Knee Osteoarthritis Subjects Research Articles

Knee internal contact force in a varus malaligned phenotype in knee osteoarthritis (KOA).

Multiple phenotypes characterized by different disease mechanisms have been hypothesized to explain the large variability in the knee osteoarthritis (KOA) population. The purpose of this studywas: to estimate and compare the medial and lateral knee compression forces (CF) during gait of three subgroups of KOA subjects characterized by different alignment and cartilage disruption patterns. A secondary data analysis was conducted on a sample of 39 KOA subjects and 18 controls (C). The patients were classified in the different groups according to the following criteria: Varus medial disease (VMD) (12): varus alignment and predominant medial cartilage degeneration Varus generalized disease (VGD) (17): varus alignment and cartilage degeneration that extends to the lateral compartment. Neutral alignment (NA) (10): neutral alignment. The total, medial and lateral CF corrected for body weight were estimated using an inverse dynamics model (AnyBody Modeling System, AnyBody Technology) during stance. The impulse of the medial compressive force (MCF) (overall effect of the CF over the stance) was significantly higher (P<0.01) in the VMD compared to all the other groups. Peak MCF was higher in the VMD compared to all the other groups, but the difference reached significance only when compared to the VGD group (P<0.05). The results of the regression analysis showed a significant relationship in the VMD group between alignment and impulse of the MCF (R2=0.62; P<0.01). This relationship disappears in the other groups. These findings suggest the existence of a phenotype characterized by increased MCF.

Predicting knee osteoarthritis risk in injured populations

BackgroundIndividuals who suffered a lower limb injury have an increased risk of developing knee osteoarthritis. Early diagnosis of osteoarthritis and the ability to track its progression is challenging. This study aimed to explore links between self-reported knee osteoarthritis outcome scores and biomechanical gait parameters, whether self-reported outcome scores could predict gait abnormalities characteristic of knee osteoarthritis in injured populations and, whether scores and biomechanical outcomes were related to osteoarthritis severity via Spearman's correlation coefficient. MethodsA cross-sectional study was conducted with asymptomatic participants, participants with lower-limb injury and those with medial knee osteoarthritis. Spearman rank determined relationships between knee injury and outcome scores and hip and knee kinetic/kinematic gait parameters. K-Nearest Neighbour algorithm was used to determine which of the evaluated parameters created the strongest classifier model. FindingsDifferences in outcome scores were evident between groups, with knee quality of life correlated to first and second peak external knee adduction moment (0.47, 0.55). Combining hip and knee kinetics with quality of life outcome produced the strongest classifier (1.00) with the least prediction error (0.02), enabling classification of injured subjects gait as characteristic of either asymptomatic or knee osteoarthritis subjects. When correlating outcome scores and biomechanical outcomes with osteoarthritis severity only maximum external hip and knee abduction moment (0.62, 0.62) in addition to first peak hip adduction moment (0.47) displayed significant correlations. InterpretationThe use of predictive models could enable clinicians to identify individuals at risk of knee osteoarthritis and be a cost-effective method for osteoarthritis screening.

Comparison of the trunk and pelvic kinematics during single-leg standing between individuals with knee osteoarthritis and healthy subjects

Comparison of the trunk and pelvic kinematics during single-leg standing between individuals with knee osteoarthritis and healthy subjects

Baseline Characteristics of Knee Osteoarthritis Subjects Enrolled in the ILLUSTRATE-K Study of the Anti-interleukin-1alpha/beta Dual Variable Domain Immunoglobulin ABT-981 and Factors Associated with Exclusion from the Trial

Baseline Characteristics of Knee Osteoarthritis Subjects Enrolled in the ILLUSTRATE-K Study of the Anti-interleukin-1alpha/beta Dual Variable Domain Immunoglobulin ABT-981 and Factors Associated with Exclusion from the Trial

Mitochondrial DNA haplogroups influence the risk of incident knee osteoarthritis in OAI and CHECK cohorts. A meta-analysis and functional study

ObjectiveTo evaluate the influence of the mitochondrial DNA (mtDNA) haplogroups in the risk of incident knee osteoarthritis (OA) and to explain the functional consequences of this association to identify potential...

Semi-quantitative MRI biomarkers of knee osteoarthritis progression in the FNIH biomarkers consortium cohort - Methodologic aspects and definition of change.

