Toe-in gait reduces the first peak knee adduction moment in patients with medial compartment knee osteoarthritis☆
Introduction
Symptomatic knee osteoarthritis (OA) affects 12% of adults over age 60 years (Dillon et al., 2006) and its prevalence is projected to increase as life expectancy and obesity rates rise (Elders, 2000). The medial compartment of the knee is affected ten times more often than the lateral compartment, likely due to greater medial compartment loading during walking (Ahlback, 1968, Schipplein and Andriacchia, 1991). The external knee adduction moment (KAM) during walking gait is a surrogate measure of medial compartment loading (Zhao et al., 2007, Birmingham et al., 2007). The KAM typically has two peaks: a first peak during early stance and a second peak during late stance. The first, and the larger, peak in the KAM has been linked to the presence (Hurwitz et al., 2002), severity (Sharma et al., 1998), and progression (Miyazaki et al., 2002) of knee OA.
Gait modifications to lower the KAM have been suggested as a conservative treatment for patients with medial compartment knee OA. The foot progression angle is defined by the angle between the foot vector (calcaneous to the second metatarsal) and the line of progression (Rutherford et al., 2008). In normal gait, the foot progression angle is around 5°, indicating toes pointing slightly outward (Rutherford et al., 2008, Guo et al., 2007). Toe-out gait, defined as an increase in foot progression angle from baseline through external foot rotation (Wang et al., 1990, Jenkyn et al., 2008), reduces the second peak of the KAM but not the first peak (Guo et al., 2007, Lynn and Costigan, 2008, Lynn et al., 2008, Fregly et al., 2008). During stair climbing, toe-out gait reduces the second peak KAM but increases the first peak (Guo et al., 2007). Toe-in gait, defined as a decrease in foot progression angle from baseline through internal foot rotation, has been studied comparatively less. Lynn and Costigan (2008) reported that toe-in gait reduced the first peak KAM in healthy adults, while Lin et al. (2001) reported that toe-in gait did not change the first peak KAM and increased the second peak KAM in healthy children.
Gait modifications that are designed to alter the KAM can also change the external knee flexion moment, which may alter joint contact force (Walter et al., 2010). It is possible that gait modifications may decrease the KAM while simultaneously increasing the external knee flexion moment. An increased external knee flexion moment necessitates greater force development by the quadriceps and can eliminate reductions in the medial compartment force brought about by a reduced KAM (Walter et al., 2010). Thus, there is motivation to develop gait modifications for patients with medial-compartment knee OA that lower the first peak KAM without increasing the peak external knee flexion moment.
The mechanism linking changes in foot progression angle to changes in the KAM is not fully understood. It is thought that toe-out gait causes the center of pressure to move laterally, shifting the line of action of the ground reaction force toward the knee joint center (Guo et al., 2007, Jenkyn et al., 2008). This change could reduce the lever arm of the ground reaction force (Hunt et al., 2006) and reduce the magnitude of the KAM; however, experimental data supporting this theory have not been reported. A prior study, in which subjects were instructed to make modifications only to the foot progression angle and separately to make modifications only to the frontal plane tibia angle, found that foot progression and frontal plane tibia angles were moderately correlated (r=0.60, Shull et al., 2010). This suggests that an instructed change in foot progression angle could be accompanied by a frontal plane tibia angle change, which could shift the knee joint center medially for toe-in gait. Thus, it may be too simplistic to assume that changes in the KAM from an altered foot progression angle arise from a change in the center of pressure alone.
We undertook this study to determine the effect of toe-in gait on the first peak knee adduction moment and the peak external knee flexion moment in patients with medial compartment knee osteoarthritis. We hypothesized that: (a) toe-in gait reduces the first peak knee adduction moment, and (b) toe-in gait does not increase the peak external knee flexion moment. We expected that reductions in the knee adduction moment would occur as the knee joint center moved medially and the center of pressure moved laterally, thereby reducing the lever arm of the ground reaction force vector.
