Developing an estimate of daily cumulative loading for the knee: examining test-retest reliability

Cumulative loading increases and loading asymmetries persist during walking for people with a transfemoral bone-anchored limb

BACKGROUND

A bone-anchored limb (BAL) is an alternative to a traditional socket-type prosthesis for people with transfemoral amputation. Early laboratory-based evidence suggests improvement in joint and limb loading mechanics during walking with a BAL compared to socket prosthesis use. However, changes in cumulative joint and limb loading measures, which may be predictive of degenerative joint disease progression, remain unknown.

RESEARCH QUESTION

Do cumulative total limb and hip joint loading during walking change using a BAL for people with unilateral transfemoral amputation, compared to prior socket prosthesis use?

METHODS

A case-series cohort of eight participants with prior unilateral transfemoral amputation who underwent BAL hardware implantation surgery were retrospectively analyzed (4 M/4 F; BMI: 27.7 ± 3.1 kg/m2; age: 50.4 ± 10.2 years). Daily step count and whole-body motion capture data were collected before (using socket prosthesis) and one-year after BAL hardware implantation. Cumulative total limb and hip joint loading and between-limb loading symmetry metrics were calculated during overground walking at both time points and compared using Cohen's d effect sizes.

RESULTS

One year after BAL hardware implantation, participants demonstrated bilateral increases in cumulative total limb loading (amputated: d = -0.65; intact: d = -0.72) and frontal-plane hip moment (amputated: d = -1.29; intact: d = -1.68). Total limb loading and hip joint loading in all planes remained asymmetric over time, with relative overloading of the intact limb in all variables of interest at the one-year point.

SIGNIFICANCE

Despite increases in cumulative total limb and hip joint loading, between-limb loading asymmetries persist. Habitual loading asymmetry has been implicated in contributing to negative long-term joint health and onset or progression of degenerative joint diseases. Improved understanding of methods to address habitual loading asymmetries is needed to optimize rehabilitation and long-term joint health as people with transfemoral amputation increase physical activity when using a BAL.

Cumulative knee adduction moment during jogging causes temporary medial meniscus extrusion in healthy volunteers

PURPOSE

The cumulative knee adduction moment (KAM) is a key parameter evaluated for the prevention of overload knee injuries on the medial compartment. Medial meniscus extrusion (MME), typical in hoop dysfunctions, is a measure for the cumulative mechanical stress in individual knees; however, its correlation with cumulative KAM is unknown. The aim of this study was to investigate the effect of temporary overload stress on MME and its correlation with cumulative KAM.

METHODS

Thirteen healthy asymptomatic volunteers (13 knees) were recruited for a cohort study (mean age, 23.1 ± 3.3 years; males: n = 8). The cumulative KAM was calculated using a three-dimensional motion analysis system, in addition to the number of steps taken while jogging uphill or downhill. MME was evaluated using ultrasound performed in the standing position. The evaluations were performed four times: at baseline (T0), before and after (T1 and T2, respectively) jogging uphill or downhill, and 1 day after (T3) jogging. Additionally, the Δ-value was calculated using the change of meniscus after efforts as the difference in MME between T1 and T2.

RESULTS

The MME in T2 was significantly greater than those in T0 and T1. Conversely, the MME in T3 was significantly lesser than that in T2. No significant difference was found between those in T0 and T1, and T3. ΔMME exhibited a significant positive correlation with the cumulative KAM (r = 0.68, p = 0.01), but not for peak KAM.

CONCLUSION

The temporary reaction of MME observed in ultrasound correlates with the cumulative stress of KAM.

Reliability and validity of knee angles and moments in patients with osteoarthritis using a treadmill-based gait analysis system

BACKGROUND

Although commonly used to study knee osteoarthritis (OA), relatively little is known about the reliability and validity of three-dimensional (3D) gait biomechanics derived from treadmill-based systems.

RESEARCH QUESTION

Using a treadmill-based gait analysis system, our objectives were to: 1) estimate the test-retest reliability of frontal and sagittal plane knee angles and moments in knee OA patients; 2) examine concurrent validity by estimating the associations between treadmill-based and overground (gold standard) measures; and 3) examine known-groups validity by comparing measures between knee OA patients and matched healthy controls.

