The effect of internal and external foot rotation on the adduction moment and lateral–medial shear force at the knee during gait

doi:10.1016/j.jsams.2007.03.004

Journal of Science and Medicine in Sport

Volume 11, Issue 5, September 2008, Pages 444-451

https://doi.org/10.1016/j.jsams.2007.03.004 Get rights and content

Summary

It has been hypothesised that those with medial compartment knee osteoarthritis tend to externally rotate their foot during gait in order to unload the diseased compartment. This has been found to decrease the adduction moment at the knee during late stance, although the effects of foot rotation on shear forces at the knee have not yet been determined. Also, the effects of internal foot rotation on the knee during gait are not clear. This study performed a gait analysis on 11 healthy participants (M: 6; mean age 22.9 ± 1.8 years) in three conditions: (1) natural foot rotation position; (2) internal foot rotation and (3) external foot rotation. Three-dimensional gait analysis calculated the knee adduction moment and lateral–medial shear force for all three foot rotation conditions. Internal rotation of the foot increased the knee adduction moment and lateral–medial shear force magnitude during late stance, while external rotation of the foot decreased the magnitude of both these measures. This implies that walking with an externally and internally rotated foot may unload the diseased compartment for those with medial and lateral compartment knee OA, respectively. Also, the relationship of foot rotation angle to the adduction moment and lateral–medial shear force was strengthened when data were corrected for the subject's normal walking condition. Knee OA subject data revealed that they were able to reduce the knee adduction moment more than normal subjects during late stance, indicating that other factors besides the rotation of the foot need to be investigated.

Introduction

Recently, there has been great interest in the mechanical factors that contribute to the development and progression of knee OA. Since OA involves the degeneration of cartilage, it is believed that the interaction between functional, anatomical and biological factors should be considered when attempting to determine OA's rate of progression.¹ However, it is generally accepted that abnormal loading of the articular cartilage over time contributes to cartilage wear and eventually to knee OA. This suggests that the knee's loading environment should be considered when evaluating strategies to delay or prevent the progression of osteoarthritis. Two measures of cartilage loading that have been implicated are the knee's adduction moment2, 3 and lateral–medial shear force created during walking.4, 5

In general terms, the knee's adduction moment is due to the ground reaction force vector acting medially to the knee's axis of rotation in the frontal plane, causing an external moment that would tend to rotate the tibia medially relative to the femur. Mechanically, a large adduction moment increases the load on the knee's medial compartment and is a risk factor for medial knee OA if the resulting compressive force is abnormally high. This is supported by studies that show that the magnitude of the adduction moment determines the load distribution between the medial and lateral compartments of the knee joint² and that its magnitude predicts the progression of OA.³ Additionally, people with medial compartment knee OA have a higher knee adduction moment than normal controls.3, 6

It is possible that, since an abnormally high adduction moment is a risk factor for medial OA, perhaps an abnormally low adduction moment is a risk factor for lateral OA. Historically, few studies have examined lateral knee OA as it was assumed to be a relatively rare condition. However, a more recent study has reported that lateral OA is more common in certain populations than originally thought.⁷ Two recent studies have demonstrated the relationship between lateral OA and a reduced adduction moment. In both a cross-sectional study of preoperative medial (n = 15) and lateral (n = 15) OA,⁸ and in a longitudinal case study that tracked the gait patterns of previously healthy, asymptomatic older adults over a 5–11-year follow-up period,⁴ lateral OA subjects had significantly smaller adduction moments compared to normal controls.

Along with the adduction moment, shear loads at the knee might also need to be considered. Several studies have examined the effects of shear stress on animal and cadaver cartilage in vitro9, 10, 11, 12 and have determined that shear forces are detrimental to cartilage health. The mechanism for the detrimental effect is not clear. Some researchers have implicated biochemical pathways,9, 10, 11 while others have implicated mechanical factors.12, 13 It has also been suggested that the shear forces experienced by the knee during gait may be important in helping to explain cartilage loss and the development of OA.⁴ Also, a study using principal components analysis and descriminant analysis of nine gait curves (three-dimensional forces, moments and angles) and eight discrete measures was successfully able to discriminate between an osteoarthritic and a normal population.⁵ The lateral–medial shear force was the variable explaining most of the variation in the first discriminatory feature and was also a factor in the second most discriminatory feature. In comparison, the adduction moment contributed less than the LM force to the percent variation explained for the first most discriminatory feature, and was not identified as a major contributing factor to the second most discriminatory feature. Therefore, shear forces appear to be an important factor in the progression of knee OA.

