The association of external knee adduction moment with biomechanical variables in osteoarthritis: A systematic review

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The association of external knee adduction moment with biomechanical variables in osteoarthritis: A systematic review
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  Review The association of external knee adduction moment with biomechanical variables inosteoarthritis: A systematic review Nasim Foroughi ⁎ , Richard Smith, Benedicte Vanwanseele Discipline of Exercise, Health and Performance, Faculty of Health Sciences, University of Sydney, Sydney, NSW, Australia a b s t r a c ta r t i c l e i n f o  Article history: Received 21 July 2008Received in revised form 9 December 2008Accepted 13 December 2008 Keywords: OsteoarthritisGaitKnee adduction moment Context:  Osteoarthritis (OA) is a musculoskeletal disorder primarily affecting the older population andresulting in chronic pain and disability. Biomechanical variables, associated with OA severity such as externalknee adduction moment (KAM) and joint malalignment, mayaffect the disease process byaltering the bone-on-bone forces during gait. Objective:  To investigate the association between biomechanical variables and KAM in knee OA. Method:  A systematic search for published studies' titles and abstracts was performed on Ovid Medline ® ,Cumulative index to Nursing and Allied Health, PREMEDLINE, EBM reviews and SPORTDiscus. Fourteenstudies met the inclusion criteria and were considered for the review. Results:  The magnitude and time course of KAM during gait appeared to be consistent across laboratories andcomputational methods. Only two of the included studies that compared patients with OA to a control groupreported a higher peak KAM for the OA group. Knee adduction moment increased with OA severity and wasdirectly proportional to varus malalignment. Classifying the patients on the basis of disease severitydecreased the group variability, permitting the differences to be more detectable. Conclusions:  Biomechanical variables such as varus malalignment are associated with KAM and thereforemay affect the disease process. These variables should be taken into considerations when developingtherapeutic interventions for individuals suffering from knee OA.Crown Copyright © 2008 Published by Elsevier B.V. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3042. Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3042.1. Literature search. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3042.2. Inclusion/exclusion criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3042.3. Data extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3043. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3043.1. Study selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3043.2. Quality assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.3. Biomechanical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.3.1. Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.3.2. Measurement methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.4. Patient selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.4.1. Disease severity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.4.2. Age and body weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.4.3. Impairments of lower limb joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.5. Gait affecting variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.5.1. Medication washout period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.5.2. Footwear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.5.3. Arm immobilization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3053.5.4. Radiographic assessment of knee alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 The Knee 16 (2009) 303 – 309 ⁎  Correspondingauthor.DisciplineofExercise,HealthandPerformance,FacultyofHealthScience,UniversityofSydney,POBox170,LidcombeNSW1825Australia.Fax:+61293519204. E-mail address:  nfor3501@mail.usyd.edu.au (N. Foroughi).0968-0160/$  –  see front matter. Crown Copyright © 2008 Published by Elsevier B.V. All rights reserved.doi:10.1016/j.knee.2008.12.007 Contents lists available at ScienceDirect The Knee  3.6. Cohorts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3063.6.1. Cross-sectional studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3063.6.2. Prospective observational studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3073.7. Does a relationship exist between KAM and OA related aspects? