Static and dynamic biomechanics of foot orthoses in people with medial compartment knee osteoarthritis
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)
- et al.
Osteoarthritis in ankle and knee joints
Semin. Arthritis Rheum.
(1997) - et al.
Radiographic assessment of bony contributions to knee deformity
Orthop. Clin. North Am.
(1994) The mechanics of the knee joint in relation to normal walking
J. Biomech.
(1970)- et al.
Laterally elevated wedged insoles in the treatment of medial knee osteoarthritis: A prospective randomized controlled study
Osteoarthr. Cartilage
(2001) - et al.
Relationships between alignment, kinematic and kinetic measures of the knee of normal elderly subjects in level walking
Clin. Biomech.
(1994) - et al.
A procedure to validate three-dimensional motion assessment systems
J. Biomech.
(1993) Dynamics of knee malalignment
Orthop. Clin. North Am.
(1994)- et al.
An update on the epidemiology of knee and hip osteoarthritis with a view to prevention
Arthritis Rheum.
(1998) - et al.
The effects of specific medical conditions on the functional limitations of elders in the Framingham study
Am. J. Public Health
(1994) - et al.
A method for quantitative analysis of medial and lateral compression forces at the knee during standing
Clin. Orthop. Rel. Res.
(1972)
Interaction between active and passive knee stabilizers during level walking
J. Orthop. Res.
Static and dynamic loading patterns in knee joints with deformity
J. Bone Joint Surg.
In vitro strain distribution in the proximal tibia
Clin. Orthop. Rel. Res.
Unicompartmental osteoarthrosis of the knee
J. Bone Joint Surg.
Bracing and heel wedging for unicompartmental osteoarthritis of the knee
Am. J. Knee Surg.
Clinical evaluation of the treatment of osteoarthritic knees using a newly designed wedged insole
Clin. Orthop. Rel. Res.
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