Diminished Vibration Perception and Greater Pressure Pain Sensitivity are Associated with Worse Knee Osteoarthritis Outcomes across Sex and Race.

OBJECTIVE: To examine associations of vibration sensitivity and pressure pain sensitivity with knee osteoarthritis (OA) outcomes across sex and race, which may relate to known sex and race disparities in clinical outcomes. DESIGN: Data were from the 2013-2015 visit of the Johnston County Osteoarthritis Project. Exposures were vibration perception threshold (VPT) measured at the bilateral medial femoral condyle (MFC) and first metatarsophalangeal joint (MTP), and pressure pain threshold (PPT) measured at the bilateral upper trapezius. Outcomes were knee pain severity and presence of knee symptoms, radiographic knee OA, and symptomatic knee OA in each knee. Cross-sectional associations of the exposures with the outcomes were examined using logistic regression models, overall and separately by sex and race. RESULTS: In the VPT and PPT analyses, 851 and 862 participants (mean age 71 years, 68% female, 33% Black, body mass index 31 kg/m2) and 1585 and 1660 knees were included, respectively. Higher VPT (lower vibration sensitivity) at the MFC and first MTP joint was associated with all outcomes. Lower PPT (greater pressure pain sensitivity) was associated with greater knee pain severity. Associations of VPT and PPT with all outcomes were similar among females and males and Black and White individuals. CONCLUSIONS: Diminished vibration perception and greater pressure pain sensitivity were cross-sectionally associated with worse knee OA outcomes. Despite differences in VPT and PPT among females and males and Black and White adults, associations with knee OA outcomes did not differ by sex or race, suggesting neurophysiological differences do not relate to established disparities.

Gait speed and kinesiophobia explain physical activity level in adults with osteoarthritis: A cross-sectional study.

Identifying potential contributing factors for physical inactivity in people with knee osteoarthritis is vital for designing practical activity promoting interventions. Walking is a common activity, but it is unknown how gait characteristics may influence physical activity and if psychological factors, specifically fear of movement (kinesiophobia), contribute to this relationship. The aim of our study was to investigate the contributions of select gait parameters and kinesiophobia to activity levels. Cross-sectional data from 40 participants (F 24|M 16; age 57.6 ± 8.9 years; BMI 34.7 ± 7.0 kg/m2 ) with uni- or bilateral knee osteoarthritis were included. Physical activity and kinesiophobia were assessed by self-report using the University of California, Los Angeles activity rating scale, and Tampa scale for kinesiophobia, respectively. Gait parameters were collected with three-dimensional gait analysis while participants walked on an instrumented split-belt treadmill at a self-selected speed. Higher peak sagittal plane joint moments at the ankle (ρ = 0.418, p = 0.007), and hip (ρ = 0.348, p = 0.028), faster self-selected gait speed (ρ = 0.553, p < 0.001), and less kinesiophobia or fear of movement (ρ = -0.695, p < 0.001) were independently related to higher physical activity level in adults with knee osteoarthritis. In hierarchical regression models, after accounting for covariates, only self-selected gait speed, and kinesiophobia significantly contributed to explaining the variation in physical activity level. Statement of clinical significance: Interventions aimed at improving physical activity participation in those with lower limb osteoarthritis should consider assessing the contribution of pain-related fear of movement.

Sagittal plane ankle kinetics are associated with dynamic hip range of motion and gait efficiency in women with hip osteoarthritis.

Loss of sagittal plane hip range of motion (ROM) is a commonly reported walking gait impairment in people with hip osteoarthritis (OA). The purpose of this study was to evaluate whether sagittal plane hip ROM reduction and the resulting altered sagittal plane ankle kinetics during gait influence the energy cost of walking in people with hip OA. We evaluated 24 women with unilateral hip OA (60 ± 9.1 years; 29.4 ± 6.1 kg/m2 ). Sagittal plane hip ROM and peak ankle dorsiflexion moment were assessed by instrumented gait analysis. We also used a portable metabolic system to measure the energy cost of walking. Pearson correlations and regression analyses were performed to test our hypotheses. We found that greater involved limb sagittal plane hip ROM was associated with a larger ankle peak dorsiflexion moment at push-off during gait (R = 0.50, p = 0.01). Greater involved limb peak ankle dorsiflexion moment at push-off was associated with a lower oxygen consumption during gait (R = -0.51, p = 0.01). Involved limb peak ankle dorsiflexion moment at push-off predicted 26% of the variance in O2 cost. Statement of Clinical Significance: Sagittal plane hip ROM was associated with peak ankle dorsiflexion moment at push-off during gait in women with hip OA. Moreover, peak ankle dorsiflexion moment at push-off was associated with the energy cost of walking. Therefore, modifying sagittal plane hip ROM and peak ankle dorsiflexion moment could be a possible rehabilitation strategy to improve gait efficiency in women with hip OA.