METHODS

34 patients and 16 controls completed 3D gait analyses using treadmill-based and overground systems. Treadmill walking speed was matched to self-selected overground speed. Marker set, knee angle and moment calculations were consistent for both systems. Patients completed a second test session using the treadmill-based system <24 h later but within 1 week of the first test session. Variables calculated from knee angle and moment gait waveforms during stance were evaluated using Bland and Altman plots, Intraclass Correlation Coefficients (ICC), Pearson correlations (r) and t-tests.

RESULTS

Visual inspection of the Bland and Altman plots did not reveal any systematic differences between test and retest sessions; however, limits of agreement (LoA) were larger for the sagittal plane than the frontal plane. Mean differences between sessions for knee angles were <0.25 degrees and <0.18 %BW*ht for knee moments. ICCs ranged from 0.57-to-0.93 for test-retest reliability. Pearson correlations between treadmill and overground systems ranged from 0.56-to-0.97. Although highly associated, there were substantial differences in the moments, emphasizing they cannot be used interchangeably. Patients had greater first peak knee adduction moments (KAM) than controls [mean difference (95 %CI): 0.55 (-1.07, -0.04), p = 0.03].

SIGNIFICANCE

Results suggest frontal and sagittal plane knee angles and moments in patients with knee OA evaluated using a treadmill-based system are reliable and valid.

Using Cumulative Load to Explain How Body Mass Index and Daily Walking Relate to Worsening Knee Cartilage Damage Over Two Years: The MOST Study

OBJECTIVE

Knee cartilage damage is often linked to mechanical overloading. However, cartilage requires mechanical load to remain healthy, suggesting that underloading may be detrimental. This study was undertaken to examine knee overloading and underloading by defining cumulative load as the joint effects of body mass index (BMI) and daily walking, and examine the relationship between cumulative load and worsening cartilage damage over 2 years.

METHODS

We used data from the Multicenter Osteoarthritis Study. Steps/day, measured by accelerometry, and BMI were calculated at the 60-month visit. Cartilage damage on magnetic resonance imaging was semiquantitatively scored using the Whole-Organ Magnetic Resonance Imaging Score (WORMS) at the 60-month and 84-month visits; worsening damage was defined as increased WORMS between visits. Risk ratios (RRs) and 95% confidence intervals (95% CIs) were calculated using binomial regression, with adjustment for potential confounders.

RESULTS

Our study included 964 participants, 62% of whom were female, with a mean ± SD age of 66.9 ± 7.5 years. Participants had a mean ± SD BMI of 29.7 ± 4.8 kg/m² and walked a mean ± SD of 7,153 ± 2,591 steps/day. Participants who walked a moderate number of steps/day (6,000-7,900) or a high number of steps/day (>7,900) and had a high BMI (>31 kg/m² ) had a greater risk of worsening medial tibiofemoral (TF) damage (RR 2.83 [95% CI 1.46-5.48] and RR 2.61 [95% CI 1.50-4.54], respectively) compared with those who walked similar steps/day and had a low BMI (18-27 kg/m² ). Participants with a low number of steps/day (<6,000) and a low BMI had a greater risk of worsening medial TF and lateral patellofemoral (PF) damage (RR 2.03 [95% CI 1.06-3.92] and RR 2.28 [95% CI 1.06-4.85], respectively) compared with those who walked a high number of steps/day and had a low BMI. Effect estimates for other compartments of the knee did not reach statistical significance.

CONCLUSION

This study provides preliminary evidence that both overloading and underloading may be detrimental to medial TF cartilage, and underloading may be detrimental to lateral PF cartilage.

A Machine Learning Approach to Estimate Hip and Knee Joint Loading Using a Mobile Phone-Embedded IMU

