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.

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.

Altered gait kinematics and kinetics are observed in patients with medial compartment knee osteoarthritis. Although various kinematic adaptations are proposed to be compensatory mechanisms that unload the knee, the nature of these mechanisms is presently unclear. We hypothesized that an increased toe-out angle during early stance phase of gait shifts load away from the knee medial compartment, quantified as the external adduction moment about the knee. Specifically, we hypothesized that by externally rotating the lower limb anatomy, primarily about the hip joint, toe-out gait alters the lengths of ground reaction force lever arms acting about the knee joint in the frontal and sagittal planes and transforms a portion of knee adduction moment into flexion moment. To test this hypothesis, gait data from 180 subjects diagnosed with medial compartment knee osteoarthritis were examined using two frames of reference. The first frame was attached to the tibia (reporting actual toe-out) and the second frame was attached to the laboratory (simulating no-toe-out). Four measures were compared within subjects in both frames of reference: the lengths of ground reaction force lever arms acting about the knee joint in the frontal and sagittal planes, and the adduction and flexion components of the external knee moment. The mean toe-out angle was 11.4 degrees (S.D. 7.8 degrees , range -2.2 degrees to 28.4 degrees ). Toe-out resulted in significant reductions in the frontal plane lever arm (-6.7%) and the adduction moment (-11.7%) in early stance phase when compared to the simulated no-toe-out values. These reductions were coincident with significant increases in the sagittal plane lever arm (+33.7%) and flexion moment (+25.0%). Peak adduction lever arm and moment were also reduced significantly in late stance phase (by -22.9% and -34.4%, respectively) without a corresponding increase in sagittal plane lever arm or flexion moment. These results indicate that toe-out gait in patients with medial compartment knee osteoarthritis transforms a portion of the adduction moment into flexion moment in early stance phase, suggesting that load is partially shifted away from the medial compartment to other structures.

Measures of frontal plane lower limb alignment obtained from static radiographs and dynamic gait analysis.

Currently, lower limb alignment is measured statically from radiographs that may not accurately represent the condition of the limb when moving and weight-bearing. Thus, the purpose of the present study was to introduce and examine a novel measure of dynamic lower limb alignment obtained during walking in patients with knee OA. In this cross-sectional study, standing, full-length lower limb radiographs were acquired from 80 individuals with confirmed knee OA, who also underwent three-dimensional gait analyses with reflective markers placed on the segments of the lower limb. Frontal plane lower limb alignment was measured using the static radiographs (mechanical axis) and gait analyses (marker-based alignment) by identifying the centres of the hip, knee, and ankle from both methods. Simple linear regression indicated these measures were highly correlated (r=0.84), however, 30% of the variance in the marker-based measure of lower limb alignment was not explained by the mechanical axis despite using the same anatomical landmarks. Results from this study suggest that a valid measure of dynamic lower limb alignment can be obtained from a standard quantitative gait analysis and highlight the differences in measures of lower limb alignment obtained in static and dynamic situations. Future research into the clinical utility of measures of dynamic alignment in the treatment of OA may aid in the development of interventions specifically tailored to one's dynamic lower limb biomechanics during gait.

Radiographic measures of knee alignment in patients with varus gonarthrosis: effect of weightbearing status and associations with dynamic joint load.

BACKGROUND: Radiographic measures of lower limb malalignment are used to indicate abnormal loading of the knee and to plan corrective procedures. HYPOTHESES: Weightbearing status during hip-to-ankle radiographs will significantly affect malalignment measures; malalignment in single-limb standing will be most highly correlated to the external knee adduction moment during gait, a proposed dynamic measure of functional knee joint load. STUDY DESIGN: Controlled laboratory study. METHODS: Mechanical axis angle was measured in 40 patients with varus gonarthrosis from hip-to-ankle radiographs taken with patients in single-limb standing, double-limb standing, and supine positions. Kinematic and kinetic data were collected during walking and used to calculate the peak adduction moment about the knee. RESULTS: Repeated-measures analysis of variance and Scheffé post hoc tests indicated that mechanical axis angle measured on single-limb standing radiographs (-8.7 degrees +/- 4.0 degrees) was significantly greater than on double-limb standing radiographs (-7.1 degrees +/- 3.8 degrees), which was significantly greater than on supine radiographs (-5.5 degrees +/- 2.8 degrees). The peak knee adduction moment (2.8 +/- 0.8 percentage body weight x height) was only moderately correlated with mechanical axis angle on single-limb standing (r = -0.46), double-limb standing (r = -0.45), and supine (r = -0.43) radiographs. CONCLUSION: Patient position significantly affects frontal plane knee alignment. However, the peak knee adduction moment is only moderately correlated to mechanical axis angle, regardless of weightbearing status. CLINICAL RELEVANCE: These findings are inconsistent with the hypothesis that mechanical axis angle measured in single-limb standing is more representative of dynamic joint load and further highlight the differences between static and dynamic measures. Results also underscore the importance of reporting patient position during radiographs and keeping positions consistent when evaluating patients over time.

