Original article
Biomechanical and Clinical Outcomes With Shock-Absorbing Insoles in Patients With Knee Osteoarthritis: Immediate Effects and Changes After 1 Month of Wear

https://doi.org/10.1016/j.apmr.2011.09.019Get rights and content

Abstract

Turpin KM, De Vincenzo A, Apps AM, Cooney T, MacKenzie MD, Chang R, Hunt MA. Biomechanical and clinical outcomes with shock-absorbing insoles in patients with knee osteoarthritis: immediate effects and changes after 1 month of wear.

Objectives

To examine the effectiveness of shock-absorbing insoles in the immediate reduction of knee joint load, as well as reductions in knee joint load, pain, and dysfunction after 1 month of wear, in individuals with knee osteoarthritis (OA).

Design

Pre-post design with participants exposed to 2 conditions (normal footwear, shock-absorbing insoles) with a 1-month follow-up.

Setting

University laboratory for testing and general community for intervention.

Participants

Community-dwelling individuals (N=16; 6 men, 10 women) with medial compartment knee OA.

Intervention

Participants were provided with sulcus length shock-absorbing insoles to be inserted into their everyday shoes.

Main Outcome Measures

Primary outcome measures included the peak, early stance peak, and late stance peak external knee adduction moment (KAM); the KAM impulse (positive area under the KAM curve); and peak tibial vertical acceleration. Secondary outcomes included walking pain, the Western Ontario and McMaster Universities Osteoarthritis Index pain subscale and total score, and a timed stair climb task.

Results

There was a significant reduction in the late stance peak KAM with shock-absorbing insoles (P=.03) during follow-up compared with the baseline test session. No other immediate or longitudinal significant changes (P>.05) in the other KAM parameters or peak tibial acceleration after use of a shock-absorbing insole were observed. However, significant improvements in all measures of pain and function (P<.05) were observed.

Conclusions

Shock-absorbing insoles produced significant reductions in self-reported knee joint pain and physical dysfunction with 1 month of wear in patients with knee OA despite no consistent changes in knee joint load. Further research using randomized controlled trials, with larger sample sizes and explorations into long-term use of shock-absorbing insoles and their effect on disease progression, is warranted.

Section snippets

Participants

Individuals with medial compartment knee OA were recruited from the community via advertisements in local newspapers. Inclusion criteria consisted of radiographic evidence of knee OA (Kellgren & Lawrence [KL] grade 2 or greater)27 as determined from standing short-film posteroanterior radiographs, and varus malalignment as measured from the short-film posteroanterior radiographs and using published regression equations to calculate the mechanical axis of the lower limb.28 All subjects had knee

Results

A total of 16 participants (10 women) with a mean age ± SD of 66.9±12.5 years, body mass index of 27.7±7.3kg/m2, and radiographic lower limb alignment of 178.0°±3.7°—indicative of varus malalignment—were recruited. Ten participants had mild knee OA (KL grade 2), 2 had moderate knee OA (KL grade 3), and 4 had severe knee OA (KL grade 4) in the medial compartment of the tibiofemoral joint. Fourteen participants (88%) returned for follow-up testing, a mean ± SD of 30.9±3.9 days after the baseline

Discussion

Findings from the present study suggest that shock-absorbing insoles can produce significant improvements in knee joint pain and physical function after 1 month of wear. However, the role of biomechanics in improvements in clinical measures is unclear based on our data. Although a significant reduction was observed for the late stance KAM peak (KAM2), no significant reductions were found in any other measure of knee joint loading during walking. Given that previous research has demonstrated

Conclusions

Shock-absorbing insoles can significantly improve measures of knee joint pain and physical dysfunction after 1 month of wear in patients with knee OA. Although these results may not have been the result of altered lower limb biomechanics during walking, there is now evidence for the role of shock-absorbing insoles in the clinical self-management of this disease. Indeed, shock-absorbing insoles represent an intervention that is inexpensive and noninvasive and has minimal side effects for

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    Supported in part by a research grant from The Arthritis Society/Arthritis Health Professions Association.

    No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated.

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