A castliner in the form of a three-dimensionally knitted sleeve comprises a microdenier yarn, and/or a spandex yarn, in particular, a spandex yarn having a flatter stress-strain curve than traditional spandex yarns. The use of the microdenier yarn contributes to the superior cushioning effect. The stretch and recovery properties of the particular spandex yarn contribute to superior fit and reduction of pressure points on the limb or body part to which the castliner is applied. Furthermore, the castliner is rendered water resistant and has significantly improved antimicrobial properties, both of which reduce incidents of skin irritation and unpleasant smell. As a result, the patient wearing the castliner of the invention is able to bathe and get wet without otherwise replacing the hard casting and castliner after such events.