Indexes for objectively evaluating abnormal gait in hip osteoarthritis (OA) patients and determining effective interventions are unclear. We analyzed the abnormal gait of hip OA patients by focusing on movements of the trunk and pelvis to establish an effective evaluation index for each direction of motion. We studied 28 patients with secondary hip OA due to developmental dysplasia of the hip and 16 controls. The trunk and pelvic movements during gait were measured in the medial-lateral (x), vertical (y), and back-and-forth (z) directions by a triaxial angular accelerometer. Gait speed, steps, step length, muscle strength, range of motion, and timed up-and-go (TUG) test performance were measured. We determined the correlations between physical function and the index of abnormal gait in the hip OA patients. Movements other than trunk and pelvic motions in the y-direction indicated abnormal gait in the patients. Significant correlations were found between abnormal gait and range of motions (extension, internal rotation), TUG score, stride length, and steps. The TUG test, stride length and steps were important for evaluating abnormal gait in hip OA patients. Individual interventions for each movement direction are required.