Strength and physical activity in osteoarthritis: The mediating role of kinesiophobia.

The aim of this study was to investigate the association between muscle strength and physical activity level in people with knee osteoarthritis (OA), and determine whether this association is mediated by pain-related fear of movement (kinesiophobia) and self-reported pain. Cross-sectional data from 37 subjects (age 58.8 ± 8.6 years, 25F/12M, BMI 33.5 ± 6.4 kg/m2 ) with OA of the knee were used. Isometric knee extensor and flexor muscle strength were measured using an isokinetic dynamometer. Physical activity, kinesiophobia, and pain were assessed by self-report using the University of California, Los Angeles activity rating scale, Tampa Scale for Kinesiophobia, and The Knee Injury and Osteoarthritis Outcome Score pain subscale, respectively. The associations between strength measures, physical activity, kinesiophobia, and pain scores, were modeled by performing a parallel multiple mediation analysis and the significance of mediational effects (kinesiophobia and pain) were tested using a bootstrap approach. Lower knee flexion and extension strength were associated with lower physical activity scores and these relationships were mediated by higher kinesiophobia scores (more fear) but not pain scores. Knee extension strength was directly associated with physical activity scores after controlling for kinesiophobia and pain scores. These results suggest that muscle strength can influence physical activity directly and indirectly through fear of movement. Assessing these measures together in this population may help clinicians identify patients that are more likely to avoid physical activities due to not only muscle weakness but also fear of movement.

Impact of step length asymmetry on walking energetics in women with hip Osteoarthritis: A pilot study.

A step length difference between the involved and uninvolved limbs in participants with hip osteoarthritis (OA) has been reported. The implications of step length asymmetry on other aspects of walking mechanics are as yet unknown. The objective of the current study was to evaluate the consequences of step length asymmetry on motion of the center of mass (COM) and energy cost of walking. We hypothesized that (i) increased step length asymmetry is associated with decreased mechanical energy exchange; (ii) decreased mechanical energy exchange is associated with increased O2 cost; (iii) increased step length asymmetry is associated with increased oxygen O2 cost during walking in women with hip OA. We evaluated 24 women with unilateral hip OA using motion analysis as participants walked on a treadmill at self-selected speeds. Kinematic data were collected to compute step length asymmetry and mechanical energy exchange through the motion of COM. We also used a portable metabolic system to measure the energy cost of walking simultaneously. We used Pearson correlations and linear regression to test our hypotheses. We found that more asymmetric step lengths were associated with lower mechanical energy exchange (R2 = 0.231, p = 0.017). More mechanical energy exchange was associated with lower O2 cost during gait (R2 = 0.284, p = 0.009). Mechanical energy exchange predicted 54.5% of the variance in O2 cost after adjusting for self-selected walking speed. Findings suggest that modifying step length asymmetry could enhance metabolic gait efficiency indirectly by improving mechanical energy exchange in participants with hip OA.

Walking energetics and fatigue are associated with physical activity in people with knee osteoarthritis.

