Analysis of the kinematic features of pelvic and lower limb motion in patients with hip osteoarthritis and acetabular dysplasia

Patients with acetabular dysplasia frequently develop early-onset osteoarthritis due to insufficient femoral head coverage and hip instability, leading to compensatory gait adaptation. This study aimed to elucidate three-dimensional gait kinematics of the pelvis and lower limbs in these patients by analyzing the peak range of motion, as well as the timing and duration of joint movement throughout the gait cycle, using statistical parametric mapping. We examined 25 patients with acetabular dysplasia (mean age: 27.4 years) and compared them with 25 healthy controls (mean age: 29.4 years). Gait was assessed using a motion capture system, and pelvis and lower-limb joint angles (hip, knee, and ankle) in the sagittal and coronal planes were evaluated using a rigid-body model. Compared with controls, patients exhibited increased anterior pelvic tilt, reduced pelvic hike on the non-weight-bearing side, decreased hip extension, and increased hip and knee flexion. Ankle motion showed reduced plantarflexion and significantly increased eversion. These findings highlight characteristic compensatory gait patterns in acetabular dysplasia, especially involving pelvic and ankle movements. Understanding kinematic adaptations may facilitate effective surgical planning and postoperative rehabilitation protocols to improve functional outcomes.