Knee loading patterns of the non-paretic and paretic legs during post-stroke gait.

BACKGROUND: Post-stoke gait disorders could cause secondary musculoskeletal complications associated with excessive repetitive loading. The study objectives were to 1) determine the feasibility of measuring common proxies for dynamic medial knee joint loading during gait post-stroke with external knee adduction (KAM) and flexion moments (KFM) and 2) characterize knee loading and typical load-reducing compensations post-stroke. METHODS: Participants with stroke (n=9) and healthy individuals (n=17) underwent 3D gait analysis. The stroke and healthy groups were compared with unpaired t-tests on peak KAM and peak KFM and on typical medial knee joint load-reducing compensations; toe out and trunk lean. The relationship between KAM and load-reducing compensations in the stroke group were investigated with Spearman correlations. RESULTS: Mean (SD) values for KAM and KFM in the healthy group[KAM=2.20 (0.88)%BW*ht; KFM=0.64 (0.60)%BW*ht] were not significantly different from the values for the paretic [KAM=2.64 (0.98)%BW*ht; KFM=1.26 (1.13)%BW*ht] or non-paretic leg of the stroke group[KAM=2.23(0.62)%BW*ht; KFM=1.10 (1.20)%BW*ht]. Post hoc one sample t-tests revealed greater loading in stroke participants on the paretic (n=3), non-paretic (n=1) and both legs (n=2) compared to the healthy group. The angle of trunk lean and the angle of toe out were not related to KAM in the stroke group. DISCUSSION: Measurement of limb loading during a gait post-stroke is feasible and revealed excessive loading in individuals with mild to moderate stroke compared to healthy adults. Further investigation of potential joint degeneration and pain due to repetitive excessive loading associated with post-stroke gait is warranted.

Comparison of Gait Characteristics Between Patients With Nontraumatic and Posttraumatic Medial Knee Osteoarthritis.

OBJECTIVE: To compare knee kinematics and kinetics during walking in patients with posttraumatic versus nontraumatic medial compartment knee osteoarthritis (OA). METHODS: Participants with medial compartment knee OA were classified as nontraumatic (n = 122) or posttraumatic (n = 93) based on evidence of previous anterior cruciate ligament tear, confirmed arthroscopically. Kellgren/Lawrence severity scores and mechanical axis angle (MAA) were determined from radiographs. Knee flexion and adduction angles and external moments were calculated from gait analysis using a 3-dimensional optical motion capture system and force plate. Peak values were identified and principal component (PC) analysis determined waveform characteristics (PC scores). Linear regression models examined whether the OA group (posttraumatic or nontraumatic) predicted peak values and PC scores after controlling for age, gait speed, and severity. Models were repeated with and without controlling for MAA. RESULTS: The knee OA group was a significant predictor of peak knee adduction angles (P = 0.04) and moments (P = 0.05). Similarly, it was a significant predictor for some knee adduction angle (P = 0.02 to 0.64) and moment (P = 0.02 to 0.25) PC scores. The nontraumatic OA group had higher adduction angles and moments. There were no significant relationships between OA group and knee flexion angles and moments. After controlling for MAA, only one significant relationship remained between knee adduction moment shape characteristics and OA group. CONCLUSION: Frontal plane knee kinematics and kinetics during walking differ between patients with posttraumatic versus nontraumatic medial compartment knee OA, with posttraumatic OA showing relatively decreased adduction.

Reliability of lower limb frontal plane alignment measurements using plain radiographs and digitized images.

