The kinematic effects of three quarter and full length foot orthoses on anterior knee pain sufferers when walking and descending stairs

Abstract

Background: Patellofemoral pain is a common disorder whose aetiology is complex often being described as multifactorial, increased load of the patellofemoral joint is often attributed to foot function. Foot orthoses are commonly prescribed for this condition; however the mechanisms by which they work are poorly understood. Previous studies using single segment foot models have hypothesised that it may be control of the midfoot which hold the key to understanding orthotic control. Over the last decade biomechanical analyses has advanced so it has become possible to divide the foot into segments, however no previous studies have investigated the use of orthoses on different segments of the foot when shod.
The overall aim of this study was to investigate the differences seen in the kinematics and kinetics of the lower limb between a patellofemoral pain group and a group of normals when using a standardised orthosis prescription during walking and descending a step.
Method: Initially fifteen healthy subjects had foot orthoses moulded to their feet, they were asked to walk at a self-selected pace and complete a 20cm step down; comparisons were made between sandals and shoes, plus two different orthoses. Kinematic and kinetic data were recorded using 10 Oqus cameras and 4 AMTI force platforms. The shoe data from the 15 healthy subjects was re-analysed and used as a control group to compare against 15 subjects diagnosed with patellofemoral pain. The foot was modelled using the calibrated anatomical systems technique (CAST) fixing the marker set directly on the feet and shoes of normal subjects which permitted comparisons of excursions between the shoes and sandals and the effects of the orthoses.
Results 1: Similar changes in the pattern of movement were seen between the shoe and the sandals conditions with and without the orthoses; the shoes reduced the excursions recorded except the transverse plane of the rearfoot. At the knee maximum extension was increased and maximum flexion at toe off was reduced by the orthoses.
Initial Conclusions: Expectedly the shoes reduced the range of motion over the sandal condition in most planes; however the similar effects seen with the orthoses in both types of footwear suggesting it was acceptable to use shoes in the later study.
Results 2: Significant differences were seen between the healthy subjects and the patellofemoral pain subjects at the foot and the knee. Both orthoses produced statistically significant results at the foot. In addition there was a significant reduction in the knee coronal plane moment range during the forward continuum phase of step down; this was attributed to a change in the ground reaction force as there were no changes reported in the kinematics of the knee.
Conclusions: The method of placement of the markers was able to detect small changes within the foot segments. This study identified potentially important differences between the patellofemoral pain subjects and the normals in both the knee and foot segments. However due to the lack of pain during the walking and step down trials it could not be determined if the changes were due to pain avoidance mechanisms or if they were causative factors. Many of the changes produced by the orthoses tended to be local to the foot, except for the knee coronal plane moment range during the forward continuum phase of step down. To the authors knowledge this work is unique in its investigation of the motion of foot segments while shod and confirmed the clinically held belief it is essential to consider footwear when prescribing orthoses to patients. The use of foot mechanics could be of interest to further research and may help to define sub-populations within this condition.