Ligamentum cruciatum anterior ruptures are one of the most important causes of lameness in the hind legs of cats and dogs. Researchers have noted that conservative treatment may give positive results in dogs weighing less than 15 kg, but adequate operative intervention is required in older dogs with large body. For intraarticular and extraarticular surgery, various techniques have been described in which different autografts, allografts and synthetic materials are used. A rupture at ligamentum cruciatum anterior was detected in a 4 months old Tabby cat which was brought to Firat University Animal Hospital Surgery Department with sudden onset of lameness complaint. In this study, a line was used as synthetic material. The strength of the fishline used as a synthetic material has been favored because of its durability and its inert property. The subject of this study includes clinical, radiographic and ultrasonographic diagnosis of rupture at ligamentum cruciatum anterior in cat and used synthetic material in order to function as anterior cruciate ligament.