The long-term unsatisfactory results and lack of confidence concerning biological cruciate reconstructions (see Chap. I.5) and especially the goal of reducing operative trauma and physiological disorders have led to the use of an alloplastic ligament in all cases of acute and chronic cruciate ligament tears. The synthetic ligament, implanted since 1980 without any change in its structure, is a 8-mm-wide and 1-mm-thick ligament of polyethylene terephthalate (Trevira-Hochfest 730) and meets all biological and material requirements suitable for cruciate ligament replacements [2, 3, 6–10]. The choice of this ligament followed the considerations and experiences discussed in Chaps. I.5 and II.5. Its biocompatibility has been confirmed by numerous tests and clinical follow-ups [1, 4–6, 10].