BackgroundTo describe the scoring methodology and MRI assessments used to evaluate the cross-sectional features observed in cases and controls, to define change over time for different MRI features, and to report the extent of changes over a 24-month period in the Foundation for National Institutes of Health Osteoarthritis Biomarkers Consortium study nested within the larger Osteoarthritis Initiative (OAI) Study.MethodsWe conducted a nested case–control study. Cases (n = 406) were knees having both radiographic and pain progression. Controls (n = 194) were knee osteoarthritis subjects who did not meet the case definition. Groups were matched for Kellgren-Lawrence grade and body mass index. MRIs were acquired using 3 T MRI systems and assessed using the semi-quantitative MOAKS system. MRIs were read at baseline and 24 months for cartilage damage, bone marrow lesions (BML), osteophytes, meniscal damage and extrusion, and Hoffa- and effusion-synovitis. We provide the definition and distribution of change in these biomarkers over time.ResultsSeventy-three percent of the cases had subregions with BML worsening (vs. 66 % in controls) (p = 0.102). Little change in osteophytes was seen over 24 months. Twenty-eight percent of cases and 10 % of controls had worsening in meniscal scores in at least one subregion (p < 0.001). Seventy-three percent of cases and 53 % of controls had at least one area with worsening in cartilage surface area (p < 0.001). More cases experienced worsening in Hoffa- and effusion synovitis than controls (17 % vs. 6 % (p < 0.001); 41 % vs. 18 % (p < 0.001), respectively).ConclusionsA wide range of MRI-detected structural pathologies was present in the FNIH cohort. More severe changes, especially for BMLs, cartilage and meniscal damage, were detected primarily among the case group suggesting that early changes in multiple structural domains are associated with radiographic worsening and symptomatic progression.

Long-Term Effects of Glucosamine and Chondroitin Sulfate on the Progression of Structural Changes in Knee Osteoarthritis: Six-Year Followup Data From the Osteoarthritis Initiative.

To examine the long-term (6-year) effect of combined glucosamine (Glu) and chondroitin sulfate (CS) treatment on cartilage volume in knee osteoarthritis (OA). Participants were from the Osteoarthritis Initiative progression and incidence subcohorts, had magnetic resonance imaging (MRI) of the target knee at baseline and 6 years, joint space width >1 mm, and data available on Glu/CS consumption (n = 1,593). They were stratified into 2 main groups based on whether or not they had medial meniscal extrusion at baseline. The group with meniscal extrusion (n = 429) was further stratified into subgroups based on exposure or no exposure to Glu/CS as follows: not exposed, 1 year, 2-3 years, and 4-6 years. Cartilage volume was assessed using fully automated quantitative MRI technology. The Jonckheere-Terpstra trend test indicated that treatment with Glu/CS significantly reduced the cartilage volume loss in the global knee, associated with the lateral compartment. Multivariate analysis further demonstrated that the extent of the treatment's positive effect was related to exposure time to treatment, the protective effect at 6 years being significant in participants exposed to ≥2 years of treatment. These findings provide future support for the long-term protective structure-modifying effects of Glu/CS treatment in knee OA subjects.

Relationship between co-contraction ratio and knee adduction moment in knee osteoarthritis subjects

Relationship between co-contraction ratio and knee adduction moment in knee osteoarthritis subjects

Comparison of body weight distribution in patients with knee osteoarthritis versus healthy subjects during sit-to-stand (STS)

Comparison of body weight distribution in patients with knee osteoarthritis versus healthy subjects during sit-to-stand (STS)

Relationships between the center of pressure and the movements of the ankle and knee joints during the stance phase in patients with severe medial knee osteoarthritis

BackgroundThe knee joint movement during the stance phase is affected by altered ankle movement and the center of pressure (COP). However the relationships between changes in the center of pressure (COP) and the altered kinematics and kinetics of the ankle and knee joints in patients with osteoarthritis (OA) of the knee are not well understood. The purpose of this study was to determine the relationships between changes in the COP and the altered kinematic and kinetic variables in ankle and knee joints during the stance phase in patients with medial knee OA. MethodsFourteen patients with knee OA (21 knees) and healthy subjects were assessed by gait analysis using an eight-camera motion analysis system to record forward and lateral shifts in the COP and the angle and net internal moments of the knee and ankle joint. Spearman rank-correlation coefficients were used to determine the relationship between these results. ResultsIn knees with medial OA, lateral shifts in the COP were correlated with knee flexion angle. Lateral shifts in the COP were correlated with the second peak of the knee extensor moment and correlated with the knee abductor moment. ConclusionsIn patients with medial knee OA, lateral shifts in the COP were negatively correlated with the kinematic and kinetic variables in the sagittal plane of the knee joints. Controlling such lateral shifts in the COP may thus be an effective intervention for mechanical loads on the knee during the stance phase in patients with knee OA.