Hip osteoarthritis patients exhibit changes in kinematics and kinetics that affect joint loading. Monitoring this load can provide valuable information to clinicians. For example, a patient's joint loading measured across different activities can be used to determine the amount of exercise that the patient needs to complete each day. Unfortunately, current methods for measuring joint loading require a lab environment which most clinicians do not have access to. This study explores employing machine learning to construct a model that can estimate joint loading based on sensor data obtained solely from a mobile phone. In order to learn such a model, we collected a dataset from 10 patients with hip osteoarthritis who performed multiple repetitions of nine different exercises. During each repetition, we simultaneously recorded 3D motion capture data, ground reaction force data, and the inertial measurement unit data from a mobile phone attached to the patient's hip. The 3D motion and ground reaction force data were used to compute the ground truth joint loading using musculoskeletal modeling. Our goal is to estimate the ground truth loading value using only the data captured by the sensors of the mobile phone. We propose a machine learning pipeline for learning such a model based on the recordings of a phone's accelerometer and gyroscope. When evaluated for an unseen patient, the proposed pipeline achieves a mean absolute error of 29% for the left hip and 36% for the right hip. While our approach is a step in the direction of using a minimal number of sensors to estimate joint loading outside the lab, developing a tool that is accurate enough to be applicable in a clinical context still remains an open challenge. It may be necessary to use sensors at more than one location in order to obtain better estimates.

Relative and absolute test-retest reliabilities of biomechanical risk factors for knee osteoarthritis progression: benchmarks for meaningful change

OBJECTIVE

Biomechanical factors are important treatment targets in knee osteoarthritis. The knee adduction (KAM) and flexion (KFM) moments, quadriceps strength and power, load frequency, and body mass index (BMI) all have the potential to affect knee articular cartilage integrity by modulating forces across the joint. To identify clinically meaningful change, however, these measurements must be reliable and sensitive to change. This study estimated relative and absolute test-retest reliabilities over long periods of biomechanical risk factors for knee osteoarthritis progression.

METHOD

Data from a longitudinal, observational study were analyzed for knee osteoarthritis patients with data at baseline, 6-month and 24-month follow-ups. Gait kinematics and kinetics, quadriceps strength and power, daily load frequency and BMI were collected. Relative and absolute test-retest reliabilities of these measures were estimated using intraclass correlation coefficients (ICCs) and standard errors of measurement (SEMs), respectively. Minimal detectable change at the 95% confidence level (MDC95) was also calculated.

RESULTS

Data from 46 participants [36 women; age 61.0 (6.6) years] were included. Good-to-excellent relative reliabilities (ICC ≥ 0.80) indicated that KAM peak and impulse, quadriceps strength and power, and BMI had a strong ability to discriminate amongst participants. Absolute reliabilities were high for quadriceps strength and BMI, which demonstrated reasonable within-participant variability (SEMs ≤ 11% of the mean). The MDC95 values supported use of clinical interventions effective in reducing BMI and KAM, and increasing quadriceps strength.

CONCLUSION

These data are useful in interpreting findings from interventional or longitudinal investigations by determining whether observed changes are beyond measurement error and interpretable as true change.

Baseline knee adduction moment interacts with body mass index to predict loss of medial tibial cartilage volume over 2.5 years in knee Osteoarthritis

This study aimed to determine the extent to which changes over 2.5 years in medial knee cartilage thickness and volume were predicted by: (1) Peak values of the knee adduction (KAM) and flexion moments; and (2) KAM impulse and loading frequency, representing cumulative load, after controlling for age, sex and body mass index (BMI). Adults with clinical knee osteoarthritis participated. At baseline and approximately 2.5 years follow-up, cartilage thickness and volume of the medial tibia and femur were segmented from magnetic resonance imaging scans. Gait kinematics and kinetics, and daily knee loading frequency were also collected at baseline. Multiple linear regressions predicted changes in cartilage morphology from baseline gait mechanics. Data were collected from 52 participants (41 women) [age 61.0 (6.9) y; BMI 28.5 (5.7) kg/m² ] over 2.56 (0.51) years. There were significant KAM peak-by-BMI (p = 0.023) and KAM impulse-by-BMI (p = 0.034) interactions, which revealed that larger joint loads in those with higher BMIs were associated with greater loss of medial tibial cartilage volume. In conclusion, with adjustments for age, sex, and cartilage measurement at baseline, large magnitude KAM peak and KAM impulse each interacted with BMI to predict loss of cartilage volume of the medial tibia over 2.5 years among individuals with knee osteoarthritis. These data suggest that, in clinical knee osteoarthritis, exposure to large KAMs may be detrimental to cartilage in those with larger BMIs. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2476-2483, 2017.