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3083.7.1. Disease severity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3083.7.2. OA symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3083.7.3. OA progression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3083.7.4. Joint alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3083.7.5. Laxity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3084. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3085. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3096. Con fl ict of interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 1. Introduction Osteoarthritis (OA), the most common type of arthritis, is adegenerative joint disease which causes chronic pain, stiffness anddisability in all ages, particularly in older people in the developedworld [1]. Age, joint injury, obesityand malalignment are some of thewell-known risk factors for OA [2 – 5]. Incidence and progression ratesof OA are 2.5% and 3.6% per year, respectively [6]. Women are at ahigherrisk(4.9%)thanmen(2.6%)andtheprevalenceofOAincreaseswith age [7].Osteoarthritis is chronic degeneration of articular cartilage andloading of the knee joint is crucial for the maintenance of cartilage.About60 – 80%ofthecompressiveloadatthemedialtibiofemoralkneecompartment is distributed by the external knee adduction moment(KAM) measured by internal knee abduction moment [8]. The KAM ismainlydeterminedbythegroundreactionforceanditsleverarm.Thelineofactionofthegroundreactionforceisdirectedtothemedialsideand the centre of the knee during walking and its lever arm is theperpendicular distance from this force vector to the knee joint centre.The KAM tends to adduct the knee into a varus position and issigni fi cantly correlated with disease severity [9].Patients with OA tend to modify spatial and temporal parametersand muscle moments during walking to reduce the pain and knee joint moments [10,11]. For example, several studies found thatpatients with OA walk more slowly, walk with a reduced knee  fl exionangle at heel strike, and reduced total knee range of motion [11 – 15].Biomechanical variables, more speci fi cally KAM, have recentlybeen of interest as important factors in the development andprogression of OA. Medial compartment loads in knee OA arecharacterized by KAM [14] and other biomechanical variables maycontribute in altering those loads on the joint. This emphasizes theimportance of investigating the cause and effect link between KAMand other biomechanical variables to develop a better understandingof the disease process and to develop therapeutic interventions. Wehypothesized that biomechanical variables such as varus malalign-mentanddiseaseseverityarecloselyassociatedwithKAMinkneeOA.The purpose of this study was to investigate the association betweenthe biomechanical variables and KAM in knee OA. 2. Materials and methods  2.1. Literature search Database searches were undertaken by one reviewer in December2006onOvidMedline ® (MEDL)(1950 – 2006,December),EBMReviews(All  —  Cochrane DSR, ACP Journal Club, DARE, and CCTR) (1991 – 2006,December), PREMEDLINE (Most Recently Published) Cumulative indexto Nursing and Allied Health (CINHAL, 1982 – 2006, December), andSPORTDiscus (1830 – 2006, December). The following keywords weregroupedandsearchedinall fi eldswithconjunction “ or ” ineachgrouptoensure that all relevant articles were obtained. Group one consisted of keywords:  “ walking ” ,  “ walking velocity ” ,  “ walking speed ” ,  “ gait ” ,  “ gaitvelocity ” ,  “ gait speed ” . Keywords  “ knee ” ,  “ knee adduction moment ” , “ adduction moment ”  and,  “ adductor moment ”  built up the secondgroup. Group three included  “ osteoarthritis ” ,  “ arthritis ” ,  “ arthritic ” , andgroup four included  “ obesity ” ,  “ laxity ” ,  “ knee alignment ” ,  “ musclestrength ” , and  “ OA progression ” . In the second stage, the searchedresultsofeachgroupwerecombinedwithconjunction “ and ” inall fi elds.All searches were carried out on English language titles, abstracts andfull-length articles. To extract additional papers, reference lists of allincluded articles were searched.  