The reference posture used in angular motion calculations may play an important role in the relationship found between static posture and rearfoot motion in the frontal plane in a clinical population such as patients with patellofemoral pain syndrome. This study examined the relationship between rearfoot inversion and eversion during the stance phase of walking and the static relaxed standing measurement in women (aged 18 years and older) with patellofemoral pain syndrome and controls and examined the influence of the reference posture used when calculating dynamic motion. Two reference postures were investigated: vertical alignment between the rearfoot and the lower leg and relaxed calcaneal standing. When using the latter reference posture, a significant correlation was found between the static relaxed standing measurement and peak eversion in controls only. When using the vertical alignment reference posture, significant correlation was found only in the patellofemoral pain syndrome group for peak eversion and inversion. The positive relationship found in the patellofemoral pain syndrome group between dynamic angular measures, based on a neutral reference posture, and static relaxed standing indicated that for subjects with patellofemoral pain syndrome, the clinical rearfoot measurement of relaxed standing can be used to explain the pattern of rearfoot motion during walking.