This study evaluated the reliability of lower limb frontal plane alignment measures obtained from plain radiographs measured manually and digitized images measured using a custom computer software package (TheHTO Pro; Fowler Kennedy Sport Medicine Clinic, London, Ontario, Canada). Radiographic measurements used in the planning of high tibial osteotomy, including the mechanical axis angle and mechanical axis deviation, were measured on 42 hip-to-ankle radiographs on two separate occasions by two different raters (A.V.S., J.J.D.). Intraclass correlation coefficients (0.96-0.99) indicated excellent agreement between the manual and computer measurements, suggesting both methods can be used interchangeably. Although test-retest and inter-rater reliability tended to be slightly better when using TheHTO Pro, intraclass correlation coefficients were excellent for both methods (0.97-0.99). The standard errors of measurement were <1 degree for mechanical axis angle and <2 mm for mechanical axis deviation, regardless of method or rater. Based on the observed standard errors of measurement, conservative estimates for the error associated with an individual's mechanical axis angle at one point is approximately 1.5 degrees, and the minimal detectable change on reassessment is approximately 2 degrees. The error associated with an individual's mechanical axis deviation at one point is approximately 4 mm, and the minimal detectable change on reassessment is approximately 6 mm. These results suggest that manual and computer measurements of lower limb frontal plane alignment can be calculated with minimal measurement error. However, the small errors associated with both methods should be considered when making clinical decisions.

Toe-out, lateral trunk lean, and pelvic obliquity during prolonged walking in patients with medial compartment knee osteoarthritis and healthy controls.

OBJECTIVE: To compare the time-varying behavior of maximum toe-out angle, lateral trunk lean (over the stance leg), and pelvic obliquity (rise and drop on the swing leg) during prolonged walking in participants with and without medial compartment knee osteoarthritis (OA), and to explore correlations between these gait characteristics and pain. METHODS: Twenty patients with knee OA and 20 healthy controls completed 30 minutes of treadmill walking. Toe-out, trunk lean, pelvic obliquity, and pain were measured at 5-minute intervals. RESULTS: The mean ± SD toe-out angle was significantly smaller (P = 0.04) in patients with knee OA (6.7 ± 2.5 degrees) than in controls (10.3 ± 2.2 degrees). Toe-out changed significantly over time (P = 0.002), but not in a systematic way, and there was no interaction between group and time. The mean ± SD trunk lean was higher (P = 0.03) in patients with knee OA (2.0 ± 1.0 degrees) than in controls (0.7 ± 0.5 degrees). Trunk lean did not change over time and there was no interaction between group and time. There were no differences for pelvic drop. The mean ± SD pelvic rise was higher (P = 0.01) in patients with knee OA (2.8 ± 0.9 degrees) than in controls (1.2 ± 0.8 degrees), but did not change over time and there was no interaction. Patients experienced a small increase in pain (P < 0.001). Trunk lean and pelvic drop were correlated with pain (r = 0.49, P = 0.03 and r = 0.47, P = 0.04, respectively). CONCLUSION: Toe-out and trunk lean are consistently different between individuals with and without medial compartment knee OA during prolonged walking, and patients with greater pain have greater trunk lean. However, over 30 minutes of walking, these gait characteristics remain quite stable, suggesting they are not acute compensatory mechanisms in response to repetitive loading with subtle increases in pain.

In-shoe plantar pressure measurements for patients with knee osteoarthritis: Reliability and effects of lateral heel wedges.

Although plantar pressure measurement systems are being used increasingly during gait analyses to investigate foot orthotics, there is limited information describing test-retest reliability of such measurements. Objectives of this study were to (1) examine the test-retest reliability of lateral heel pressure (LHP) and centre of pressure (COP) during walking with and without lateral heel wedges, and (2) evaluate the effects of 4° and 8° lateral heel wedges on the magnitude of LHP, the pathway of the COP and the peak external knee adduction moment (KAM) in subjects with and without knee osteoarthritis (OA). Twenty-six subjects, 12 patients with knee OA and 14 healthy subjects, were evaluated during three lateral heel wedge conditions (control, 4° and 8°) with standardized footwear. Three-dimensional analyses of gait with optical motion capture, floor-mounted force plate and in-shoe plantar pressure were completed on two occasions. Intraclass correlation coefficients (ICC(2, 1)) for LHP were excellent (0.79-0.83) while ICCs for COP in the medial-lateral and anterior-posterior directions were more variable (0.66-0.86). Reliability was slightly diminished when using heel wedges. Standard errors of measurement suggested considerable day-to-day variability in an individual's measures. Lateral heel wedges significantly (p<0.001) increased LHP, shifted COP anteriorly and laterally, and decreased the KAM. No significant differences were observed between subjects with and without OA. Although the day-to-day variability appears too large to confidently evaluate changes in individual patients, and decreases in reliability with increases in wedge size indicate caution, these results suggest in-shoe measurement of LHP and COP are appropriate for use in studies evaluating biomechanical effects of foot orthoses for knee OA.