2.2. Inclusion/exclusion criteria In order to prevent selection bias, inclusion and exclusion criteriawere decided on prior to the review; and these were applied once allarticles were retrieved (Table 1).  2.3. Data extraction The database searches were carried out by one reviewer. The datawere extracted by two reviewers and all the relevant articles werediscussed between them. All the authors reviewed the extracted data.The quality assessment was based on the data collection methods,study design and sample characteristics of the reviewed studies. 3. Results  3.1. Study selection According to the agreed inclusion/exclusion criteria, a total of 50 potentiallyrelevant studies were identi fi ed for this review. The results of the article selectionprocessarereportedinFig.1.Fourteenstudieswereincludedinthisreview.Fivestudies were designed to compare the gait characteristics of patients with OA across groupswith different disease severity or with a control group [12,13,15 – 17]. Three studiescompared the gait kinematics and kinetics of patients with OA to a control group[12,13,16] andonestudyinvestigatedtherelationshipbetweenKAMandwalkingspeedin both OA and a control group [17]. These results are presented in Tables 2 and 3. Nine studies reported changes in gait patterns over time without intervention orinvestigated correlation between KAM and other biomechanical factors in patients withknee OA [9,11,18 – 24]. One studycomparedthe KAM inOA patients withorwithout varusthrust (the lateral knee displacement) [18]. One study examined the disease progression  Table 1 Inclusion and exclusion criteria of the review. Inclusion Study design: cross-sectional or prospective observationalStudy population: patients with knee osteoarthritisOutcome measures:OA assessed using either clinical and/or radiological criteria.KAM measured using 3D gait analysis system. Exclusion Interventional studies (offering physiotherapy, exercise participation, nutritionaltherapy, medication therapy or operation)304  N. Foroughi et al. / The Knee 16 (2009) 303 –  309  predictability ofKAM at baseline [21]. Five prospectiveobservational studies investigatedthe relationship between KAM and alignment [11], radiographic measure of diseaseseverity [9,11,19,24] clinical assessment of pain, stiffness or function [11] and laxity [20]. Tables 4 and 5 summarize the characteristics of these studies.  3.2. Quality assessment  The following factors were considered in orderto assess the quality of the includedstudies: biomechanical methods (model, measurement methods), patient selection(disease severity, age and body weight, impairments of lower limb joints), and gaitaffecting variables (medication washout period, footwear, arm immobilization, radio-graphic assessment of knee alignment). None of the articles were excluded from thereview based on poor study quality.  3.3. Biomechanical methods 3.3.1. Model Most of the studies are limited to  fi ve degree of freedom by using only two markerspersegmentincludingsuperioriliacspine,greatertrochanter,lateraljointlineoftheknee,lateral malleolus, lateral aspect of the calcaneus, and head of the  fi fth metatarsal [9,11 – 13,15 – 19,21,23,24].ThesinglelateralmodelsystemwouldexaggerateKAMrelativetoasixdegreeoffreedom3-dimensionalsystem.Thein fl uenceofshankmovementintransverseplane on KAM and the joint's axial rotation would also be neglected. We acknowledge,however, that some studies included in their method the assumption that no axialrotation occurred about the long axis of the joint [11]. The employment of three markers per segment has been recommended previously and is important especially whenpatients with laxity or lateral thrust are studied [25,26].  