Associations of radiographic degeneration and pain with daily cumulative hip loading in patients with secondary hip osteoarthritis

The purpose of this study was to investigate the associations of radiographic and clinical variables of hip osteoarthritis (OA) with alterations in gait and joint loading in patients with secondary hip OA. Fifty females with secondary hip OA were participated. The minimum joint space width (mJSW) of the hip as a degenerative sign and Sharp and center edge (CE) angles as morphological variables were measured radiographically. Hip joint pain was assessed using a visual analog scale. As gait variables, walking speed, range of hip motion, hip moment peak, and hip moment impulse were calculated. Daily cumulative hip loading was calculated as the hip moment impulse multiplied by the mean number of steps per day. After bivariate correlation analyses between dependent (mJSW and pain) and independent variables (age, body mass index, sharp/CE angles, steps per day, and gait variables), separate forward-backward stepwise multiple regression analyses were performed for each dependent variable. Daily cumulative hip loading in the sagittal plane (β = 0.30, p = 0.021) and age (β = -0.36, p = 0.007) were significantly associated with the mJSW. Walking speed (β = -0.36, p = 0.008) and age (β = 0.29, p = 0.031) were significantly associated with hip joint pain. Decrease in daily cumulative hip loading in the sagittal plane was associated with mJSW independently of age. Although the causal relationship was not clear, patients with hip OA reduced total exposure to hip joint loading adaptively rather than lowering the hip moment peak concerning worsening of hip degeneration. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1977-1983, 2016.

Relationship between knee adduction moment patterns extracted using principal component analysis and discrete measures with different amplitude normalizations: Implications for knee osteoarthritis progression studies

BACKGROUND

Knee adduction moment discrete features (peaks and impulses) are commonly reported in knee osteoarthritis gait studies, but they do not necessarily capture loading patterns. Principal component analysis extracts dynamic patterns, but can be difficult to interpret. This methodological study determined relationships between external knee adduction moment discrete measures and principal component analysis features, and examined whether amplitude-normalization methods influenced differences in those with knee osteoarthritis who progressed to surgery versus those that did not.

METHODS

54 knee osteoarthritis patients had three-dimensional biomechanical measures assessed during walking. Knee adduction moments were calculated and non-normalized and amplitude-normalized waveforms using two common methods were calculated. Patterns were extracted using principal component analysis. Knee adduction moment peak and impulse were calculated. Correlation coefficients were determined between two knee adduction moment patterns extracted and peak and impulse. T-tests evaluated between-group differences.

FINDINGS

An overall magnitude pattern was correlated with peak (r=0.88-0.90, p<0.05) and impulse (r=0.93, p<0.05). A pattern capturing a difference between early and mid/late -stance knee adduction moment was significantly correlated with peak (r=0.27-0.40, p<0.05), but explained minimal variance. Between-group peak differences were only affected by amplitude-normalization method.

INTERPRETATION

Findings suggest that the overall magnitude knee adduction moment principal pattern does not provide unique information from peak and impulse measures. However, low correlations and minimal variance explained between the pattern capturing ability to unload the joint during mid-stance and the two discrete measures, suggests that this pattern captured a unique waveform feature.

Sound limb loading in individuals with unilateral transfemoral amputation across a range of walking velocities

BACKGROUND

Individuals with unilateral transfemoral amputation demonstrate significantly increased rates of osteoarthritis in their sound knee. This increased risk is likely the result of altered knee mechanical loading and gait compensations resulting from limited function in the prosthetic limb. Altered knee loading as calculated using loading rates and peak external knee adduction moments and impulses have been associated with both the development and progression of knee osteoarthritis in other populations. The purpose of this study was to determine if young individuals with transfemoral amputation demonstrate biomechanical indicators of increased knee osteoarthritis risk.

METHODS

Fourteen young male Service Members with unilateral transfemoral amputation and 14 able-bodied service members underwent biomechanical gait analysis at three standardized walking velocities. A two-way ANOVA (group × speed) with unpaired comparisons with Bonferroni-Holm post-hoc corrections assessed statistical significance and effect sizes (d) were calculated.