Effect of Anterior Tibiofemoral Glides on Knee Extension during Gait in Patients with Decreased Range of Motion after Anterior Cruciate Ligament Reconstruction.

PURPOSE: The purpose of this preliminary investigation was to evaluate the effect of anterior tibiofemoral glides on maximal knee extension and selected spatiotemporal characteristics during gait in patients with knee extension deficits after anterior cruciate ligament (ACL) reconstruction. METHODS: Twelve patients with knee-extension deficits after recent ACL reconstructions underwent quantitative gait analyses immediately before and after 10 minutes of repeated anterior tibiofemoral glides on the operative limb, and again after a 10-minute seated rest period. RESULTS: Maximum knee extension during stance phase of the operative limb significantly increased immediately after the treatment (mean increase: 2.0°±4.1°, 95% CI: 0.6°-3.3°). Maximum knee extension decreased after the 10-minute rest period (mean decrease: 0.9°±1.8°, 95% CI: -0.1°-1.8°), although the decrease was not statistically significant. Small increases in operative limb step length, stride length, and gait speed were observed after the rest period compared to baseline values only. CONCLUSIONS: A single session of anterior tibiofemoral glides increases maximal knee extension during the stance phase of gait in patients with knee-extension deficits. Increases in knee extension are small and short-lived, however, suggesting that continued activity is required to maintain the observed improvements.

Electromyography and kinematics of the trunk during rowing in elite female rowers.

PURPOSE: The purpose of this study was to characterize the EMG of trunk muscles together with kinematics of the pelvis and the spine of elite female rowers during the rowing stroke. METHODS: Nine Rowing Canada national team candidates performed a 2000-m race simulation. EMG activity of spinal and pelvic extensor and flexor muscles and kinematic data of the pelvis and the spine were collected and analyzed during the period of peak force production. RESULTS: During this period, pelvic and spinal extensor muscles demonstrated similarities in the timing of muscle activity with minimal coactivation of flexors and extensors. Minimal excursion of spinal segments occurred during the stroke with most of the extension occurring at the pelvis. Flexor activity occurred toward late drive, suggesting that trunk extension is slowed by increasing activity of the flexor muscles. CONCLUSIONS: This study provides data of trunk kinematics and muscle recruitment patterns in elite female rowers. During the period of peak force production, there is minimal coactivation of trunk flexor and extensor muscles and, of the spinal segments, L3-S1 shows the most movement, which may make it more susceptible to soft tissue injury.

Effect of tibial re-alignment surgery on single leg standing balance in patients with knee osteoarthritis.

BACKGROUND: Standing balance is impaired in individuals with knee osteoarthritis and is associated with disease severity. The effects of surgical interventions on standing balance have received little attention. The purpose of the present study was to examine measures of balance during tests of single-limb standing before and after medial opening wedge high tibial osteotomy--a lower limb re-alignment procedure for those with varus alignment and knee osteoarthritis. METHODS: Standing balance was assessed in 49 individuals prior to and 12 months following medial opening wedge high tibial osteotomy. Participants performed three trials of single-limb balance lasting 10s each while standing on a force platform. Anteroposterior and mediolateral coordinates of the centre of pressure were obtained from the force platform and used to calculate the total centre of pressure path length as well as the range and variability (standard deviation) of the anteroposterior and mediolateral coordinates. FINDINGS: Though all centre of pressure measures were lower following high tibial osteotomy, none reached statistical significance (P>0.05) and effect sizes were small (d<0.34). The largest mean improvement was 7.6% (95% confidence interval: -0.7-15.8%). INTERPRETATION: Results indicate that standing balance in individuals with knee osteoarthritis is not significantly different following high tibial osteotomy surgery. Standing balance in this patient population is a complex process not entirely dictated by disease symptoms or structural factors such as alignment.

Moments and muscle activity after high tibial osteotomy and anterior cruciate ligament reconstruction.