3.3.2. Measurement methods Thetest – retestreliabilityandstandardmethodofmeasuringpeakKAMwasreportedpreviously[26].AlargevariationinmeasuringanddescribingKAMwasobservedintermsof units; in expressing KAM (internally or externally); in the magnitude of KAM(maximum, mean,  fi rst or second peak KAM); and the phase of the gait cycle and theposition of the patient (during ambulation or single stance KAM) in which KAM wasmeasured. Three studies reported KAM in Nm/kg [13,16,19] and one study in Nmm/kgm[20] rather than normalizing it to percentage body weight per height [12,15,17,27]. As illustratedinFig.2,KAMhastime-varyingcharacteristicsandtwopeaks;onein30%ofthestancephaseandtheotherinterminalstance.Twostudiesreportedthe fi rstorthesecondpeakKAM[15,17],whileothersreportedthemeanKAM[9]orpeakKAMduringtheentire stance phase [12,13,16]. One study has introduced the knee adduction angular impulse,which is the magnitude of KAM over time [23]. KAM has been measured and reported indifferent phases of the gait cycle in various studies [22,27].  3.4. Patient selection 3.4.1. Disease severity Disease severity varied amongst the patients in selected studies. The patients wereclassi fi ed as being asymptomatic, having mild, moderate, and severe OA in most of theincluded studies ( n =12) based on theK/L grade[28].Onlythreestudies haveused theWOMAC score to classify the patients into less severe and more severe groups [15,17].One study used X-ray images and clinical examination for inclusion of the participants[12], however, the results of this study were not different from the reported results inthe literature. The remaining studies ( n =2) did not report the disease severity or thetool employed to measure it [13,20]. Only one of the included studies has radiographic evidence of OA for control/asymptomatic subjects and the remaining studies haveonlyclinically assessed the subjects [20].  3.4.2. Age and body weight  Age and body weight can affect the joint moment during gait [29,30]. In one study,agewassigni fi cantlydifferentbetweenpatients withOAandthecontrolgroup[12]andthe subjects' BMI was not reported in two of the studies [19,20].  3.4.3. Impairments of lower limb joints Only some of the studies have excluded patients from their studies if they hadmusculoskeletal disorders in other joints [12,21,24], OA in spine or hip [19] and OA grade higher than moderate in ankle or hip [15,17]. In the remaining studies,undiagnosed disorders in other joints could have resulted in misclassi fi cation biaswhich would have attenuated any differences.  3.5. Gait affecting variables 3.5.1. Medication washout period InthreestudiespatientswithOAundertooktheassessmentsafterafour-weekwashoutperiod from their medication and/or physiotherapy [9,21,24], although the remaining studiesdidnotreportanywashoutperiod.Theusualloadingpatternmaynotbeobservedinthe presence of medication. Lack of medication washout would exaggerate the differencebetween patients with OA relative to controls. Thus, the true magnitude of differencebetweenpatientswithOAandcontrolsmaybemuchgreaterthanreportedintheliterature.  3.5.2. Footwear  Footwear may detrimentally increase the loads on lower extremity joints [31]. Inone study subjects were asked to wear athletic shoes to perform the gait [16]. In twostudies subjects wore their own comfortable shoes [15,17]. There is no report of thefootwear condition in the remaining studies.  3.5.3. Arm immobilization Subjects performed the walking trials with both arms folded in front of their chestin two studies [21,24] which may have changed the normal pattern of gait.  3.5.4. Radiographic assessment of knee alignment  The angle between shank and thigh longitudinal mechanical axes describes thealignment of the lower extremity and is de fi ned as the angle in the frontal planebetween the line connecting the center of the femoral head, the centre of the tibialplateau,thelineconnectingthecentreof thetibialplateauandthecentreof theankle joint [24]. Patient position signi fi cantly affects radiographic measure of frontal plane Fig.1.  Characteristics of the studies included in the review.305 N. Foroughi et al. / The Knee 16 (2009) 303 –  309  knee alignment [22]. Patient position during radiographic assessment was not reported in two studies [12,13]. Mechanical angle was measured using radiographs taken from patients of different weight bearing status [20,22]. It is important to applyand/or report a standard method during radiographic assessment to provide aconsistent way of evaluating the patients over time and to compare the reportedresults in the literature.  