FINDINGS

Normalized peak external knee adduction moments and impulses were 25.7% (P < 0.014, d > 0.994) and 27.1% (P < 0.012, d > 1.019) lower, respectively, in individuals with trans-femoral amputation than controls when averaged across speeds, and effect sizes were large. External knee flexor moments were not, however, different between groups and effect sizes were generally small (P > 0.380, d < 0.338). Maximal loading rates were significantly greater in individuals with amputation and effect sizes were large (P < 0.001, d > 1.644).

INTERPRETATION

Individuals with transfemoral amputation did not demonstrate biomechanical risk factors for high medial compartment knee joint loads, but the increased loading rates could place the sound knee at greater risk for cartilage or other tissue damage, even if not localized to the medial compartment.

Knee power is an important parameter in understanding medial knee joint load in knee osteoarthritis

Objective

To determine the extent to which knee extensor strength and power explain variance in knee adduction moment (KAM) peak and impulse in clinical knee osteoarthritis (OA).

Methods

Fifty-three adults (mean ± SD age 61.6 ± 6.3 years, 11 men) with clinical knee OA participated. The KAM waveform was calculated from motion and force data and ensemble averaged from 5 walking trials. The KAM peak was normalized to body mass (Nm/kg). The mean KAM impulse reflected the mean total medial knee load during stride (Nm × seconds). For strength, the maximum knee extensor moment attained from maximal voluntary isometric contractions (MVIC) was normalized to body mass (Nm/kg). For power, the maximum knee extensor power during isotonic contractions, with the resistance set at 25% of MVIC, was normalized to body mass (W/kg). Covariates included age, sex, knee pain on the Knee Injury and Osteoarthritis Outcome Score, gait speed, and body mass index (BMI). Relationships of the KAM peak and impulse with strength and power were examined using sequential stepwise forward linear regressions.

Results

Covariates did not explain variance in the KAM peak. While extensor strength did not, peak knee extensor power explained 8% of the variance in the KAM peak (P = 0.02). Sex and BMI explained 24% of the variance in the KAM impulse (P < 0.05). Sex, BMI, and knee extensor power explained 31% of the variance in the KAM impulse (P = 0.02), with power contributing 7% (P < 0.05).

Conclusion

Knee extensor power was more important than isometric knee strength in understanding medial knee loads during gait.

The relationship between knee joint loading rate during walking and degenerative changes on magnetic resonance imaging

BACKGROUND

While animal study and cadaveric study have demonstrated an association between knee joint loading rate and joint degeneration, the relationship between knee joint loading rate during walking and osteoarthritis has not yet been sufficiently studied in humans.

METHODS

Twenty-eight participants (14 transfemoral amputees and 14 age and body mass matched controls) underwent knee MRI with subsequent assessment using the semiquantitative Whole-Organ Magnetic Resonance Image Score. Each subject also underwent gait analysis in order to determine knee adduction moment loading rate, peak, and impulse and an exploratory measure, knee adduction moment rate∗magnitude.

FINDINGS

Significant correlations were found between medial tibiofemoral joint degeneration and knee adduction moment peak (slope=0.42 [SE 0.20]; P=.037), loading rate (slope=12.3 [SE 3.2]; P=.0004), and rate∗magnitude (slope=437 [SE 100]; P<.0001). These relationships continued to be significant after adjusting for body mass or subject type. The relationship between medial knee semiquantitative MRI score and knee adduction moment loading rate and rate∗magnitude continued to be significant even after adjusting for peak moment (P<.0001), however, the relationship between medial knee semiquantitative MRI score and peak moment was no longer significant after adjusting for either loading rate or rate∗magnitude (P>.2 in both cases).

INTERPRETATION

This study suggests an independent relationship between knee adduction moment loading rate and medial tibiofemoral joint degeneration. Our results support the hypothesis that rate of loading, represented by the knee adduction moment loading rate, is strongly associated with medial tibiofemoral joint degeneration independent of knee adduction moment peak and impulse.

Quantity and quality of physical activity are influenced by outdoor temperature in people with knee osteoarthritis

PURPOSE

Environmental factors are known to influence physical activity (PA) levels of healthy people, but little work has explored these factors in people with osteoarthritis (OA). The purpose of this study was to explore the influence of outdoor temperature on PA in people with knee OA.

