April 2015

Inclination insights: Ankle motion predicts wedge insole effect

In the moment: Knee OA

4ITM-OA-illustrationBy Larry Hand

Motion analysis of the ankle joint complex may predict how a patient with medial knee osteoarthritis (OA) will respond to using a lateral wedge insole, according to a new study from the University of Salford in the UK.

The investigation, an ancillary study to a larger ongoing clinical trial, included 70 individuals (27 women) who had experienced unilateral medial knee pain while walking on a flat surface within the previous week. They were aged an average of 60.3 years and an average body mass index of 30.5 kg/m2. Individuals with radiographic information available had an average Kellgren-Lawrence severity score of 2.63.

Researchers used a 16-camera 3D motion analysis system and a force plate to assess the participants as they walked while wearing a shoe with a lateral wedge insole on the affected side and while wearing shoes only. The ethylene vinyl acetate lateral wedge insoles extended from the heel post to the fifth metatarsal head and did not include medial arch support. All participants wore flat, thin-soled leather shoes.

“We used a five-degree lateral wedge, as this fits within the patient’s shoes comfortably and has been shown in previous research by us to reduce medial knee loading in patients with medial knee osteoarthritis,” first author Graham J. Chapman, PhD, a research fellow in knee biomechanics and injury at the University of Salford, told LER by email.

Participants varied considerably in response to wearing the shoe with the wedge insole. Of the 70 individuals, 23 experienced a mean 8.5% increase in external knee adduction moment (EKAM) when wearing the insole. The remaining 47 individuals experienced a mean 11.39% reduction in EKAM. Ankle angle at peak EKAM and peak eversion ankle/subtalar joint complex angle in the control position predicted if using a lateral wedge insole was likely to be associated with a decrease in EKAM. The researchers did not test for the effect of radiographic severity, foot type, or pain and discomfort.

“The finding that people with a more everted foot when walking in the control condition were more likely to reduce their knee loading when wearing lateral wedge insoles was slightly surprising,” Graham said.

The findings, epublished in March by Osteoarthritis & Cartilage, represent a first step that researchers hope will lead to clinical algorithms for matching subgroups of knee OA patients with treatments that are most likely to be effective.

“This is only the beginning for this area of work,” said senior author and principal investigator Richard K. Jones, PhD, who is a professor in clinical biomechanics at the university. “More research is required to understand the role of the foot and ankle in knee loading and medial knee osteoarthritis in order to improve the clinical outcomes for patients suffering with this disease and to determine biomechanical response in these interventions.”

Ryan Lewinson, who has studied the effects of wedged insoles as an MD/PhD student at the University of Calgary in Alberta, Canada, concurred with the UK researchers’ acknowledgment that 3D gait analysis systems are currently too expensive and time consuming to be used regularly by most clinicians.

“Evaluation of the peak knee adduction moment and other associated biomechanical variables are likely to remain, for the most part, exclusive to research-based settings over the next few years,” Lewinson said. “The next step is to identify methods that predict response to wedged insoles, but in clinical settings without three-dimensional gait analysis systems.”

Peter Barrance, PhD, a senior research scientist at Kessler Foundation in West Orange, NJ, who has also studied the effects of lateral heel wedging, agreed. “It will be important to also understand whether, in addition to the types of dynamic measures available in laboratory-based gait analysis, clinical measurements of standing ankle angulation can be used to help predict treatment efficacy,” Barrance said.


Chapman GJ, Parkes MJ, Forsythe L, et al. Ankle motion influences the external knee adduction moment and may pre- dict who will respond to lateral wedge insoles: An ancillary analysis from the SILK trial. Osteoarthritis Cartilage 2015 Mar 5. [Epub ahead of print]

Jones RK, Zhang M, Laxton P, et al. The biomechanical effects of a new design of lateral wedge insole on the knee and ankle during walking. Hum Mov Sci 2013;32(4):596-604.

Jones RK, Chapman GJ, Forsythe L, et al. The relationship between reductions in knee loading and immediate pain re- sponse whilst wearing lateral wedged insoles in knee arthritis. J Orthop Res 2014;32(9):1147-1154.

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