Those with symptomatic medial OA often try to unload the diseased medial compartment by walking with an externally rotated foot.¹⁴ This foot rotation decreases the adduction moment during late stance when the whole foot is in contact with the ground15, 16, 17, 18 and is thought to be an effective compensation strategy for those with medial compartment knee OA. Conversely, it may be speculated that walking with an internally rotated foot might be an effective strategy to unload the lateral compartment in lateral knee OA, although this has never been investigated. One study that examined the gait patterns of children aged 11–13 years attempted to test the knee kinetics with an intentional toe-in and toe-out gait and compare that to their normal gait patterns.¹⁹ They reported that the toe-in gait pattern increased the adduction moment, but there were no differences between the toe-out condition and the normal foot position condition; yet this study did not perform separate analyses of early- and late-stance values. Also, Lin et al.¹⁹ did not find a difference between the toe-out condition and normal foot position condition, which contradicts the current literature. This may be due to the fact that they did not perform separate analyses of both early- and late-stance curve parameters.

Although the effect of foot rotation on the knee's adduction moment has been investigated, to our knowledge, the effect of foot rotation on the shear forces has never been previously examined. Therefore, this study will examine the effect of both internal and external foot rotation on the knee adduction moment (KAM) as well as on the lateral–medial force (LMF) created during level walking.

Section snippets

Subjects

The participants were 11 (M: 6) healthy university students with no previous history of lower limb trauma or surgery. The university's Research Ethics Board approved the study and the participants provided informed consent. The average age of participants was 22.9 years (1.8) with an average height of 176.7 cm (11.5) and an average weight of 72.4 kg (14.4).

Gait analysis

Data were collected with a modified version of a three-dimensional gait analysis system that has previously been described and validated.20, 21

Results

Repeated measures ANOVA on the KAM_L and LMF_L variables revealed a main effect for foot rotation and significance on all three individual contrasts; therefore all foot positions were significantly different. Thus, external rotation of the foot significantly decreased the magnitude of the KAM and LMF curves during late stance while internally rotating the foot increased their magnitude (Fig. 1 and Table 1). There was no significant main effect for the KAM_E or LMF_E.

The uncorrected KAM_L and LMF_L

Discussion

The results demonstrate the previously described relationship between foot rotation and the adduction moment during the late-stance phase of gait15, 16, 17, 18 and they also extend the relationship to include the internal rotation of the foot. They demonstrate that, as the foot is rotated externally, the adduction moment decreases and, when the foot is rotated internally, the adduction moment increases during late stance. The adduction moment is a good predictor of the ratio of

Practical implications

•
External rotation of the foot during gait shifts the load off the medial knee compartment, while internal rotation of the foot during gait shifts the load off the lateral knee compartment.
•
Interventions aimed at normalising the adduction moment and medial–lateral shear forces across the knee during gait may help reduce pain and delay the onset and progression of knee OA.
•
Knee OA patients are able to reduce the adduction moment at the knee much more than normal subjects during late stance,

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Cited by (63)