BACKGROUND: Aberrant biomechanics may influence osteoarthritis-associated physical activity limitations. Our purpose was to evaluate the association of walking energetics, fatigue, and fatigability on physical activity in people with knee osteoarthritis. We hypothesized that using increased energy for walking, experiencing more fatigue, or being more fatigable are associated with less activity, and that fatigue and fatigability mediate the relationships between walking energetics and physical activity. METHODS: We tested our hypothesis in 30 people with knee osteoarthritis (age 58 ± 9 years, 10 Male/20 Female). Physical activity was assessed using the University of California Los Angeles score. We used a six-minute walk test to predict VO2max. Next we used a portable oxygen exchange system to measure relative energy used (100 * VO2rate/VO2max) and VO2cost during walking at preferred speeds. We used the Knee injury and Osteoarthritis Outcome Score subscale to quantify pain, and the Patient Reported Outcome Measurement Instrument System Fatigue survey and a treadmill-based fatigability test to assess fatigue and fatigability. Spearman correlations, regression, and mediation analysis were used to test our hypotheses. FINDINGS: Greater energy used during walking, fatigue, and fatigability were all associated with lower physical activity (rho = -0.585 to -0.379, P = 0.001 to 0.043). These associations persisted when incorporating pain into the models. Fatigue and fatigability mediated the associations between walking energetics and physical activity. INTERPRETATION: Walking energetics could be a useful target to promote physical activity in people with osteoarthritis. Further, the effect of walking energetics on physical activity may work through its impact on fatigability.

Walking energetics and abductor strength are associated with physical activity in older women with hip osteoarthritis.

BACKGROUND: Osteoarthritis (OA) can hinder physical activity in older adults for reasons that are not fully understood. Functional barriers may exist such as reduced muscle strength around the affected joint, potentially affecting physical activity. Aging-associated declines in energy capacity may also be exacerbated by OA. These factors may work together to influence physical activity in people with OA. RESEARCH QUESTION: Our objective was to evaluate the combined role of walking energetics and hip abductor strength on physical activity in older women with hip OA. METHODS: We evaluated 30 women with moderately symptomatic hip OA (61 ± 10 yrs; 30.7 ± 4.9 kg/m2) in this cross-sectional observational study. We measured physical activity using the UCLA activity score and quantified activity frequency and intensity using accelerometers worn for seven days (7 ± 2 days). We used a portable oxygen exchange system to measure energy used during walking at preferred speeds (relative to total energy capacity assessed using a six-minute walk test) and a dynamometer to measure hip abductor strength. We used Pearson correlations and regression analysis to test our hypotheses. RESULTS: Greater energy used during walking was associated with lower self-reported physical activity (R=-0.626, p < 0.001), more sedentary time (R = 0.567, p = 0.002), and less light activity time (R=-0.644, p < 0.001). Lower hip abductor strength was associated with lower self-reported physical activity (R = 0.406, p = 0.039). While there was no association between hip abductor strength and energy used during walking, together these variables predicted 55.5 % of the variance in self-reported physical activity. SIGNIFICANCE: Results suggest intervention targets to promote physical activity in this population.

Aerobic capacity and fatigability are associated with activity levels in women with hip osteoarthritis.

Physical activity is important for physical function and pain relief in people with lower extremity osteoarthritis (OA). Unfortunately, people with OA are not as active as their peers without OA. The objective of this study was to determine whether aerobic capacity and fatigability are associated with physical activity in women with hip OA. We conducted a cross-sectional analysis of 36 women with hip OA. We assessed aerobic fitness as predicted VO2 max from a 6-min walk test. We assessed fatigability using a treadmill test. Finally, we assessed self-reported physical activity using the UCLA activity scale and quantified steps per day and activity intensity using accelerometers. We used Pearson correlations to determine associations. We used regression analysis to determine whether fatigability mediated the association between aerobic fitness and physical activity. On average, subjects were moderately active via the UCLA score (5.2 ± 1.3 out of 10). Aerobic fitness (R = 0.582, p < .001) and fatigability (R = 0.516, p =.003) were significantly correlated with UCLA scores. However, aerobic fitness was the best predictor of UCLA scores, as well as sedentary time, and time spent in light activity. Fatigability was not a mediator between aerobic fitness and UCLA scores. Aerobic fitness and fatigability may be modifiable barriers to physical activity in people with OA. Future interventional studies should examine whether improving aerobic fitness improves physical activity or fatigability.

Task-Specific Perturbation Training Improves the Recovery Stepping Responses by Women With Knee Osteoarthritis Following Laboratory-Induced Trips.