Does knee replacement surgery for osteoarthritis improve survival? The jury is still out

BackgroundThe relation of knee replacement (KR) surgery to all-cause mortality has not been well established owing to potential biases in previous studies. Thus, we aimed to examine the relation of...

"Managing" the Placebo Effect: The Single-Blind Placebo Lead-in Response in Two Pain Models.

"Placebo effects" in analgesic medication trials for chronic pain are pervasive; however, little is known regarding mechanisms or factors that may influence the presence or magnitude of these effects. Our objective is to consider elements of the placebo response in the context of two pain models using a "single-blind placebo lead-in" design (SBPLI). As part of two pilot drug trials using knee osteoarthritis (KOA) and non-radicular low back pain (LBP) subjects, SBPLI protocols were conducted. We examined whether gender and/or diagnosis affected placebo responses as observed in changes in patient self-reported pain, depressive and pain anxiety symptoms. We also evaluated the placebo response on performance-based tests (stair climbing, range of motion (ROM), sit to stand repetitions, and 6-minute treadmill distance). VAS Pain Intensity (Now) values decreased significantly during the SBPLI for the sample as a whole, but the effects appeared stronger among LBP subjects. CES-D short form values (depressive symptoms) did not decrease significantly during the SBPLI for the sample as a whole, but some placebo effects appeared to emerge for women in the KOA group. PASS values (pain anxiety symptoms) decreased significantly, albeit mildly, during the SBPLI for the sample as a whole.Stair Climb (time) revealed no significant SBPLI effects. Bend Forward to Floor (ROM) increased significantly at the end of the SBPLI period for the sample as a whole, but the effects appeared stronger among KOA subjects. Sit to Stand Repetitions increased during the SBPLI for the sample as a whole. Treadmill Distance did not change significantly from Visit 1 to Visit 2; however, a significant Sex difference for the KOA group was found such that women showed greater Treadmill Distance at Visit 2. Placebo effects emerged across psychometric and performance-based measures, indicating the pervasiveness of this phenomenon. In this design, diagnostic and (to a lesser extent) gender categories differentials were observed during the placebo period. The SBPLI design may prove not only a robust method in studying the placebo phenomena, but also as a design element to mitigate some aspects of the placebo response in clinical trials.

Efficacy and tolerability of an undenatured type II collagen supplement in modulating knee osteoarthritis symptoms: a multicenter randomized, double-blind, placebo-controlled study

BackgroundUndenatured type II collagen (UC-II) is a nutritional supplement derived from chicken sternum cartilage. The purpose of this study was to evaluate the efficacy and tolerability of UC-II for knee osteoarthritis (OA) pain and associated symptoms compared to placebo and to glucosamine hydrochloride plus chondroitin sulfate (GC).MethodsOne hundred ninety one volunteers were randomized into three groups receiving a daily dose of UC-II (40 mg), GC (1500 mg G & 1200 mg C), or placebo for a 180-day period. The primary endpoint was the change in total Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) from baseline through day 180 for the UC-II group versus placebo and GC. Secondary endpoints included the Lequesne Functional Index (LFI), the Visual Analog Scale (VAS) for pain and the WOMAC subscales. Modified intent-to-treat analysis were performed for all endpoints using analysis of covariance and mixed model repeated measures, while incremental area under the curve was calculated by the intent-to-treat method.ResultsAt day 180, the UC-II group demonstrated a significant reduction in overall WOMAC score compared to placebo (p = 0.002) and GC (p = 0.04). Supplementation with UC-II also resulted in significant changes for all three WOMAC subscales: pain (p = 0.0003 vs. placebo; p = 0.016 vs. GC); stiffness (p = 0.004 vs. placebo; p = 0.044 vs. GC); physical function (p = 0.007 vs. placebo). Safety outcomes did not differ among the groups.ConclusionUC-II improved knee joint symptoms in knee OA subjects and was well-tolerated. Additional studies that elucidate the mechanism for this supplement’s actions are warranted.Trial registration CTRI/2013/05/003663; CTRI/2013/02/003348.