3.6. Cohorts 3.6.1. Cross-sectional studies Four studies included women and men [12,15 – 17] and one study included womenonly [13]. A total number of 248 patients with OA (age: 65±7 yrs) and 129 controls (age: 57±19 yrs) participated in these  fi ve studies. The symptomatic group of these  Table 2 Baseline characteristics of the studies comparing KAM within OA group or with a control group.Author, year, country Sample size, %femaleAge (years), BMI (kg/m 2 ) OA diagnosis tools, severity(# or % sample)Mechanical axis °, radiographic positionOA Controls OA Controls OA OAGok, H., 2002, Norway 13,%100 13, %100 (46 – 60) ⁎ , 31.2 NR, 29.2 NR, early medial OA, (NR) NR Kaufman, K. R., 2001, USA 139,%66 20, % 55 57±12.5, 30.5 30±9, 25.1 Clinical examination and X-rays,NR NR Messier, S. P., 2005, USA 10, % 90 10, % 90 74.1±1.49,  b 27 73.0±1.61,  b 27 Clinical examination and X-rays NR K/L grades:1 ( n =3)2 ( n =5)3 ( n =2)Mundermann, A., 2004,USA44, % 54 44, % 54 65.4±10,27.4±4.7 63.3±107, 26.6±3.3WOMAC and X-rays MS: 6.0±4.5°, vs.K/L grades: LS: 0.0±2.9° ( P  b 0.001)0 ( n =4) Full length, weight bearing1 ( n =4)2 ( n =48)3 ( n =19)4 ( n =13)Mundermann, A., 2005,USA42, % 30 42, % 30 65.2±12.5, 61.7±12.3, WOMAC and X-rays NR, full length, weight bearingLS( ≤ 2): 26.9±3.1 LS( ≤ 2): 26.1±2.6 K/L grades:MS( ≥ 3):27.8±4.8 MS( ≥ 3):27.1±4.0  ≤ 2 ( n =19) ≥ 3 ( n =23)Kim, W.Y., 2004, UK 13, NR 14, NR 60 (47 – 72) ⁎ , NR 54.6 (39 – 73) ⁎ ,NR K/L grades: Weight bearing, anterior/posterior, lateral, skyline, NR 2 ( n =5)3 ( n =7)4 ( n =2)Sharma, L.,1998, USA 54, % 42 NA 62.4±10.1, 29 NA K/L grades: NR, weight bearing, anterior/posterior, full kneeextension0 ( n =2)1 ( n =13)2 ( n =21)3 ( n =13)4 ( n =5)Notes: Values are mean ± Standard Deviation, except where indicated otherwise ( ⁎ ); OA, Osteoarthritis; SD, Standard Deviation; vs., versus; MS, More Severe; LS, Less Severe; K/L grades, Kellgren and Lawrence grades; BMI, Body Mass Index; NR, Not Reported; °, degrees.  Table 3 Reported results of the studies comparing KAM within OA group or with a control group.Author, year, country Independent variable (KAM) Walking velocity (m/s)OA Controls P, unit OA Controls PGok, H., 2002, Norway  P  =0.5 0.9±0.1 1.0±0.1  P  =0.01Left leg: 0.44±0.16 0.39±0.10  P  =0.01Right leg: 0.45±0.11 0.33±0.05 Peak, Nm/kgKaufman, K. R., 2001, USA 2.23±0.82 2.60±0.76  P  =0.41 1.09±0.11 1.17±0.14  P  =0.0001Peak, % BW×HtMessier, S. P., 2005, USA 0.25±0.06 ⁎  0.33±0.06 ⁎  P  =0.30 1.09±0.036 ⁎  1.29±0.084  – 15.4  ¤ Peak, Nm/kgMundermann, A., 2004, USA 3.27±0.88 3.16±0.92  P  =0.421 1.243±0.206 1.240±0.185  P  =0.946Peak, % BW×HtMundermann, A., 2005, USA % Difference: 1st peak:MS vs. C: 11.4%  P  =0.039MS vs. LS: 27.9%  P  b 0.001 ⁎  LS: 1.26±0.23 1.16±0.15  P  =0.197NALS vs. C: − 32.8% 2nd peak MS: 1.25±0.22 1.23±0.21  P  =0.833LS vs. MS: − 37.8%  P  b 0.001 P  b 0.001 ⁎ % BW×HtKim, W.Y., 2004, UK 0.71±0.20 0.55±0.18  P  =0.012 NR NR NR Peak, Nm/kgSharma, L.,1998, USA Left knee:  P  b 0.001K/L (0 – 2): 3.0±1.1 vs.K/L (3 – 4): 5.1±0.9NA NR NR NR Right knee:K/L (0 – 2): 2.8±0.7 vs.  P  b 0.001K/L (3 – 4): 4.1±0.7 Mean, % BW×HtNotes: Values are mean±Standard Deviation, except where indicated otherwise ( ⁎ );  ⁎ , mean±Standard Error; OA, Osteoarthritis; KAM, Knee Adduction Moment; vs., versus; %BW×Ht, %Bodyweight×Height;MS,MoreSevere;LS, LessSevere;K/L grades,Kellgrenand Lawrencegrades;NR, Notreported; NA,Not Applicable; C,Controls; Nm,Newtonmeter;¤, % difference (negative: OA N C); °, degrees; m/s, meters/seconds.306  N. Foroughi et al. / The Knee 16 (2009) 303 –  309  studies had OA in at leastone knee according tothe American College of Rheumatology(ACR) criteria [32]. The participants were included if they met theK/L grade of 1 – 4 andhad at least some dif  fi culty with two or more items in the WOMAC index (Table 2).  