Trip-specific training improves the kinematics of trip-specific compensatory stepping response (CSR) in the laboratory and reduces prospectively measured trip-related fall-rate of middle age and older women. We examined whether one session of trip-specific perturbation training could improve recovery step kinematics in women with knee osteoarthritis (OA), a condition known to increase fall risk. Seventeen women with self-reported symptomatic knee OA (age 61.1 ± 7.7 years, body mass index [BMI] 29.7 ± 5.9 kg/m2 ) and 22 control women (age 59.5 ± 6.8 years, BMI 28.4 ± 6.2 kg/m2 ) completed a brief training protocol consisting of 20 trials of treadmill-delivered trip-specific perturbations. We assessed pre- and post-training recovery step length and trunk kinematics at the instant of recovery step completion. Repeated-measures analysis of variance was used to determine the significance of between-group differences following the training protocol, and to evaluate the significance of within-group pre-to-post changes in the variables of interest. The group by training interaction effects for step length (p = 0.466), trunk flexion angle (p = 0.751), and trunk angular velocity (p = 0.413) were not significant and the pre-to-post changes in step length were not significant (p = 0.286). However, pre-to-post trunk flexion angle improved by 26% and 34% in the OA and control groups, respectively (p < 0.001) and trunk flexion angular velocity decreased by 193% in the OA group and by 32% in the control group, respectively (p < 0.001), often reflecting a transition to the direction of extension. The results suggest that trip-specific training can improve CSR kinematics in women with knee OA. It is important to determine, the effectiveness of trip-specific training in decreasing trip-specific fall-rate by women with knee OA. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:663-669, 2020.

Hip joint moments in symptomatic vs. asymptomatic people with mild radiographic hip osteoarthritis.

Our primary objective was to examine external hip joint moments during walking in people with mild radiographic hip osteoarthritis (OA) with and without symptoms and disease-free controls. Three groups were compared (symptomatic with mild radiographic hip OA, n = 12; asymptomatic with mild radiographic hip OA, n = 13; OA-free controls, n = 20). Measures of the external moment (peak and impulse) in the sagittal, frontal and transverse plane during walking were determined. Variables were compared according to group allocation using mixed linear regression models that included individual gait trials, with group allocation as fixed effect and walking speed as a random effect. Participants with evidence of radiographic disease irrespective of symptoms walked 14-16% slower compared to disease-free controls (p = 0.002). Radiographic disease without symptoms was not associated with any altered measures of hip joint moment compared to asymptomatic OA-free controls once speed was taken into account (p ≥ 0.099). People with both mild radiographic disease and symptoms had lower external peak hip adduction moment (p = 0.005) and lower external peak internal rotation moment (p < 0.001) accounting for walking speed. Among angular impulses, only the presence of symptoms was associated with a reduced hip internal rotation impulse (p = 0.002) in the symptomatic group. Collectively, our observations suggest that symptoms have additional mechanical associations from radiographic disease alone, and provide insight into potential early markers of hip OA. Future research is required to understand the implications of modifying walking speed and/or the external hip adduction and internal rotation moment in people with mild hip OA.

Static and dynamic abductor function are both associated with physical function 1 to 5 years after total hip arthroplasty.

BACKGROUND: A subset of total hip arthroplasty patients experience functional impairments past the first postoperative year. Poor hip abductor function is common before and in the early postoperative period. It is not known if abductor impairment is associated with long-term functional impairment. This study evaluated the relationships between static and dynamic abductor function and performance-based and self-reported function >1 year post-total hip arthroplasty. METHODS: Eighteen adults 1-5 years post-total hip arthroplasty participated. Static and dynamic abductor function were assessed through dynamometry and gait analysis, respectively. Subjects completed four physical performance tests and two self-report instruments. FINDINGS: Higher peak isometric abductor strength was associated with better performance-based function (P ≤ 0.001-0.030) and with self-reported function (P ≤ 0.001-0.012). Higher peak external adduction moment was associated with better results on 3 of 4 performance tests (P = 0.007-0.026). Together, static and dynamic abductor function predicted 35-77% of the variation in physical function. Abductor strength best predicted walking test results and self-reported function, while dynamic abductor function best predicted tests involving sit-to-stand INTERPRETATION: Static and dynamic abductor function were associated with physical function 1-5 years after total hip arthroplasty. These results support further investigation of interventions targeting abductor function for persons experiencing persistent impairments.

