Elsevier

Clinical Biomechanics

Volume 17, Issue 8, October 2002, Pages 603-610
Clinical Biomechanics

Static and dynamic biomechanics of foot orthoses in people with medial compartment knee osteoarthritis

https://doi.org/10.1016/S0268-0033(02)00073-6Get rights and content

Abstract

Objective. Gait biomechanics (knee adduction moment, center of pressure) and static alignment were investigated to determine the mechanical effect of foot orthoses in people with medial compartment knee osteoarthritis.

Design. Repeated measures design in which subjects were exposed to three conditions (normal footwear, heel wedge and orthosis) in random order.

Background. The knee adduction moment is an indirect measure of medial compartment loading. It was hypothesized that the use of a 5° valgus wedge and 5° valgus modified orthosis would shift the center of pressure laterally during walking, thereby decreasing the adduction moment arm and the adduction moment.

Methods. Peak knee adduction moment and center of pressure excursion were obtained in nine subjects with medial compartment knee OA during level walking using an optoelectric system and force plate. Static radiographs were taken in 12 subjects using precision radiographs.

Results. There was no difference between conditions in static alignment, the peak adduction moment or excursion of the center of pressure in the medial-lateral direction. No relationship was found between the adduction moment and center of pressure excursion in the medial-lateral plane. The displacement of the center of pressure in the anterior–posterior direction, measured relative to the laboratory coordinate system, was decreased with the orthosis compared to the control condition (P=0.036) and this measure was correlated with the adduction moment (r=0.45, P=0.019).

Conclusions. The proposed mechanism was not supported by the findings. The reduction in the center of pressure excursion in the anterior–posterior direction suggests that foot positioning was altered, possibly to a toe-out position, while subjects wore the orthoses. Based on the current findings, we hypothesize that toe-out positioning may reduce medial joint load.
Relevance

Knee Osteoarthritis is the most common cause of chronic disability amongst seniors. Developing inexpensive, non-invasive treatment strategies for this large population has potential to impact health care costs, quality of life and clinical outcomes.

Introduction

In knee osteoarthritis (OA), a common musculoskeletal disorder associated with aging [1], [2], the medial compartment is more commonly affected because it carries higher loads [3], [4]. In the healthy knee, between 71% and 91% of total joint load is transmitted through the medial tibiofemoral compartment [5], [6], [7] compared to 100% in the OA knee [8], [9]. Treatment strategies for the knee OA population aim to minimize the forces on the medial compartment [10], [11]. For example, a high tibial osteotomy (HTO) alters static lower extremity alignment thereby decreasing medial compartment loading. As well, conservative treatment strategies, such as knee braces and valgus heel wedges, affect lower limb mechanics and attempt to reduce medial compartment loading.

Subjective reports of decreased pain and improved function, particularly during walking, in patients with mild to moderate medial compartment knee OA have been observed with the use of a valgus heel wedge [12], [13], [14]. This treatment has reduced the need for pain medication [15], altered lower limb alignment [13] and in a young healthy population it reduced the knee's adduction moment [16]. While the alteration in limb alignment may alter the knee joint load, the relationship between static alignment and dynamic loading of the medial compartment remains equivocal [17], [18], [19]. On the other hand, since direct measurement of medial compartment loading is difficult, the knee adduction moment serves as an indirect measure of the load [6], [17], [18] such that a change in the adduction moment signifies a change in load distribution across the knee joint. Even considering the effects on alignment and the adduction moment, the above studies did not propose a mechanism for the dynamic effect a valgus heel wedge would have on the mechanics of level walking in the OA knee population.

The purpose of this study was to determine the immediate mechanical effect of a 5° valgus heel wedge and a modified orthosis, where the lateral aspect of the rearfoot is raised into a 5° valgus position, on the peak knee adduction moment (PAM) and displacement of center of pressure during level walking in the OA knee population. Specifically, it was hypothesized that valgus heel wedges and modified orthoses would shift the center of pressure laterally on the foot during level walking, reducing the moment arm of the adduction moment in the frontal plane, thereby resulting in a decrease in the knee adduction moment (Fig. 1). Secondly, the effect of the interventions on static lower limb alignment was investigated.