METHODS

A total of 38 people with knee OA (10 women; mean age 54 y) wore an accelerometer around their waist for 7 consecutive days. Dependent variables from the accelerometers were three PA measures: (1) activity counts/day and time spent at or above moderate levels of PA with (2) a cut-point of 1,041 activity counts/minute (MVPA1041) and (3) a cut-point of 1,952 activity counts/minute (MVPA1952). Independent variables were age, sex, body mass index (BMI), and maximum daily outdoor temperature. Three linear regression analyses were conducted using the three PA dependent variables and independent variables.

RESULTS

After controlling for age, sex, and BMI, maximum daily outdoor temperature explained 9% of the variance in activity counts/day (p=0.042), 10% of variance in MVPA1041 (p=0.032), and 14% of variance in MVPA1952 (p=0.016). Participants who engaged in more PA were younger and were exposed to warmer temperatures.

CONCLUSIONS

Outdoor temperature and age influence the PA levels of people with knee OA. These factors should be considered when designing PA programmes.

Reliability of principal components and discrete parameters of knee angle and moment gait waveforms in individuals with moderate knee osteoarthritis

Gait measures are used to evaluate change in patients with knee osteoarthritis (OA), but reliability has not been fully established in this population. This study examined test-retest reliability of knee angle and moment gait waveform characteristics captured using discrete parameters and principal component analysis (PCA) in individuals with moderate knee OA. Participants (n=20) underwent three-dimensional gait analysis on two occasions. Motion and force data were captured using two camera banks, infrared light emitting diodes and force plate during self-selected walking. Knee angle and moment waveforms were calculated and analyzed using discrete parameters and by identifying waveform characteristics using PCA. Intraclass correlation coefficients (ICC2,k) examined test-retest reliability of discrete parameters and PCA derived scores (PC-scores). ICC2,k values ranged from 0.57 to 0.93 for discrete parameters, 0.52-0.86 for knee angle PC-scores and 0.30-0.94 for the knee moment PC-scores. However, 10 of 13 discrete parameters, six of nine knee angle PC-scores and seven of nine knee moment PC-scores had ICC2,k values greater than or equal to 0.70. Discrete parameters and PC-scores from flexion angles and adduction moments had the highest ICC2,k values while adduction angles, rotation angles, and rotation moments had the lowest. Most knee angle and moment waveform characteristics demonstrated ICC2,k values that could be interpreted as acceptable. Caution should be used when examining adduction and rotation angle magnitudes and early/mid-stance rotation moment magnitudes due to lower ICC2,k values.

Cumulative knee adductor load distinguishes between healthy and osteoarthritic knees--a proof of principle study

Cumulative knee adductor load reflects repetitive exposures to medial knee loading that are encountered during daily activity. The purpose of this proof of principle study was to investigate whether cumulative knee adductor load distinguished between adults with and without knee osteoarthritis (OA). Thirty-one adults with radiographic knee OA (53.2±6.1 years old) and 30 healthy adults (33.5±8.0 years old) participated. A non-normalized knee adduction moment waveform was calculated from gait data collected using a motion analysis system with synchronized force plate. The peak and impulse from knee adduction moment was calculated. Cumulative knee adductor load was the product of the knee adduction moment impulse during stance and the mean number of steps taken per day, measured with a uni-dimensional accelerometer. One thousand bootstrap t-tests determined whether cumulative knee adductor load was at least as good as the peak knee adduction moment in discriminating between the healthy and OA groups. Cumulative knee adductor load was nearly two times larger in the knee OA compared to the healthy group (p=0.001). Cumulative knee adductor load was better than the peak knee adduction moment at discriminating between groups (p=0.04). This work provides evidence of validity for cumulative knee adductor load. In the calculation of cumulative loads, non-normalization of the adduction moment impulse to magnitude or time emphasized the importance of the total loads borne through the medial knee compartment during each step.

The effect of walking poles on the knee adduction moment in patients with varus gonarthrosis

OBJECTIVES

(1) Test the hypothesis that walking poles decrease the external knee adduction moment during gait in patients with varus gonarthrosis, and (2) explore potential mechanisms.

DESIGN

Thirty-four patients with medial compartment knee osteoarthritis (OA) and varus alignment underwent three dimensional (3D) gait analysis with and without using walking poles. Conditions were randomized and walking speed was maintained ±5% of the self-selected speed of the initial condition. The pole held in the hand of the unaffected side was instrumented with a compression load cell.