Section snippets
Subjects
Twelve subjects (Table 1) with symptomatic, medial-compartment knee OA participated in this study after giving informed consent in accordance with Stanford University's Institutional Review Board. A priori pairwise sample size calculation (power: 95%, alpha: 5%), based on a cohort of healthy subjects from a previous study (Shull et al., 2011), was used to determine that twelve subjects were sufficient to detect a 10% reduction in the KAM. To be included, subjects were required to have
Results
Subjects, on average, reduced their foot progression angle by 5° (p<0.01) during toe-in trials compared to baseline walking trials (Fig. 1, Table 2). Toe-in gait reduced the first peak of the KAM (p<0.01) by an average of 13% (Fig. 2, Table 2). Toe-in gait did not change the ground reaction force vector magnitude (p=0.30) but shortened the lever arm of the ground reaction force vector (p<0.01) by an average of 13% (Fig. 2, Table 2). The tibia angle was not significantly different, though it
Discussion
The purpose of this study was to determine whether toe-in gait reduces the first peak of the KAM without increasing the peak external knee flexion moment in patients with medial compartment knee OA. In support of our first hypothesis, toe-in gait significantly reduced the first peak of the knee adduction moment, which occurred as the knee joint center shifted medially and the center of pressure shifted laterally. The second hypothesis was also supported; toe-in gait did not increase the peak
Conflict of interest statement
None of the authors had any conflict of interest regarding this manuscript.
Acknowledgments
The authors would like to thank Dr. Stuart Goodman for advice and for his assistance in recruiting knee OA patients for this study. This work was supported by the National Science Foundation through the Human-Centered Computing program, grant #1017826.
References (38)
- et al.
Gait retraining to reduce the knee adduction moment through real-time visual feedback of dynamic knee alignment
Journal of Biomechanics
(2010) - et al.
A variable-stiffness shoe lowers the knee adduction moment in subjects with symptoms of medial compartment knee osteoarthritis
Journal of Biomechanics
(2008) - et al.
The influence of foot progression angle on the knee adduction moment during walking and stair climbing in pain free individuals with knee osteoarthritis
Gait and Posture
(2007) - et al.
Feasibility of a gait retraining strategy for reducing knee joint loading: Increased trunk lean guided by real-time biofeedback
Journal of Biomechanics
(2011) - et al.
The knee adduction moment during gait in subjects with knee osteoarthritis is more closely correlated with static alignment than radiographic disease severity, toe out angle and pain
Journal of Orthopaedic Research
(2002) - et al.
Toe-out gait in patients with knee osteoarthritis partially transforms external knee adduction moment into flexion moment during early stance phase of gait: A tri-planar kinetic mechanism
Journal of Biomechanics
(2008) - et al.
The effect of changing the foot progression angle on the knee adduction moment in normal teenagers
Gait and Posture
(2001) - et al.
Effect of foot rotation on knee kinetics and hamstring activation in older adults with and without signs of knee osteoarthritis
Clinical Biomechanics
(2008) - et al.
The effect of internal and external foot reotation on the adduction moment and lateral-medial shear force at the knee during gait
Journal of Science Medicine Sport
(2008) - et al.
Implications of increased medio-lateral trunk sway for ambulatory mechanics
Journal of Biomechanics
(2008)
Foot progression angle and the knee adduction moment: a cross-sectional investigation in knee osteoarthritis
Osteoarthritis and Cartilage
Training multi-parameter gaits to reduce the knee adduction moment with data-driven models and haptic feedback
Journal of Biomechanics
ISB recommendation on definitions of joint coordinate system of various joints for the reporting of human joint motion - part I: ankle, hip, and spine
Journal of Biomechanics
Osteoarthrosis of the knee. A radiographic investigation
Acta Radiologica: Diagnosis Suppl.
Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee
Journal of Rheumatology
Test-retest reliability of the peak knee adduction moment during walking in patients with medial compartment knee osteoarthritis
Arthritis and Rheumatism
The effect of a subject-specific amount of lateral wedge on knee mechanics in patients with medial knee osteoarthritis
Journal of Orthopaedic Research
Prevalence of knee osteoarthritis in the United States: arthritis data from the Third National Health and Nutrition Examination Survey 1991–94
Journal of Rheumatology
Cited by (163)
Toe-out gait inhibits medial meniscus extrusion associated with the second peak of knee adduction moment during gait in patients with knee osteoarthritis
2023, Asia-Pacific Journal of Sports Medicine, Arthroscopy, Rehabilitation and TechnologyVerification of biomechanical factors of gait related to medial knee loading in patients 6 Months after total knee arthroplasty
2023, Journal of Clinical Orthopaedics and Trauma
- ☆
All authors have made substantial contributions to the following: (1) the conception and design of the study, or acquisition of data, or analysis and interpretation of data; (2) drafting the article or revising it critically for important intellectual content; (3) final approval of the version to be submitted. Each of the authors has read and concurs with the content in the manuscript. The manuscript and the material within have not been and will not be submitted for publication elsewhere.