarn [74; 85]. The weft inlay yarns can be inserted in every single course or certain courses according to a pattern [41; 86]. The level of compression is partially defined by inlay yarn properties, which are directly related to the modulus of elastic core yarn and the covering parameters. Regardless of the selected raw material of covering yarns, the tensile force of elastomeric inlay yarn exponentially increases by increasing elongation. In the area of low elongations (50% for elastomeric yarns), properties of inlay yarn's covering yarns do not have a significant influence on compression properties, whereas only elastomeric core yarn is affected by the tensile strength. It means that covering yarns may be chosen, depending on comfort, hygiene, aesthetic, etc., requirements [85]. The inlay yarn insertion density has a valuable influence on the generated compression. This influence has an exponential character. Up to 25% higher compression values were estimated in fruits with the inlay yarns inserted in every single course in comparison with the knits with twice lower inlay yarn insertion density but with the same total amount of the inlay yarns [41; 86; 87]. In order to design suitable orthopaedic compression support, the following parameters must be appropriately selected: the type and the linear density of the base yarn, the type and the linear density of elastomeric yarn, the knitting device (warp or weft, flat or circular) and its parameters (gauge, number of working needles or diameter of the cylinder, etc. ), knitting pattern and the main structural and technological parameters (loop length, loop density, density of laid-in elastomeric yarns, initial pre-tension of the elastomeric yarn, etc.) [88]. Orthopaedic supports may be knitted as seamless products or sewn from knitted and other materials (e.g., neoprene). Seamless products are usually designed for mass production, are produced of a few sizes and are usually used for prevention purposes. Sewn compression products may be produced by cutting out suitable blanks from planar material. The main disadvantage of this is the difficulty of achieving an exact anatomical fit of the bandages and a large number of connecting points, such as seams, are created.