Frontal plane knee moment in clinical gait analysis: A systematic review on the effect of kinematic gait changes
2022, Gait and Posture
Citation Excerpt :
As for the strategy to change the foot progression angle to lower KAMs, both in- and out-toeing can be effectively used as previously described in a different systematic review [18]. Summarizing from studies included in the current review, KAM1 can be reduced with toe-in gait [17,34], whereas KAM2 may be reduced by out-toeing gait [15,17]. Further, a more external foot progression angle (out-toeing) might be adopted with a wider step width gait pattern, to achieve a reduced knee moment [41].
The frontal plane knee moment (KAM1 and KAM2) derived from non-invasive three-dimensional gait analysis is a surrogate measure for knee joint load and of great interest in clinical and research settings. Many aspects can influence this measure either unintentionally or purposely in order to reduce the knee joint load to relieve symptoms and pain. All these aspects must be known when conducting a study or interpreting gait data for clinical decision-making.
This systematic review was registered with PROSPERO (CRD42020187038). Pubmed and Web of Science were searched for peer-reviewed, original research articles in which unshod three-dimensional gait analysis was undertaken and KAM1 and KAM2 were included as an outcome variable. Two reviewers independently screened articles for inclusion, extracted data and performed a methodological quality assessment using Downs and Black checklist.
In total, 42 studies were included. Based on the independent variable investigated, these studies were divided into three groups: 1) gait modifications, 2) individual characteristics and 3) idiopathic orthopedic deformities. Among others, fast walking speeds (1) were found to increase KAM1; There were no sex-related differences (2) and genu valgum (3) reduces KAM1 and KAM2.
While consistent use of terminology and reporting of KAM is required for meta-analysis, this review indicates that gait modifications (speed, trunk lean, step width), individual characteristics (body weight, age) and idiopathic orthopedic deformities (femoral or tibial torsion, genu valgum/varum) influence KAM magnitudes during walking. These factors should be considered by researchers when designing studies (especially of longitudinal design) or by clinicians when interpreting data for surgical and therapeutic decision-making.
Gait modification with subject-specific foot progression angle in people with moderate knee osteoarthritis: Investigation of knee adduction moment and muscle activity
2022, Knee
Subject-specific foot progression angle (SSFPA) as a personalized gait modification is a novel approach to specifically reducing knee adduction.
This study aimed to investigate the effect of gait modification with SSFPA on the knee adduction moment and muscle activity in people with moderate knee osteoarthritis (KOA).
In this clinical trial, nineteen volunteers with moderate KOA were instructed to walk in four different foot progression angle conditions (5° toe-out, 10° toe-out, 5° toe-in, and 10° toe-in) to determine SSFPA that caused the greatest reduction in the greater peak of the knee adduction moment (PKAM). Immediately and after 30 minutes of gait modification with SSFPA, peak root means square (PRMS) and medial and lateral co-contraction index (CCI) were evaluated in the knee muscles.
Walking with 10° toe-in showed the most reduction in the greater PKAM (17.52 ± 15.39%) compared to 5° toe-in (7.1 ± 19.14%), 10° toe-out (1.26 ± 23.13%), and 5° toe-out (7.64 ± 16.71%). As the immediate effect, walking with SSFPA caused a 20.71 ± 12.07% reduction in the greater PKAM than the basic FPA (p < 0.001). After 30 minutes of gait retraining, the greater PKAM decreased by 10.36 ± 26.24%, but this reduction was not significant (p = 0.17). In addition, PRMS of lateral gastrocnemius increased (p = 0.04), and lateral CCI increased 10.72% during late stance (p = 0.04).
Our findings suggest the immediate effect of gait modification with SSFPA on decreasing the knee adduction moment. After gait retraining with SSFPA, the increase of lateral muscle co-contraction may enhance lateral knee muscle co-activity to unload the medial knee compartment.
Clinical Trial Register Number: IRCT20101017004952N8.
Effect of trunk muscles fatigue on plantar pressure distribution in novice runners
2021, Journal of Biomechanics
Citation Excerpt :