Section snippets

Research design & study participants

The study was a single visit, repeated measures design in which subjects were exposed to three conditions in random order: routine footwear (CON), a 5° valgus heel wedge (WED) and an off-the-shelf orthosis modified such that the rearfoot is maintained in 5° valgus (ORT). Because we wanted to know whether foot orthoses were effective through a mechanical effect rather than a neuromuscular adaptation, the study investigated only the immediate mechanical effect of these interventions. Each time

Dynamic measurements

No differences were found between conditions in the spatio-temporal variables including gait velocity, cadence and stride length (Table 2). Kinematics of the tibia relative to the femur (peak external and internal rotation) also did not differ between conditions (P=0.30). No temporal shift in the waveforms of the knee joint kinematics was visually observed between conditions.

Kinetic data from nine subjects collected during level walking are presented in Table 3. Gait data from three subjects

Discussion

It was hypothesized that both a 5° valgus heel wedge and 5° valgus modified orthosis move the center of pressure laterally during walking shortening the adduction moment arm and decreasing the joint moment. Changes in the adduction moment infer changes in the load distribution across the knee joint, which could explain why these shoe inserts reduce pain and increase capacity in OA patients. However, we found no differences in the peak displacement of the center of pressure along the laboratory y

Conclusions

The use of a 5° valgus heel wedge and 5° valgus modified orthosis did not affect the static alignment or knee adduction moment in level walking in a sample of people with mild to moderate medial compartment knee OA. The proposed mechanism that hypothesized a lateral shift in the center of pressure resulted in a reduced adduction moment in this population was not supported. However, the significant reduction in the peak displacement of center of pressure relative to the x-axis of the laboratory

Acknowledgements

Financial contributions to this study have been provided by the Drummond Foundation and the Natural Sciences and Engineering Research Council of Canada. Superfeet® donated the orthoses and wedge material used in this study. The authors would like to thank Dr. J. Rudan for assisting in study design and subject recruitment, and the physical therapists at Providence Continuing Care Center at St. Mary's site for their assistance with subject recruitment.

References (32)

  • O. Schipplein et al.

    Interaction between active and passive knee stabilizers during level walking

    J. Orthop. Res.

    (1991)
  • I. Harrington

    Static and dynamic loading patterns in knee joints with deformity

    J. Bone Joint Surg.

    (1983)
  • R. Bourne et al.

    In vitro strain distribution in the proximal tibia

    Clin. Orthop. Rel. Res.

    (1984)
  • R. Grelsamer

    Unicompartmental osteoarthrosis of the knee

    J. Bone Joint Surg.

    (1995)
  • F. Pollo

    Bracing and heel wedging for unicompartmental osteoarthritis of the knee

    Am. J. Knee Surg.

    (1998)
  • T. Sasaki et al.

    Clinical evaluation of the treatment of osteoarthritic knees using a newly designed wedged insole

    Clin. Orthop. Rel. Res.

    (1987)
  • Cited by (92)

    • Finite element analysis of knee and ankle joint during gait based on motion analysis

      2019, Medical Engineering and Physics
      Citation Excerpt :

      In the present study, contact pressure distributions at the knee and ankle cartilage were obtained with respect to the 1st peak stance phase, mid-stance phase, and 2nd peak stance phase since the contact pressure at the cartilage is known to be a main factor in arthritis. However, in many studies that evaluated the effects of treatments on arthritis with medical aids, kinetic or kinematic analyses could not produce contact pressure distributions at the knee and ankle cartilage during motion [49–51]. Thus, the proposed method is expected to provide a foundation for evaluating medical aid effects.

    View all citing articles on Scopus
    View full text