RESULTS

Student's t tests for paired samples indicated small but statistically significant increases (P < 0.001) in knee adduction moment (calculated from inverse dynamics) for its first peak, second peak and angular impulse when using the poles; mean increases (95% confidence interval - CI) were 0.17%BW*Ht (0.08, 0.27), 0.17%BW*Ht (0.04, 0.30) and 0.15%BW*Ht*s (0.09, 0.22), respectively. There was a decrease (P = 0.015) in vertical ground reaction force (-0.02 BW (-0.04, -0.01)), yet increase (P < 0.001) in its frontal plane lever arm about the knee (0.30 cm (0.15, 0.44)), at the time of the first peak knee adduction moment. Pole force in the vertical direction was inversely related (r = -0.34, P = 0.05) to the increase in first peak adduction moment.

CONCLUSION

Although results are variable among patients, and may be related to individual technique, these overall findings suggest that walking poles do not decrease knee adduction moments, and therefore likely do not decrease medial compartment loads, in patients with varus gonarthrosis. Decreases in knee joint loading should not be used as rationale for walking pole use in these patients.

Combined effects of a valgus knee brace and lateral wedge foot orthotic on the external knee adduction moment in patients with varus gonarthrosis

OBJECTIVE

To test the hypothesis that a custom-fit valgus knee brace and custom-made lateral wedge foot orthotic will have greatest effects on decreasing the external knee adduction moment during gait when used concurrently.

DESIGN

Proof-of-concept, single test session, crossover trial.

SETTING

Biomechanics laboratory within a tertiary care center.

PARTICIPANTS

Patients (n=16) with varus alignment and knee osteoarthritis (OA) primarily affecting the medial compartment of the tibiofemoral joint (varus gonarthrosis).

INTERVENTIONS

Custom-fit valgus knee brace and custom-made full-length lateral wedge foot orthotic. Amounts of valgus angulation and wedge height were tailored to each patient to ensure comfort.

MAIN OUTCOME MEASURES

The external knee adduction moment (% body weight [BW]*height [Ht]), frontal plane lever arm (cm), and ground reaction force (N/kg), determined from 3-dimensional gait analysis completed under 4 randomized conditions: (1) control (no knee brace, no foot orthotic), (2) knee brace, (3) foot orthotic, and (4) knee brace and foot orthotic.

RESULTS

The reduction in knee adduction moment was greatest when concurrently using the knee brace and foot orthotic (effect sizes ranged from 0.3 to 0.4). The mean decrease in first peak knee adduction moment compared with control was .36% BW*Ht (95% confidence interval [CI], -.66 to -.07). This was accompanied by a mean decrease in frontal plane lever arm of .59cm (95% CI, -.94 to -.25).

CONCLUSIONS

These findings suggest that using a custom-fit knee brace and custom-made foot orthotic concurrently can produce a greater overall reduction in the knee adduction moment, through combined effects in decreasing the frontal plane lever arm.

Effect of footwear on the external knee adduction moment - A systematic review

CONTEXT

Footwear modifications have been investigated as conservative interventions to decrease peak external knee adduction moment (EKAM) and pain associated with knee osteoarthritis (OA).

OBJECTIVE

To evaluate the literature on the effect of different footwear and orthotics on the peak EKAM during walking and/or running.

METHODS

A systematic search of databases resulted in 348 articles of which 33 studies were included.

RESULTS

Seventeen studies included healthy individuals and 19 studies included subjects with medial knee OA. Quality assessment (modified Downs and Black quality index) showed an (average±SD) of 73.1±10.1%. The most commonly used orthotic was the lateral wedge, with three studies on the medial wedge. Lateral wedging was associated with decreased peak EKAM in healthy participants and participants with medial knee OA while there is evidence for increased peak EKAM with the use of medial wedges. Modern footwear (subjects' own shoe, "stability" and "mobility" shoes, clogs) were likely to increase the EKAM compared to barefoot walking in individuals with medial knee OA. Walking in innovative shoes ("variable stiffness") decreased the EKAM compared to control shoes. Similarly, shoes with higher heels, sneakers and dress shoes increased EKAM in healthy individuals compared to barefoot walking.