Step Length Asymmetry and Its Associations With Mechanical Energy Exchange, Function, and Fatigue After Total Hip Replacement.

Abnormalities in gait remain after total hip replacement (THR). The purpose of this study was to evaluate step length asymmetry and its links to other aspects of gait and physical function after THR and to investigate links with mechanical energy exchange. The rationale is that step length asymmetry may influence gait efficiency, which could adversely influence fatigue and physical function. We evaluated 18 participants (6 males and 12 females) 1-5 years post-THR. Step length symmetry and mechanical energy exchange were assessed by instrumented gait analysis. Fatigue was assessed using a PROMIS Fatigue Short Form. We assessed physical function using a 6-minute walk test (6MWT). We used a one sample T test to determine whether the symmetry index (SI) was significantly different from 0 and Pearson's correlations to explore associations among the variables. The step length SI was statistically significantly different from zero (p=0.01). A more symmetric step length was associated with better 6MWT (R=-0.57, p=0.03). Higher (better) mechanical energy exchange was associated with more fatigue (R=0.50, p=0.04). Mechanical energy exchange was not associated with step length SI or 6MWT. Better 6MWT was associated with less fatigue (R=-0.61, P=0.01). This suggests that the association between step length symmetry and function is not directly governed by its effect on the energy exchange. Additionally, after a relatively long period of postsurgery, participants may have adapted their gait by increasing mechanical energy exchange to minimize fatigue. Statement of Clinical Significance: A gait retraining intervention targeting step length symmetry could improve function without adversely affecting walking energetics in THR patients. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1563-1570, 2019.

Gait asymmetries in unilateral symptomatic hip osteoarthritis and their association with radiographic severity and pain.

INTRODUCTION:: Little is known about the loading patterns in unilateral hip osteoarthritis (OA) and their relationship to radiographic severity and pain. We aimed to examine the loading patterns at the hips of those with unilateral symptomatic hip OA and identify associations between radiographic severity and pain with loading alterations. METHODS:: 61 subjects with symptomatic unilateral hip OA underwent gait analyses and evaluation for radiographic severity (Kellgren-Lawrence [KL]-grade) and pain (visual analogue scale) at bilateral hips. RESULTS:: Hip OA subjects had greater range of motion and higher hip flexion, adduction, internal and external rotation moments at the contralateral, asymptomatic hip compared to the ipsilateral hip ( p < 0.05). Correlations were noted between increasing KL-grade and increasing asymmetry of contralateral to ipsilateral hip loading ( p < 0.05). There were no relationships with pain and loading asymmetry. DISCUSSION:: Unilateral symptomatic hip OA subjects demonstrate asymmetry in loading between the hips, with relatively greater loads at the contralateral hip. These loading asymmetries were directly related to the radiographic severity of symptomatic hip OA and not with pain. CONCLUSION:: Additional research is needed to determine the role of gait asymmetries in disease progression.

Hypoesthesia after anterior cruciate ligament reconstruction: The relationship between proprioception and vibration perception deficits in individuals greater than one year post-surgery.

BACKGROUND: While surgical reconstruction restores mechanical stability following anterior cruciate ligament (ACL) rupture, many experience early-onset osteoarthritis despite surgery. Neurophysiological changes are hypothesized to contribute to knee osteoarthritis progression. Proprioceptive deficits have been reported following ACL injury/reconstruction; however, vibration perception threshold (VPT) has been less studied. This study explored relationships between pain, VPT, proprioception, function, and strength following ACL-reconstruction. METHODS: Twenty individuals (27 ±â€¯6 years; 10 males) (standard deviation) status-post ACL-reconstruction were compared with a control group. Measurements included VPT, proprioception (threshold to detect passive movement), pain, function (Knee Outcome Survey (KOS)) and isometric quadriceps strength. Group differences were assessed using Mann-Whitney U tests, side-to-side differences with Wilcoxon Signed Rank tests, and associations evaluated using Spearman correlations. RESULTS: The ACL-reconstruction group had minor functional deficits (15 ±â€¯11%) and resting pain (1.8 ±â€¯1.7). Impaired VPT and proprioception (hypoesthesia) were demonstrated on surgical compared to contralateral and control limbs (p ≤ 0.008). Proprioception was significantly different between contralateral and control knees, but not VPT. Surgical knee proprioceptive deficits and VPT deficits were positively correlated (ρ = 0.462, p = 0.047) but not in controls (ρ = -0.042, p = 0.862). Strength was negatively correlated to pain (ρ = -0.589; p = 0.006), but not to KOS scores, proprioception or VPT (p ≥ 0.099). CONCLUSION: Proprioceptive deficits following ACL injury have been ascribed to loss of afferent input from the torn ligament. Alternatively, multi-modality as well as contralateral sensory deficits suggest a spinal/supraspinal source of neurophysiological findings which may predispose to early osteoarthritis. LEVEL OF EVIDENCE: III.

