Jul 15, 1997 - Background: The quadriceps weakness commonly associ- ated with osteoarthritis of the knee is widely believed to result from disuse atrophy ...
15 July 1997
Volume 127
Number 2
Annals of Internal Medicine Quadriceps Weakness and Osteoarthritis of the Knee Charles Slemenda, DrPH; Kenneth D. Brandt, MD; Douglas K. Heilman, MS; Steven Mazzuca, PhD; Ethan M. Braunstein. MD; Barry P. Katz, PhD; and Fredric D. Wolinsky, PhD
Background: The quadriceps weakness commonly associated with osteoarthritis of the knee is widely believed to result from disuse atrophy secondary to pain in the involved joint. However, quadriceps weakness may be an etiologic factor in the development of osteoarthritis. Objective: To explore the relation between lowerextremity weakness and osteoarthritis of the knee. Design: Cross-sectional prevalence study. Setting: Population-based, with recruitment by randomdigit dialing. Participants: 462 volunteers 65 years of age or older. Measurements: Radiographs of the knee were graded for the presence of osteoarthritis. Knee pain and function were assessed with the Western Ontario and McMaster Universities Arthritis Index, the strength of leg flexors and extensors was assessed with isokinetic dynamometry, and lower-extremity lean tissue mass was assessed with dualenergy x-ray absorptiometry. Results: Among participants with osteoarthritis, quadriceps weakness, but not hamstring weakness, was common. The ratio of extensor strength to body weight was approximately 20% lower in those with than in those without radiographic osteoarthritis. Notably, among women with tibiofemoral osteoarthritis, extensor weakness was present in the absence of knee pain and was seen in participants with normal lower-extremity lean mass (extensor strength, 30.1 Ib-ft for tbose with osteoarthritis and 34.8 !b-ft for those without osteoarthritis; P < 0.001). After adjustment for body weight, age, and sex, lesser quadriceps strength remained predictive of both radiographic and symptomatic osteoarthritis of the knee (odds ratio for prevalence of osteoarthritis per 10 Ib-ft loss of strength, 0.8 [95% Cl, 0.71 to 0.90] for radiographic osteoarthritis and 0.71 [Cl, 0.51 to 0.87] for symptomatic osteoarthritis). Conclusion: Quadriceps weakness may be present in patients who have osteoarthritis but do not have knee pain or muscle atrophy; this suggests that the weakness may be due to muscle dysfunction. The data are consistent with the possibility that quadriceps weakness is a primary risk factor for knee pain, disability, and progression of joint damage in persons with osteoarthritis of the knee. Ann Intern Med. 1997:127:97-11)4. For aurhor aUilialions and current author adcJrtJsses. see end of text.
O
steoarthritis of the knee is the most common cause of chronic disability among older persons in the United States (1). In persons whh symptomatic osteoarthritis of the knee, quadriceps muscle weakness is common and is widely believed to result from disuse atrophy secondary to joint pain. Although exercises to strengthen the quadriceps may relieve joint pain in persons with osteoarthritis of the knee (2-6), the role of periarticular muscle weakness in the pathogenesis of joint pain and disability in these persons is poorly tjnderstood. The basis for the beneficial effect of strengthening exercises is unclear, and the duration of the improvement has not been studied. Furthermore, the possibility that muscle weakness is an etiologic factor underlying the pathologic changes of osteoarthritis has seldom been considered. Elucidation of the role of muscle weakness in osteoarthritis is particularly important given our growing understanding of safe and effective methods for increasing strength in elderly persons (7, 8). A substantial proportion of persons who have radiographic evidence of osteoarthritis of the knee have no joint pain (9). Because