CONCLUSIONS

Further development may be needed toward optimal footwear for patients with medial knee OA with the aim of obtaining similar knee moments to barefoot walking.

Comparative diagnostic accuracy of knee adduction moments in knee osteoarthritis: a case for not normalizing to body size

Previous authors have questioned the practice of normalizing the external knee adduction moment during gait to body size when investigating dynamic joint loading in knee osteoarthritis (OA). The purpose of this study was to compare the abilities of non-normalized and normalized external knee adduction moments during gait in discriminating between patients with least and greatest severity of radiographic medial compartment knee OA. Subjects with mild (n=118) and severe (n=115) medial compartment knee OA underwent three-dimensional gait analysis. The peak external knee adduction moment was calculated and kept in its original units (Nm), normalized to body mass (Nm/kg) and normalized to body weight and height (%BW × Ht). Receiver Operating Characteristic (ROC) curve analysis indicated that non-normalized values better discriminated between patients with mild and severe knee OA. The area under the ROC curve for non-normalized peak knee adduction moments (0.63) was significantly (p<0.05) greater than when normalized to body mass (0.58), or to body weight times height (0.57). Post-hoc analysis of covariance indicated the mean difference in peak knee adduction moment between OA severity groups (7.23 Nm, p=0.003) was reduced by approximately 50% (3.60 Nm, p=0.09) when adjusted for mass. These findings are consistent with the suggestion that non-normalized values are more sensitive to radiographic disease progression. We suggest including knee adduction moment values that are not normalized to body size when investigating knee OA.

Gait after unilateral total knee arthroplasty: frontal plane analysis

After unilateral total knee arthroplasty (TKA), osteoarthritis (OA) in the non-operated knee often progresses. The altered gait mechanics exhibited by patients after TKA increase the loading on the non-operated knee and predispose it to disease progression. Therefore, our objective was to examine the potentially detrimental changes in frontal plane kinetics and kinematics during walking in patients who underwent unilateral TKA. Thirty-one subjects 6 months after TKA, 24 subjects 1 year after unilateral TKA, and 20 control subjects were recruited. All subjects underwent 3D gait analysis. In the TKA groups, the non-operated knee had a higher adduction angle and higher dynamic loading, knee adduction moment and impulse, compared to the operated knee. This increased loading may be an underlying reason for OA progression in the non-operated knee. Measures of loading in the control knee did not differ from that of the non-operated knee in the TKA group, but the TKA group walked with shorter step length. While the non-operated knee loading was not different from controls, there may be greater risk of cumulative loading in the non-operated knee of the TKA group given the shorter step length.

Longitudinal gait and strength changes prior to and following an anterior cruciate ligament rupture and surgical reconstruction: a case report

STUDY DESIGN

Case report.

BACKGROUND

Cross-sectional studies have examined deficits following anterior cruciate ligament (ACL) rupture and subsequent reconstructive surgery. Few studies present preinjury data that may assist in identifying risk factors for ACL rupture. This case report compares gait and strength measures obtained prior to ACL rupture, with follow-up assessments of these measures after rupture and reconstructive surgery.

CASE DESCRIPTION

A 23-year-old woman sustained a noncontact rupture of her right ACL. Kinematic and kinetic gait data were collected using 3-dimensional motion analysis and a synchronized force plate. Knee strength was measured using an isokinetic dynamometer. Data for knee active range of motion (AROM) and the Lower Extremity Functional Scale (LEFS) were also collected. The analyses were descriptive and interpreted based on previously published minimal detectable change and minimal clinically important difference values.

OUTCOMES

Before her injury, the patient demonstrated a low external knee flexion moment during gait. Kinematic and kinetic gait abnormalities were present following rupture and persisted at 13 months postsurgery. The patient demonstrated knee strength deficits following ACL rupture and surgery. Steady gains in LEFS and knee AROM occurred following rupture and surgery.

DISCUSSION

Preinjury data may identify risk factors for ACL rupture. Future studies should examine whether a low external knee flexion moment during gait or sport-related activity is a risk factor for ACL rupture. The patient demonstrated deficits in gait and strength that persisted at 13 months postsurgery.

LEVEL OF EVIDENCE

Therapy, level 4.