Duration of symptoms is associated with conditioned pain modulation and somatosensory measures in knee osteoarthritis.

Impaired descending pain inhibition has been linked to chronic pain and poorer patient outcomes. Vibration perception threshold (VPT) has also been observed and linked to radiographic stage of OA. However, it is not known how duration of symptoms may influence these neurophysiological measures. Our purpose was to evaluate the relationship between duration of symptoms and conditioned pain modulation (CPM), a measure of descending pain inhibition, and VPT, and to determine whether these relationships differed in men and women seeking orthopedic care. We evaluated 18 men and 27 women with moderate to severe knee OA. We assessed CPM using a submaximal-effort tourniquet test: Pressure pain threshold (PPT) at the symptomatic knee was evaluated before and after a noxious stimulus. CPM impairment was indicated by a ratio of pre-to-post stimulus PPT ≥1. VPT was assessed using a biothesiometer at the medial femoral condyle. We used chi-square, t-tests and Pearson correlations to address study questions. 72% of men, but only 44% of women had CPM impairment. Duration of symptoms was associated with CPM impairment in women (R = 0.566, p = 0.003) but not men (R = 0.366, p = 0.135). Duration of symptoms was also associated with VPT in both men (R = 0.580, p = 0.012) and women (R = 0.406, p = 0.039). These results suggest that longer duration of knee OA may predict more severe pain sensitization and that important sex differences exist in descending pain inhibition in people with chronic knee OA that may affect disease and course of treatment in male and female patients. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Sex specific associations between biomechanical recovery and clinical recovery after total hip arthroplasty.

BACKGROUND: There are sex-specific gait differences in men and women before and after total hip arthroplasty (THA) but we do not know their impact on clinical outcomes. The objective of this study was to identify sex-specific associations between pre- and postoperative changes in pain and function and (i) gait mechanics, (ii) passive range of motion, and (iii) abductor strength. METHODS: Pre- and one-year postoperative data were identified from a data repository (n = 124; 64 Women; Age 61 (SD 10); BMI 29 (SD 5)). We used linear regression analysis to identify sex-specific associations between Harris Hip Score pain and function subscores, and sagittal plane hip kinematics and 3D hip kinetics during gait, hip abductor strength, and passive hip range of motion (RoM). FINDINGS: Combinations of biomechanical variables predicted up to 24% of the variation in pain improvement and up to 27% of the variation in functional improvement. In men, increased peak external rotation moments were associated with pain improvement. Passive flexion RoM and peak extension moments were associated with functional improvement. In women, increased passive adduction RoM and peak external rotation moments were associated with pain improvement. Peak adduction moments and passive flexion RoM were associated with functional improvement. INTERPRETATIONS: The different associations between improvement in clinical outcomes and improvement in gait, passive RoM, and abductor strength suggest that the biomechanical path to recovery may be different in men and women.

Inter-joint coordination of kinematics and kinetics before and after total hip arthroplasty compared to asymptomatic subjects.