asymptomatic persons with radiographic changes seldom seek medical attention for osteoarthritis, muscle weakness has not been studied previously in this group. Thus, it is not known whether quadriceps weakness precedes or follows joint pain or (if it follows joint pain) whether it is mediated by disuse atrophy or by physiologic mechanisms that may inhibit muscle contraction (10). To address this issue, we studied the relation among lower-extremity muscle strength, lower-extremity lean tissue mass, and osteoarthritis of the knee in men and women 65 years of age and older. Methods Study Group To obtain a sample of elderly persons living in the community, we conducted brief telephone intcr©1997 Amtirican Qillcgc nl' Physicians
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views with residents of households in central Indiana. Potential participants were selected through modified random-digit dialing to increase the sampled proportion of persons 65 years of age and older. Persons were eligible if they met the minimal criteria for participation: They were willing and able to provide informed consent and to undergo the necessary strength assessments and other evaluations. Persons were excluded if they had had amputations of both lower extremities, had undergone total knee arihroplasty, or had recently had a eerebrovaseular accident or myocardial infarction. A total of 462 persons (approximately 55'^'(. of all who were eligible) agreed to participate and completed the following evaluations. Evaluations Radiography of lhe Knee Standing anteroposterior and lateral radiographs of both knees of eaeh study participant were obtained, and the severity of osteoarlhritis in the tibiofemoral compartment was graded by a musculoskeletal radiologist according to the criteria of Kellgren and Lawrence. Similar criteria, based on the presence of osteophytes and joint space narrowing, were used for the patellofemoral compartment (11). The radiologist was blinded to the clinical status and characteristics of all patients. A participant had to have a Kellgren and Lawrence grade of 2 or more in either knee to be classified as having osteoarthritis. Knee Pain and Function The Western Ontario and McMaster Universities Arthritis Index was used to evaluate knee pain and function (12). This index assesses the severity of knee pain during 5 activities or situations (walking on a fiat surface, going up or down stairs, al nighl while in bed, sitting or lying, and standing upright) and the severity of impairment of lower-extremity function during 17 aclivilies. Pain and functional impairment were assessed in each knee separately. Responses to each question about the severity of knee pain and level of impairment were recorded on a eategorical scale as none, mild, moderate, severe, or extreme. Eaeh category was assigned a corresponding numeric score from 1 lo 5 (3 = extreme). Hence, the range on the pain scale was 5 to 25 and the range on the physical impairment scale was 17 to 85 {H5 = greatest functional limitation). For the purposes of analysis, participants wht) rated the severity of their knee pain as moderate or greater (>3) with any of the 5 activities on more ihan half of the days in the month preceding the evalualion were considered to have knee pain. Thus, pain in the more distant past thai had resolved was not included.
