Kyocera ABS system, a ceramics-on-ceramics type hip prosthesis, has been prohibited due to consecutive accidents such as the dissociation of the UHMWPE liner and the fracture of the alumina inlay. It has been presumed that loosening of the locking system connecting the metal shell and the liner is the primary mechanism of the liner dissociation. In this study, the finite element analysis (FEA) of the ABS system was conducted to assess the loosening mechanism qualitatively and quantitatively. The FEA results showed that very high stress concentration was generated at the locking grooves of the liner, indicating severe damage was likely formed under high stress condition. The FEA including a damage model was also performed to simulate such damage formation at the locking grooves. The FEA result exhibited that the four grooves were severely damaged under tensile and compression loadings, resulting in the loosening of the locking system. It was thus confirmed that the dissociation of the liner was initiated by those damage formation at the grooves.