The effect of foot orthoses on movement patterns during walking and stair decent in normal subjects and patellofemoral pain patients

Abstract

Background: Patellofemoral pain is a common disorder whose aetiology is complex often being described as multifactorial. It has been suggested that an increased load of the patellofemoral joint could be attributed to foot function and that foot orthoses could be used as a treatment for patellofemoral pain. However, the mechanisms by which foot orthoses work is poorly understood. Therefore there is still a need to develop an understanding of exactly how foot function and foot orthoses affect knee function in patients with patellofemoral pain.

Purpose: The aim of this study was to firstly determine if clinically important differences exist in knee kinematics and kinetics between a group of subjects with patellofemoral pain and a group of normal subjects during walking and descending steps. Secondly the study aimed to explore if clinically important changes in foot and knee mechanics could be produced when using two standardised foot orthosis prescriptions.

Methods: Fifteen healthy subjects and fifteen subjects with a diagnosis of patellofemoral pain were recruited. All subjects had mild to moderate foot pronation as defined by a score of at least +6 on the foot posture index. All patellofemoral pain subjects scored 3 or more on the numeric pain rating scale when descending stairs. All subjects had ¾ and full length foot orthoses custom fabricated by using a pair of Slimflex™ insoles with a 5 degree medial EVA wedge. Subjects were asked to walk at a self-selected pace and complete a 20 cm step down using the two different orthoses. Kinematic and kinetic data were recorded using 10 Oqus cameras and 4 AMTI force platforms. Reflective markers were placed on the foot, shank and thigh using the Calibrated Anatomical Systems Technique. In addition the patellofemoral pain subjects were ask to rate their pain during the tests.

Results: Significant differences were seen between the healthy subjects and patellofemoral pain subjects during both tasks. This included: movement at the midfoot and rearfoot in flexion/extension and inversion/eversion (p = 0.003 to 0.016); movement of the knee joint into flexion, adduction and external rotation (p = 0.003 to 0.016); and in ankle and knee joints moments in dorsiflexion/flexion and adduction (p = 0.012 to 0.035). The foot orthoses produced statistically significant differences in the movement in the forefoot, midfoot and rearfoot across all three planes for both tasks (p = 0.001 to 0.032). The foot orthoses showed no change in the knee kinematics, however both the ¾ and full length foot orthoses produced a significant reduction in the knee adduction moments during step descent (p = 0.019, p = 0.028).

Conclusion(s): This study identified potentially clinically important differences between the patellofemoral pain subjects and the normal subjects in the knee mechanics during walking and step down. The foot orthoses also reduced the coronal plane knee moment during the forward continuum phase during step down, which can be associated with a reduction in the medial/lateral loads on the knee joint.