Participants were also questioned about eurrent and prcvi(ius regular (^5 times per week) or occasional use of over-the-counter and prescription analgesics and nonsteroidal anti-infianmiatoiT drugs (NSAIDs) in the past year. Lower-Extremity Muscle .Strength The strength of each leg was evaluated by using an isokinetic dynamometer (KIN-COM 50011. Chatleex Coi"p.. Hixson. Tennessee). Peak toi'quc was recorded in bolh the concentric (contractions during muscle shortening) and eccentric (contractions during muscle lengthening) modes. Participants were allowed several submaximal or maximal practice efforts to familiarize themselves with the operation of the dynamometer. Once formal testing began, the best of three maximal efforts was recorded for fiexion and extension at both 60 degrees per seeond and 120 degrees per second. Aborted eff'orts were repealed in order lo obtain the best possible representation of strength for each participant. Concentric and eccentric testing yielded similar results, but because of greaier variability in eccentric testing, only the concentric lest results are shown. Lower-Extremity Lean Tissue Mass Total-body dual-energy x-ray absorptiometry was done in al! partieipants by using a Lunar-DPX-L instrument (Lunar Corp.. Madison. Wisconsin). Results were analyzed for loial and regional body composition, including body fat. mineral, and lean components (lean components were components olher than fat or mineral). The right and left lower extremities were analyzed separately. The lower extremity was defined as al! tissue below a diagonal line drawn outward and upward from the groin area through the femoral neek. Statistical Analysis Partieipants were divided into four groups on the basis of presence or absence of radiographic evidence of osteoarthritis of the knee and presence or absence of knee pain, as defined above. Men and women were compared by using the /-test. Comparisons of Arthritis Index pain and functional impairment scores were done by using nonparametric approaehes. For analyses of continuous data involving more than two groups of participants (for example, osteoarthrilis with or without knee pain), analysis of variance was used to determine whether an overall difference was present. The Fisher protected leastsignificant-diffcrence procedure was used for pairwise comparisons. Comparisons within participants (for example, comparison of the two legs in a person with unilateral osteoarlhrilis of the knee) were done by using paired ?-tests. Regression models were constructed with ihc licncralized eslimatine
15 Julv 1997 • Annals of tnternid Mi-dicine • VOILIUJC 127 • Number 2
equations approach of Zeger and Liang (13). This approach inflates the standard errors to adjust for correlations in both independent variables (such as strength) and dependent variables (such as radiographic grade) within participants. Statistically significant differenees (P < 0.05) in the above analyses are specifically noted below. Results
The characteristics of the 462 men and women in the cohort are shown in Table 1. As expected, men were taller, were heavier, and had greater lowerextremity strength and lean tissue mass in the lower extremities compared with women (P < 0.001 for all comparisons). One hundred forty-five participants (31%; 33% of the women and 30% of the men) had radiographic evidence of osteoarthritis involving the tibiofemoral compartment, the patellofemoral compartment, or both. In 62 participants (43%), the radiographic changes were unilateral. Table 2 shows the association between osteoarthritis and obesity (14-16). Women in the cohort who had osteoarthritis were approximately 15% heavier than women with normal radiographs and no knee pain. Men with osteoarthritis were also slightly heavier than men without osteoarthritis. Among those with radiographic evidence of tibiofemora! osteoarthrilis, women were slightly more likely than men to report knee pain {P = 0.10; Table 3), Table 2 also shows the mean summed and the distribution of scores for left knee pain and functional impairment (data for the right knee were similar). Among men and women with radiographic
Table 1. Age, Height, Weight, and Lower-Extremity Strength and Lean Tissue Mass* Variable
Age, y Height, cm Weight, kg Concentric strength, Ib-ft Right lower extremity E;
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3. 1 I b 12 3 32.
3 2 6 3 1 1 -i 26 3