Interleukin-6 and tumor necrosis factor alpha in synovial fluid are associated with progression of radiographic knee osteoarthritis in subjects with previous meniscectomy

To explore potential associations between proinflammatory cytokines in synovial fluid and progression of osteoarthritis (OA) in meniscectomized subjects. We studied 132 subjects on average 18 years after meniscectomy, with a second examination 4-10 years later. We measured concentrations of interleukin (IL)-6, -8 and tumor necrosis factor (TNF)-α by multiplex immunoassay, graded radiographic features of tibiofemoral and patellofemoral OA according to the Osteoarthritis Research Society International (OARSI) atlas, scored patient-reported outcomes using the Knee Injury and Osteoarthritis Outcome Score (KOOS), and used logistic regression (adjusted for age, gender, body mass index, and time between examinations) for assessment of associations. Higher first examination concentrations of IL-6 and TNF-α were associated with increased risk for subsequent osteophyte progression (odds ratios (OR); 95% confidence intervals 1.05; 1.00-1.09 and 1.35; 1.03-1.75). Higher second examination concentrations of TNF-α were associated with having progressed in loss of joint space (OR 1.70; 1.15-2.52) or having worsened in the activity of daily living subscale of KOOS (OR 1.50; 1.07-2.09) in the preceding years. Subjects with increasing concentrations of IL-6 or TNF-α between examinations were five times more likely to have progressed in joint space narrowing between the same examinations, as compared to those with stable or decreasing concentrations (OR 5.17; 1.54-17.32 and 5.01; 1.32-18.92). In subjects with previous meniscectomy, higher or over time increasing synovial fluid levels of IL-6 and TNF-α seems to be associated with increased risk for progression of radiographic OA.

Accelerometer-based Physical Activity Monitoring in Patients with Knee Osteoarthritis: Objective and Ambulatory Assessment of Actual Physical Activity During Daily Life Circumstances.

Background: It is important to assess physical activity objectively during daily life circumstances, to understand the association between physical activity and diseases and to determine the effectiveness of interventions. Accelerometer-based physical activity monitoring seems a promising method and could potentially capture all four FITT (i.e. Frequency, Intensity, Time, Type) components of physical activity considered by the World Health Organization (WHO).Aim: To assess the four FITT components of physical activity with an accelerometer during daily life circumstances and compare with self-reported levels of physical activity in patients with knee osteoarthritis (OA) and a healthy control group.Methods: Patients (n=30) with end-stage knee OA and age-matched healthy subjects (n=30) were measured. An ambulant tri-axial accelerometer was placed onto the lateral side of the upper leg. Physical activity was measured during four consecutive days. Using algorithm-based peak detection methods in Matlab, parameters covering the four FITT components were assessed. Self-reported physical activity was assessed using the Short questionnaire to assess health enhancing physical activity (SQUASH).Results: Knee OA patients demonstrated fewer walking bouts (154 ±79 versus 215 ±65 resp.; p=0.002), step counts (4402 ±2960 steps/day versus 6943 ±2581 steps/day; p=0.001) and sit-to-stand (STS) transfers (37 ±14 versus 44 ±12; p=0.031) compared to controls. Knee OA patients demonstrated more time sitting (65 ±15% versus 57 ±10% resp.; p=0.029), less time walking (8 ±4% versus 11 ±4% resp.; p=0.014) and lower walking cadence (87 ±11steps/min versus 99 ± 8steps/min resp.; p<0.001). Accelerometer-based parameters of physical activity were moderately-strong (Pearsons’s r= 0.28-0.49) correlated to self-reported SQUASH scores.Conclusion: A single ambulant accelerometer-based physical activity monitor feasibly captures the four FITT components of physical activity and provides more insight into the actual physical activity behavior and limitations of knee OA patients in their daily life.