PURPOSES: To evaluate the effects of simultaneous high tibial osteotomy (HTO) and anterior cruciate ligament (ACL) reconstruction on 1) the external knee adduction moment, 2) the external knee flexion and extension moments, and 3) the quadriceps, hamstrings, and gastrocnemius muscle activity during walking. METHODS: Twenty-one patients with varus malalignment of the lower limb, medial compartment knee osteoarthritis, and concomitant anterior cruciate ligament (ACL) deficiency were tested before and 1 yr after undergoing simultaneous medial opening wedge high tibial osteotomy (HTO) and ACL reconstruction during a single operation. Three-dimensional kinetic and kinematic data were used to calculate external coronal and sagittal moments about the knee. EMG data from the quadriceps, hamstrings, and gastrocnemius were used to determine coactivation ratio and activation patterns. RESULTS: Neutral alignment and knee stability were achieved in all patients after surgery. The peak knee adduction moment decreased from 2.88 +/- 0.57 to 1.71 +/- 0.56%BW x Ht (P < 0.001). The early stance knee flexion moment decreased from 1.95 +/- 1.89 to 0.88 +/- 1.17%BW x Ht (P < 0.01). The late stance knee extension moment increased from 1.83 +/- 1.53 to 2.76 +/- 1.22%BW x Ht (P < 0.001). There were no significant differences in muscle coactivation or muscle activation patterns (P > 0.05). CONCLUSIONS: Improving lower limb alignment and knee stability significantly alters the coronal and the sagittal moments about the knee during walking, without apparent changes in muscle activation patterns.

Resistance training for medial compartment knee osteoarthritis and malalignment.

PURPOSES: 1) To evaluate the effects of a 12-wk high-intensity knee extensor and flexor resistance training program on strength, pain, and adherence in patients with advanced knee osteoarthritis and varus malalignment and 2) to generate pilot data for change in dynamic knee joint load, patent-reported outcomes, and self-efficacy after training. METHODS: Fourteen patients (48.35 +/- 6.51 yr) with radiographically confirmed medial compartment knee osteoarthritis and varus malalignment of the lower limb were recruited from a surgical waiting list for high tibial osteotomy. Participants completed a high-intensity isokinetic resistance training program three times per week for 12 wk. Knee extensor and flexor strength were assessed every third week, whereas pain and adherence were recorded at every training session. The external knee adduction moment during the gait, the 6-min-walk test, the Knee Injury and Osteoarthritis Outcome Score (KOOS), and the Arthritis Self-Efficacy Scale (ASES) were also evaluated before and after training. RESULTS: Significant improvements in knee extensor and flexor strength were observed without increases in pain during or after training. Adherence to the high-intensity program was high. No significant changes were observed for dynamic knee joint load or the KOOS. There was a significant increase in the function subscale of the ASES only. CONCLUSIONS: These findings suggest that patients with advanced knee osteoarthritis and malalignment can experience substantial gains in strength after a high-intensity resistance training program without concomitant increases in pain, adverse events, or compromised adherence. These findings provide support for future clinical trials with longer-term outcomes.

Test-retest reliability of the peak knee adduction moment during walking in patients with medial compartment knee osteoarthritis.

OBJECTIVE: To estimate the test-retest reliability of the peak external knee adduction moment during walking in patients with medial compartment knee osteoarthritis (OA), and to describe the interpretation of the reported values. METHODS: A total of 31 patients diagnosed with knee OA confined primarily to the medial compartment underwent quantitative gait analyses during 2 separate test sessions at least 24 hours apart and within 1 week. The peak knee adduction moment was calculated for each patient at each session based on the mean of 5 walking trials. Reliability was estimated using the intraclass correlation coefficient (ICC(2,1)) and the standard error of measurement (SEM). RESULTS: The mean difference in peak adduction moments between test sessions was 0.1% body weight x height (BW x ht; 95% confidence interval [95% CI] -0.1, 0.3). The point estimate for the ICC was 0.86 (95% CI 0.73, 0.96). The point estimate for the SEM was 0.36% BW x ht (95% CI 0.29, 0.48). CONCLUSION: The ICC suggests that the peak knee adduction moment is appropriate for use when distinguishing among patients, for example, in studies of various interventions intended to decrease dynamic load on the knee medial compartment. The SEM illustrates the importance of considering measurement error and incorporating confidence levels when interpreting an individual patient's peak knee adduction moment value.

1H and 13C NMR data to aid the identification and quantification of residual solvents by NMR spectroscopy.

We present reference data and a javascript web page which allow the rapid identification and quantification of residual solvents by NMR. The data encompass all of the ICH-prescribed solvents and were obtained for a number of NMR solvents. We also present an example of its application.

Automated structure elucidation of two unexpected products in a reaction of an alpha,beta-unsaturated pyruvate.

The reaction between an alpha,beta-unsaturated pyruvate and ethyl diazoacetate (EDA) yielded two unexpected products. The structures of these products were determined by automated elucidation of the chemical structures using spectroscopic inputs of a series of 1D and 2D NMR data using the computer program ACD/Structure Elucidator, StrucEluc. The formation of these products is rationalised. Their structures were also confirmed by x-ray crystallography.