This increased loads on the lateral border of the foot following decreased foot progression angle could be transmitted to the proximal areas such as lateral compartment of the knee, that is previously reported by Koblauch et al., showing that the decreases in the foot progression angle increases compressive forces on the lateral compartment of the knee (Koblauch et al. 2013). This is a lateral shift of knee joint loading previously reported by Lynn et al., (Lynn, Kajaks, and Costigan 2008), Shull et al., (Shull et al. 2013) and Khan et al., (Khan, Khan, and Usman 2017), showing that gait with lesser progression angle reduces loading of medial compartment of the knee. In this study trunk muscles fatigue-induced changes in plantar loading were relatively small.
During running, trunk muscles act to sufficiently contribute to the energy generation and transmission of the body parts. Improper function of trunk muscles affects running mechanics adversely and could result in altered lower limb energetics. The aim of this study was to examine the effects of trunk muscles fatigue on plantar pressure distribution in novice runners. 46 novice heel-to-toe runners (26 female and 20 male) ran in 3.3 m/s before and after the trunk muscles fatigue along the plantar pressure measuring device. Then, participants performed trunk muscles fatigue protocol. Trunk muscles fatigue protocol consisted of four consecutive cycles of seven exercises (1) rotating trunk with a medicine ball in sitting position, 2) prone static torso extension with a medicine ball, 3) rotate lower torso with a medicine ball in supine position, 4) incline sit-ups with a weight plate, 5) lateral side binding with a weight plate, 6) rotating lumbar extension with weighted plate, and 7) standing trunk rotation with weighted pulley resistant. After trunk muscles fatigue, increases in loading of lesser toes (p = 0.001, ES = 0.379), fourth (p = 0.001, ES = 0.474) and fifth metatarsals (p = 0.004, ES = 0.173) and medial and lateral heel (p = 0.018,0.001, ES = 0.118,0.427) were observed. Also, foot progression angle (p = 0.001, ES = 392) and relative time of initial contact phase (p = 0.003, ES = 0.182) decreased. The trunk muscles fatigue could alter the plantar pressure distribution pattern. Novice runners should consider strengthening of the trunk region muscles to avoid trunk muscles strength reduction-related changes in running mechanics.
Effects of idiopathic flatfoot deformity on knee adduction moments during walking
2021, Gait and Posture
Citation Excerpt :
On the other hand, KAM2 improved after flatfoot correction while arch height did not significantly increase. In terms of practical research, KAM is an important parameter as it is an indicator of knee joint loading and has been extensively investigated in the field of clinical gait analysis [10–14,20]. Several gait modifications and orthopedic malalignments, such as trunk lean and in-toeing, are known to influence KAM [28].
Flatfoot deformity is commonly characterized by a subtalar valgus, a low medial longitudinal arch, and abduction of the forefoot. Although flatfoot deformity has been associated with lower first (KAM1) and second (KAM2) peak knee adduction moments during walking, the biomechanical connection remains unknown.
We hypothesized that hindfoot eversion, lateral calcaneal shift correlate with KAM1 and forefoot abduction and arch height with KAM2, due to the lateralization of the ground reaction force vector resulting from shifted heel and forefoot in flatfoot deformity.
Gait data from 103 children with flatfoot deformity who underwent three-dimensional gait analysis with the Oxford Foot Model were retrospectively included. Children with knee varus/valgus, in- and out-toeing were excluded. Fifteen healthy children with a rectus foot type were also collected from the database. Lateral calcaneal shift was defined as the distance between the projection of the ankle joint center onto the calcaneal axis and the midpoint of the calcaneal axis formed by the medial and lateral calcaneal markers. A subgroup of children with idiopathic flatfoot deformity that had received corrective surgery was also identified. Statistical analysis included Pearson’s correlations and independent and paired t-tests (α < .05).
When compared to a norm cohort, flatfooted children had significant lower KAM1 and KAM2 (t-test, P < .001). Lateral calcaneal shift correlated with KAM1 and KAM2 (r = 0.42, p < .001 and r = 0.32, P < .001, respectively). Arch height correlated with KAM2 (r = 0.23, p = 0.017). KAM1 and KAM2 normalized after surgery and the change in KAM1 correlated with the change in lateral calcaneal shift for children who underwent corrective surgery.
Lateral calcaneal shift explains the reduction of KAM1 by lateralization of the point of force application in flatfooted children. It is recommended to consider the lateral calcaneal shift when investigating KAM in gait analysis research.