Assessment of comorbidities in patients with Symptomatic Knee osteoarthritis in Spain: the emartro study

August 2015 e113 Assessment of comorbidities in PAtients with symPtomAtic Knee osteoArthritis in sPAin: the emArtro study S. Gimenez Basallote; J. Vergara Martin; J.L. Llisterri Caro; G. Rodriguez Roca; J. Monfort Faure; F.J. de Abajo Iglesias; J. Rios Guillermo; L. Sanchez Bellmunt; M. Herrero Barbero; and J. Verges Milano Centro de Salud Limonar, Malaga, Spain; Centro de Salud Huercal de Almeria, Almeria, Spain; Centro de Salud Ingeniero Joaquin Benlloch, Valencia, Spain; Centro de Salud de la Puebla de Montalban, Toledo, Spain; Hospital del Mar, Barcelona, Spain; Hospital Universitario Principe de Asturias, Madrid, Spain; IDIBAPS, Hospital Clinic Barcelona, Barcelona, Spain; and Bioiberica, S.A., Barcelona, Spain Introduction: The primary outcome of the study is to assess the prevalence of comorbidities in symptomatic knee osteoarthritis (KOA) patients. Additionally, potential differentiating factors between KOA and non-osteoarthritic subjects will be assessed to detect a possible prognosis effect complementary to osteoarthritis. Here we present the protocol of the study that is being conducted at the moment. Material and Methods: It’s an observational, epidemiologic, multicenter, transversal study comparing comorbidities between subjects with and without KOA. The recruitment will be carried out by 65 investigators from different Spanish’s healthcare centers. 1150 subjects will be enrolled distributed in two groups: 575 KOA subjects selected and 575 sex and age-matched control subjects, without neither knee pain nor osteoarthritis. The results will be analyzed using descriptive statistics. Results: This study will provide new information about comorbidities in osteoarthritis which has become the leading cause of disability in the elderly and permanent disability caused by a rheumatic disease (RD) and one of the most frequent reasons for consultation. In other studies, it has been observed that the prevalence of comorbidities was significantly higher in osteoarthritis patients than controls (P < 0.0001) being hypertension, diabetes mellitus, chronic obstructive pulmonary disease, stroke and myocardial infarction the most prevalent osteoarthritis comorbidities. The ongoing study is in the follow-up period. Conclusions: Osteoarthritis is the most common RD, affecting 28% of those over 60 years, enduring pain, functional disability, decreased quality of life and causing significant social and economic burden. However, an important proportion of the economical costs of osteoarthritis compared to non-osteoarthritic population is due to an excessive use of sanitary resources which includes not only pharmacological treatment but also image and laboratory tests, management of treatment adverse reactions or rehabilitation and surgical interventions. The knowledge of comorbidities and concomitant medications in KOA patients will provide useful information to manage the disease more effectively and reduce its social and economic burden.

Elucidation of Dietary Risk Factors in Osteoarthritis Knee—A Case-Control Study

Background and Objective: Nutritional imbalance, combined with endocrine abnormalities, may be involved in the pathogenesis of osteoarthritis (OA). This study was conducted to determine the association of OA with dietary factors, such as quantity and quality of nutrient intake.Methods: This case-control study enrolled 180 knee osteoarthritis (KOA) subjects who met the American College of Rheumatology definition of KOA, with an equal number of matched controls. Outcome measures, such as dietary nutrient intake and its frequency, were recorded using a food frequency questionnaire.Results: Compared to controls, cases were older individuals with a higher body mass index (BMI). Physical activity scores were lower in female cases compared to male cases and controls. A significantly higher intake of phosphorus and fat was observed in overall cases (fat in females only). A significantly lower intake of vitamin C and vitamin D was observed in overall cases and the significance of vitamin D persisted on gender-wise bifurcation. On multiple logistic regression analysis, the intake of vitamin D (odds ratio [OR] = 0.79) and vitamin C (OR = 0.97) was inversely associated with the presence of KOA in the observation group, especially in females. Generally, the intake of food servings/day, green leafy vegetables (GLVs), and fats/oils was higher, whereas the intake of fruits, milk/milk products, and meat/poultry was lower in cases compared to controls.Conclusion: Low intake of vitamin D and vitamin C is a possible risk factor for KOA. Certain food groups, such as fruits, milk/milk products, and meat/poultry are beneficial for KOA. Further studies are needed to elucidate the associations between diet and KOA.

The complexity of human walking: a knee osteoarthritis study.

