Patients with hip osteoarthritis (OA) show abnormal movement patterns, including the leaning of the trunk toward the affected limb (Duchenne limp). Patients with severe OA, especially those with OA due to hip dysplasia, show a lateral pelvic drop (Trendelenburg sign).
The aim of this preoperative study is to investigate the relationship between superior migration of the arthritic femoral head, pain, and hip abductor muscle strength, and to clarify the relationship between the coronal plane gait patterns with pain and hip abductor muscle strength.
The subjects of this study were 18 patients with unilateral hip OA secondary to dysplasia. A radiographic analysis was performed on standardised anteroposterior pelvis films. The abductor muscle strength of the OA hip joint was measured with a handheld dynamometer. The tilt angle of the pelvis and trunk lean angle during gait were obtained using a 3-dimensional motion analysis system. Visual analogue scale (VAS) of pain was obtained after trial.
The 2 lateral pelvic angle patterns at the mid-stance of the affected limb during gait were detected. 1 is a pattern that was pelvic rise, and the other was a contralateral pelvic drop. Subjects with pelvic drop showed more superior femoral migration than that with pelvic rise (r = 0.69 
The pelvic drop Trendelenburg sign was influenced by superior migration of the femoral head, whereas the trunk lean Duchenne limp was found to be affected by pain.