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oqiJiT L;5e was ds'inen ^> (ivp tmr-s o: more* ut'i weel O i';tforir'h'i' •, ol In;.' tibiolernor.al 'comprirtr-im:, pd'el'ijler O'^^l i: iSAiD^ - rioi'i'.e'o Jai ciri' -i-rl-in-irT-,-itoi-v d'uiri
100
226; 100)
! ' , V ' | ,ir|!)i".,"ii i,|l V v O r i ' f ' l
osteoarthritis). Functional impairmenl in participants who had pain but ni> radiographic evidence of osleoarlhritis also differed {P r J'M-'VIPI-I Imh. t Coinprir.-d wMh \'.a differt?n(.ir in ^.tr^nqth b.?T.*vOi_-ri (he dilei.lt'ii .jnrt iina:ipi= foi diiciet^' and ccfitinu'jui ouicomes Eiopietrics. 1986,42 121-30 Anderson JJ, Feison DT. l-ac:ori associated with osteoa-ir'i [-, u: ;he I urc lu :he first national Health atid Nufution r«amin,=itior SL.'vey (HANE^- I; Evidence
for an assot lation v.'iih cverweigh:, lace, a-.d vyi i.a- nen^a'^iis of work ,Am ; Epidemiol 1988,128 ;79-S9 15. Feison DT, Anderson JJ, Naimark A, Walker A M , Meenan RF. Obesitv and knee osteoarthnLis The Frdmingham Study Ann ^-lerr Med 1989:109 16. Davis MA, Ettinger WH, Neuhaus JM, Cho SA, Hauck WW. lhe ssso(ki'.ion of knee injuiv and obesity w t r ;jn,iaiera' and bilateial osteoa'th'itis ot • h,3^rlee Am , Epidemiol 1989, MO 273-38 17. Fisher NM, Kame VD Jr, Rouse L, Pendergast DR, Quantitative eva'_,ano^ of a '••••ruT'p exerrise program on 'iv^scie ana functional capaci'y ol patients witfi O5:f>oar:hn;is An- I P^ys Med Rc-.rib'' ' 994,^3 a i 3-20 18. Fuller NJ, Laskey MA, Elia M. Assessment o" I'.e co'noosi^on ot ma|oi body 'eg oni> by dual-energy i^rLiv t.io^i()''otiOir>etiv iE)E,XAi, v.'itn special refeii^r.ci to'q-Li mih^.lL' 'tia^sChn Fhvsiol 1992,12 253-66 19. Haarbo J, Gotfredsen A, Hassager C, Christiansen C. Body co-nuostio" by dual-energy x-ray absorp'tiometty lAhstracfl J Bone fvi-r- Res 1990, 20. Tataranni PA, Ravussin E, Jse ot dual energy x-iay -Hb;.orpli'omctiy in obese Tidividuals 'in" J C ••• Nutr 1995,62 73Ci-" 21. Rutherford O M , Jones DA, Newham DJ. C micai and e.'^penmental applica:ion ol lhe percLitaneous Uvtcb. supenmpositi'on :echnic|ue foi ihe st-^uy of l-iumari -i..:;,(..u artrvation i Neurol Neurosurg fbyO'.dl'y 1985,49'"288-9' 22. Jefferson RJ, Collins JJ, Whittle MW, Radin EL, O'Connor JJ, Ti-e role ot the cad^'CC-Di in co'"t%j, ng uTipulsivi.' toru". around heel "itnke I'roc Insl Mecli En(.i 1990,?0'i 71-8 23. Aitman R, Asch E. Bloch D, Bole G, Borenstein D, Brandt K, et aL Developitie'il ot cntena 'oi tfie ticiisificatiori and repoftirti of osteoar'hnns classification o' os:eoart-ritis of :he k-ee Anlint.s Ri-cuai 1986 29 1039-49.
24. Mazzuca SA, Brandt KD, Katz BP, Freund DA, Dittus RS, Lubitz RM, et al. R,L> ol ,.-!i'O!jenic gas^iouariiy f^OTi d'uOS prescribed by *amily physicians, 'je'^eis- iriternisti and rheumatologists for osteoartfint'i o' I'lc knee ^Ahsl-actj Arthritis Rnenm 1995,38 S227 25. Hadler NM. Knee pain i; t'le 'i'.,-:'aay- r'ol osteoa'-jmns ;Fditonal| Ann Intern Med 1992,1 i6 598-9 26. McAiindon TE. Snow S, Cooper C, Dieppe PA. Radiogiapfm: oat'em;, :>'. (j',:eoarthntis of ti'ie Knee .-o-^t m thr- co!Tit-..,,T.tv the iniport.^i'i.u o'" III-Lpaiello'cmoral o r t Ann Rneum Dii 1992,51 84-1-9 27. Sharma L, Dougherty C, Feison D. The Lireva:en!.e .if ijaii-'Ot'erno'ai and mixed ccimparimen'i involv^'menl ni >j"ee osteoa-i'^'.t^s anc thi^'ir otfects on 'unaional'.lat.r-, lAbstiact: J ^'-.vest Med 1996,'K'^59A
.. . Ctimp liospitals seemed like churclies which offer sanctuary tVom an all powcrl'LiI Inquisition; to break the code oi behavior wliich prevniled in them was equivalenl almost lo tlesecration: and although m;in was not worshipped in them, he was at least respected within ihe limits which allow him to distinguish punishment iVom toriare in prisons. Gustaw Herling A World .'iparl London: Joseph Heinernann; Submitted by; Bernard Kaminetsky. MD Boca Raton. FL 33433
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