3.6.2. Prospective observational studies Eight studies included women and men [9,11,18,20 – 24], whereas one study didnot report the participant's gender [19]. A total number of 617 patients with OA (age:  Table 4 Baseline characteristics of the prospective observational studies.Author, year,countrySample size, % female Age (years), BMI (kg/m 2 ) OA diagnosis tools,severity (# or % sample)Mechanical axis °, radiographic positionSpecogna, A.V.,2007, Canada40, % 32 44±9, 28.6±6.9 K/L grades: NR, full length, supine, single and double limbstanding1 (% 10)2 (% 25)3 (% 58)4 (% 8)Thorp, L., 2006,USALS (K/L=2): 66, % 74 LS (K/L=2): 56.7±10.7, 28.7±4.0 Clinical examinationand X-raysNR, full length  –  weight bearing, anterior/posterior,full knee extensionMS (K/L=3): 23, % 73 MS (K/L=3): 62.7±7.8, 31.2±4.0, K/L grades:(K/L=0 – 1): 28, % 64 (K/L=0 – 1): 53.3±6.8, 27.4±4.2 0 – 1 ( n =28)2 ( n =66)3 ( n =23)Chang, A., 2004,USA222, % 73 68±10.7, 30.0±6.0 WOMAC index: Varus (42%): 3.6°±2.42 ( n =114) Valgus (50%): 3.8°±2.83 ( n =92) Neutral (8%): 04 ( n =16) Full length, anterior/posteriorHurwitz, D.E.,2002, USAOA: 62, % 48 vs. Controls: 49, % 51 OA: 62±10, 46 vs. Controls: 59±10, 45 ACR II or III K/L Grades: 5±5° (range: − 9 – 15)0 – 1 (14%) Weight bearing, anterior/posterior, full kneeextension2 (39%)3 (36%)4 (11%)Wada, M., 2001, Japan69, % 85 74 (58 – 82), 27 ACR and X-rays LS: 10° (0 – 15) vs. MS: 14° (5 – 33);  P  b 0.001K/L grades: Full length  –  weight bearing, anterior/posterior, fullknee extension1 – 2 ( n =23)3 – 4 ( n =46)Miyazaki, T.,2002, JapanOA progression group: 32, % 87 vs.none-progression group: 42, % 71OA progression group: 70.5±6.2, 24 vs.none-progression group: 68.7±8.7, 24K/L 4.6°±3.8 vs. 6.3°±4.0;  P  =0.061 ( n =20) Full length  –  weight bearing, anterior/posterior,lateral, skyline, knee in semi- fl exed position2 ( n =22)3 ( n =23)4 ( n =9)Lewek, M. D.,2004, USAOA: 12, % 50 vs. controls: 12, % 50 OA: 50.3±7.4, NR vs. controls: 49.5±6.1, NR NR Weight bearing, anterior/posterior, knee  fl exedat 30°Notes: Values are mean±Standard Deviation, except where indicated otherwise ( ⁎ ); OA, Osteoarthritis; MS, More Severe; LS, Less Severe; vs., versus; K/L grades, Kellgren andLawrence grades; ACR, American College of Rheumatology; BMI, Body Mass Index; NR, Not reported; °, degrees.  Table 5 Reported results of the prospective observational studies.Author, year, country Independent variable, unit Dependent variables EffectsSpecogna, A.V., 2007, Canada Peak KAM (%BW×Ht):Single limb standing Alignment  R = − 0.46,  P  =0.003Double limb standing Alignment  R = − 0.45,  P  =0.004Supine Alignment  R = − 0.43,  P  =0.006Thorp, L., 2006, USA Peak KAM (%BW×Ht) in:Terminal stance Walking velocity  R = − 0.322,  P  b 0.01Overall stance OA grade  R =0.294,  P  b 0.01Mid-stance OA grade  R =0.304,  P  b 0.01Terminal stance OA grade  R =0.332,  P  b 0.01Chang, A., 2004, USA Peak KAM (%BW×Ht) Varus thrust OR: 1.03, 95% CI 0.64 – 1.42,  P  b 0.0001Varus thrust Physical function OR: 2.23, 95% CI 0.71 – 6.94Varus thrust OA progression OR: 3.96, 95% CI 2.11 – 7.43Hurwitz, D.E., 2002, USA 1st KAM Alignment  R =0.74,  P  b 0.0012nd KAM Alignment  R =0.75,  P  b 0.0011st KAM Pain  R = − 0.250,  P  =0.0522nd KAM (%BW×Ht) Pain  R = − 0.210,  P  =0.104Wada, M., 2001, Japan Peak KAM K/L grades (1 – 2) 3.5 (1.1 – 7.4),  P  =0.06Peak KAM (%BW×Ht) K/L grades (3 – 4) 5.3 (0.4 – 8.4),  r  =0.62,  P  b 0.001Kim, W.Y., 2004, UK Peak KAM WOMAC pain  r  =0.63,  P  =0.02Peak KAM (Nm/kg) WOMAC function  r  =0.63,  P  =0.01Miyazaki, T., 2002, Japan KAM Pain  r  = − 0.33,  P  b 0.001KAM Alignment  r  =0.23,  P  b 0.001KAM Progression OR 6.46 (2.40 – 17.45),  P  =0.0002KAM JSN loss  r  =0.62,  P  b 0.0001Sharma, L.,1998, USA Mean KAM JSW (left knee)  r  = − 0.45,  P  =0.003Mean KAM JSW (right knee)  r  = − 0.47,  P  =0.002Mean KAM JSW OR   –  0.63 ( − 0.96  –  0.29)Mean KAM K/L (left knee)  r  = − 0.68,  P  b 0.001Mean KAM (%BW×Ht) K/L (right knee)  r  = − 0.60,  P  b 0.001Lewek, M. D., 2004, USA Peak KAM (Nmm/kgm) Laxity  R 2 =0.213,  P  =0.027Notes: OA, Osteoarthritis; KAM, Knee Adduction Moment; MS, More Severe; LS, Less Severe; %BW×H, %Body weight×Height; K/L grade, Kellgren and Lawrence grade; OR and 95%Con fi denceIntervals,oddsratioand95%con fi denceintervals;JSN,jointspacenarrowing;JSW,jointspacewidth;Nm,Newtonmeter;Nmm/kgm,Newtonmillimeter/kilogrammeter.307 N. Foroughi et al. / The Knee 16 (2009) 303 –  309
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