Compensatory mechanisms in children with idiopathic lower extremity internal rotational malalignment during walking and running
2020, Gait and Posture
Noticeable in-toeing gait is present in most children with internal rotational malalignment and often a reason to consult an orthopedic specialist. The risk of tripping may be higher for these patients.
The aim of this study was to determine compensatory mechanisms adopted by children with internal rotational deformities to avoid tripping and falling during walking and running.
Sixty-nine patients between 5–18 years with idiopathic internal rotational malalignment were retrospectively included and subdivided into three groups: 18 patients with internal tibial torsion (ITT), 25 patients with internal femoral torsion (ITF) and 26 patients with both (ITB). Twenty-two typically developing age-matched children (TD) were analyzed for comparison. Three-dimensional gait data were evaluated. ANOVA’s on two factors, group (ITT, ITF, ITB, TD) and movement (walking, running) with post-hoc t-tests were used to identify significant differences between groups.
All groups had significantly greater step width than TD during walking (P ≤ .002) and all torsional groups had significantly greater step width during running (P ≤ .001). Similarly, all torsional groups showed greater peak ankle dorsiflexion in swing during running than TD (P ≤ .006). Only the ITT group showed significantly greater external hip rotation than TD. When compared to TD, the ITF and ITB group had a significantly lower hip abduction moment in stance during running, but not for walking (P ≤ .032).
Compensatory mechanisms in children with internal rotational deformities were mostly dependent on the location of rotational malalignment. All children with internal rotational malalignment had greater ankle dorsiflexion and greater step width during running. Especially in active patients, this greater ankle dorsiflexion during running may result in overuse of the ankle dorsiflexor muscles, while greater step width may have beneficial effects in normalizing knee adduction moments.
Effect of walking with a modified gait on activation patterns of the knee spanning muscles in people with medial knee osteoarthritis
2020, Knee
To evaluate muscle activation patterns and co-contraction around the knee in response to walking with modified gait patterns in patients with medial compartment knee-osteoarthritis (KOA).
40 medial KOA patients walked on an instrumented treadmill. Surface EMG activity from seven knee-spanning muscles (gastrocnemius, hamstrings, quadriceps), kinematics, and ground reaction forces were recorded. Patients received real-time visual feedback on target kinematics to modify their gait pattern towards three different gait modifications: Toe-in, Wider steps, Medial Thrust. The individualized feedback aimed to reduce their first peak knee adduction moment (KAM) by ≥ 10%. Changes in muscle activations and medial/lateral co-contraction index during the loading response phase (10–35% of the gait cycle) were evaluated, for the steps in which ≥ 10% KAM reduction was achieved.
Data from 30 patients were included in the analyses; i.e. all who could successfully reduce their KAM in a sufficient number of steps by ≥ 10%. When walking with ≥ 10% KAM reduction, Medial Thrust gait (KAM − 31%) showed increased flexor activation (24%), co-contraction (17%) and knee flexion moment (35%). Isolated wider-step gait also reduced the KAM (− 26%), but to a smaller extent, but without increasing muscle activation amplitudes and co-contraction. Toe-in gait showed the greatest reduction in the KAM (− 35%), but was accompanied by an increased flexor activation of 42% and hence an increased co-contraction index.
Gait modifications that are most effective in reducing the KAM also yield an increase in co-contraction, thereby compromising at least part of the effects on net knee load.

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Original paperThe effect of internal and external foot rotation on the adduction moment and lateral–medial shear force at the knee during gait

Summary

Introduction

Section snippets

Subjects

Gait analysis

Results

Discussion

Practical implications

Knee

Clin Biomech

J Orthop Res

Semin Arthritis Rheum

J Sci Med Sport

J Orthop Res

Gait Posture

Gait Posture

J Biomech

J Biomed Eng

J Biomech

J Electromyogr Kinesiol

A framework for the in vivo pathomechanics of osteoarthritis at the knee

Ann Biomed Eng

Original paper
The effect of internal and external foot rotation on the adduction moment and lateral–medial shear force at the knee during gait