This study proposes a framework for deconstructing complex walking patterns to create a simple principal component space before checking whether the projection to this space is suitable for identifying changes from the normality. We focus on knee osteoarthritis, the most common knee joint disease and the second leading cause of disability. Knee osteoarthritis affects over 250 million people worldwide. The motivation for projecting the highly dimensional movements to a lower dimensional and simpler space is our belief that motor behaviour can be understood by identifying a simplicity via projection to a low principal component space, which may reflect upon the underlying mechanism. To study this, we recruited 180 subjects, 47 of which reported that they had knee osteoarthritis. They were asked to walk several times along a walkway equipped with two force plates that capture their ground reaction forces along 3 axes, namely vertical, anterior-posterior, and medio-lateral, at 1000 Hz. Data when the subject does not clearly strike the force plate were excluded, leaving 1–3 gait cycles per subject. To examine the complexity of human walking, we applied dimensionality reduction via Probabilistic Principal Component Analysis. The first principal component explains 34% of the variance in the data, whereas over 80% of the variance is explained by 8 principal components or more. This proves the complexity of the underlying structure of the ground reaction forces. To examine if our musculoskeletal system generates movements that are distinguishable between normal and pathological subjects in a low dimensional principal component space, we applied a Bayes classifier. For the tested cross-validated, subject-independent experimental protocol, the classification accuracy equals 82.62%. Also, a novel complexity measure is proposed, which can be used as an objective index to facilitate clinical decision making. This measure proves that knee osteoarthritis subjects exhibit more variability in the two-dimensional principal component space.

Serum cytokines are increased and circulating micronutrients are not altered in subjects with early compared to advanced knee osteoarthritis

Knee osteoarthritis (OA) is a leading cause of physical disability. At the early stage of knee OA, the increase in synovial fluid cytokine concentrations could contribute to the pathogenesis of OA by degrading articular cartilage. It is unknown, however, if inflammatory cytokines increase systemically at the early or advanced stage of knee OA. The systemic increase of inflammatory cytokines could be detrimental to the endogenous status of micronutrients that protect against excessive inflammation and cytokine-mediated events. The purpose of this study was to test the hypothesis that an increase in serum cytokines associate with a decrease in circulating micronutrients in subjects with early compared to advanced knee OA. Advanced knee OA subjects (n=14) displayed radiographic, pain, and muscular weakness symptoms of knee OA. Early knee OA subjects (n=14) were matched (age, gender, and body mass index) to the advanced OA group and displayed one or two of the aforementioned symptoms of knee OA. Inflammatory cytokines, vitamins C (ascorbic acid), D (25-hydroxyvitamin D), and E (α- and γ-tocopherols), and β-carotene were measured in fasting blood samples. In the early OA group, serum tumor necrosis factor (TNF)-α, interleukin (IL)-5, IL-6, IL-12, and IL-13 concentrations were significantly (all p<0.05) increased. Circulating ascorbic acid, 25-hydroxyvitamin D, α- and γ-tocopherol’s, and β-carotene concentrations were not significantly different between groups. Based on these preliminary results, we conclude that the systemic increase of inflammatory cytokines is not associated with a decrease in circulating micronutrients in subjects with early compared to advanced knee OA.

Energy recovery in individuals with knee osteoarthritis

Pathological gaits have been shown to limit transfer between potential (PE) and kinetic (KE) energy during walking, which can increase locomotor costs. The purpose of this study was to examine whether energy exchange would be limited in people with knee osteoarthritis (OA). Ground reaction forces during walking were collected from 93 subjects with symptomatic knee OA (self-selected and fast speeds) and 13 healthy controls (self-selected speed) and used to calculate their center of mass (COM) movements, PE and KE relationships, and energy recovery during a stride. Correlations and linear regressions examined the impact of energy fluctuation phase and amplitude, walking velocity, body mass, self-reported pain, and radiographic severity on recovery. Paired t-tests were run to compare energy recovery between cohorts. Symptomatic knee OA subjects displayed lower energetic recovery during self-selected walking speeds than healthy controls (P=0.0018). PE and KE phase relationships explained the majority (66%) of variance in recovery. Recovery had a complex relationship with velocity and its change across speeds was significantly influenced by the self-selected walking speed of each subject. Neither radiographic OA scores nor subject self-reported measures demonstrated any relationship with energy recovery. Knee OA reduces effective exchange of PE and KE, potentially increasing the muscular work required to control movements of the COM. Gait retraining may return subjects to more normal patterns of energy exchange and allow them to reduce fatigue.