While differences in joint kinematics and kinetics between control subjects and patients before and after total hip arthroplasty (THA) has often been studied, inter-joint coordination has not been fully characterized. We hypothesized that in patients undergoing THA, inter-joint coordination (i) is different from control subjects before surgery, (ii) changes from pre-operative to post-operative, and (iii) remains different from control subjects after surgery. Seventy-eight subjects underwent gait analysis before and ∼1 year after primary unilateral THA. 109 control subjects were age, sex, and BMI matched to the THA group. We selected a representative trial at each subjects' self-selected walking speed from a motion analysis data repository. To assess kinematic coordination, we constructed sagittal plane hip-knee angle cyclograms, and calculated total, stance, and swing phase plot area (deg2). To assess kinetic coordination, we calculated the support moment (MS, %wt ∗ ht), the time-integral of support moment (MS impulse, %wt ∗ ht ∗ t), and the relative contribution of each joint to MS impulse (%Hip, %Knee, %Ankle). We used t-tests to compare groups. Total and swing-phase cyclogram area was smaller preoperatively, but improved to control values after THA. Swing-phase area was smaller than control values after THA. MS impulse was larger in THA subjects than controls both before and after surgery. While, the relative contribution of the hip to MS impulse was not different from control values, the contributions of the knee and ankle were smaller. Inter-joint coordination, as measured by hip-knee angle cyclograms and MS impulse, may be used to distinguish differences in gait mechanics between osteoarthritis and THA. Future work focusing on coordination among joints may be needed to fully restore gait function.

Hip abductor strength and fatigue are associated with activity levels more than 1 year after total hip replacement.

Despite improvements in pain and function, people who undergo total hip arthroplasty (THR) may not always return to desired levels of physical activity (PA). The factors associated with low activity levels are not fully understood. Abductor weakness and fatigue have both been proposed as factors that limit activity in older adults or people with hip osteoarthritis, but have not been investigated after THR. We hypothesized that abductor weakness and fatigue are associated with lower activity levels in people who have undergone a THR and that fatigue mediates the association between abductor strength and activity. We evaluated 16 subjects (24 ± 10 months post-THR; age 56.8 ± 8.4 yrs; BMI 31 ± 7 kg/m2 ). Fatigue was assessed using the PROMIS fatigue short-form 7a. Peak isometric hip abductor torque was assessed using a dynamometer with subjects in a sidelying position. We assessed activity level using the UCLA activity score. We used Pearson correlations to explore the associations among the variables. Next we used a three-step linear regression procedure to test whether or not fatigue acted as a mediator between abductor torque and UCLA activity scores. Higher abductor torque was associated with less fatigue (R2 = 0.275; p = 0.037) and with higher UCLA scores (R2 = 0.488, p = 0.003). Higher fatigue was associated with lower UCLA scores (R2 = 0. 307, p = 0.017), however there was no evidence of mediation. This suggests that addressing both abductor strength and fatigue may increase physical activity. Statement of Clinical Significance: Fatigue and abductor weakness should be evaluated in sedentary THR patients presenting for long-term follow-up. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1519-1525, 2018.

Sex-specific hip osteoarthritis-associated gait abnormalities: Alterations in dynamic hip abductor function differ in men and women.

BACKGROUND: Hip osteoarthritis results in abnormal gait mechanics, but it is not known whether abnormalities are the same in men and women. The hypothesis tested was that gait abnormalities are different in men and women with hip osteoarthritis vs. sex-specific asymptomatic groups. METHODS: 150 subjects with mild through severe radiographic hip osteoarthritis and 159 asymptomatic subjects were identified from an Institutional Review Board-approved motion analysis data repository. Sagittal plane hip range of motion and peak external moments about the hip, in all three planes, averaged from normal speed walking trials, were compared for men and women, with and without hip osteoarthritis using analysis of variance. FINDINGS: There were significant sex by group interactions for the external peak hip adduction and external rotation moments (P=0.009-0.045). Although asymptomatic women had peak adduction and external rotation moments that were respectively 12% higher and 23% lower than asymptomatic men (P=0.026-0.037), these variables did not differ between men and women with hip osteoarthritis (P≥0.684). The osteoarthritis vs. asymptomatic group difference in the peak hip adduction moment was 45% larger in women than in men. The osteoarthritis vs. asymptomatic group difference in the peak hip external rotation moment was 55% larger for men than for women (P<0.001). Sex did not influence the association between radiographic severity and gait variables. INTERPRETATION: Normal sex differences in gait were not seen in hip osteoarthritis. Sex-specific adaptations may reflect different aspects of hip abductor function. Men and women with hip osteoarthritis may require different interventions to improve function.