WALKING TIME MEASURES FOR EVALUATING OA OF THE KNEE f ABSTRACT ' This study assessed the test-retest re liability a nd the sensitivity of self- p a c e d walking tim e measurements for evaluating the functional per fo rm a n c e o f persons w ith knee osteoarthritis (OA). The 13 m tim ed walking tests were carried out on tw o separate occasions over a six w eek period for 10 patients using a standardised protocol. The same measurements were recorded also for three additional patients before and after a six w eek quadriceps strength training regimen. As indi c a te d by an intraclass correlation co e fficie n t o f 0.83 with no signifi c a n t intersession test differences for the group (P=0.98), the g a it meas urements were reliable. However, despite m arked increase in knee extensor strength and significant subjective improvements in walking tim e for the three experim ental sub jects were smaller than the error of measurement. The findings suggest th a t regardless of reliability, meas urements of self-paced level walk ing tim e m ight not be sufficiently sensitive for evaluating longitudinal changes in functional'perform ance i in this patie n t population. RELIABILITY AND SENSITIVITY OF SELF-PACED WALKING TIME FOR ASSESSING FUNCTIONAL CAPACITY IN PERSONS WITH OSTEOARTHRITIS OF THE KNEE by R M arks, Osteoarthritis Research Centre, Toronto INTRODUCTION Although kinematic measures of walk ing time continue to be used for judging the efficacy of treatments for osteoarthritis (OA) of the Knee1’7, no study to date has specifically investigated w hether these measurements are reliable and sensitive to change in this patient population. Given the constantly fluctuating symptomatol ogy of OA8, it is of utmost importance to ensure that interval changes in walking time can be confidently attributed to a true change in clinical status of the patient9. It is equally important to ensure that walking time measurements designed to evaluate the efficacy of treatments for this condition are sensitive indicators of a change in func tional status. The purpose of this study was to exam ine the reliability of m easurem ents of walking time for persons with stable knee OA over a six week period. A second pur pose was to aid the clinician and/or inves tigator in determining whether measure ments of walking time would be suffi ciently sensitive for determining the effi cacy of treatments other than surgery for patients with knee OA. PATIENTS AND METHODS Patients The patients in this prospective study were 10 women aged 54-76 years (mean 65.90 approx 8.34), h eight 155-167 cm (mean 161.9 approx 3.31) and weight 63- 113 kg (mean 76.01 approx 15.28) who ful filled the clinical and radiological criteria of the American College of Rheumatology (ARA) for the diagnosis of OA of the knee1 . In addition, three patients, age range 53-62 years, who fulfilled the ARA criteria were studied before and after com pletion of a six week isometric quadriceps strength training program. At study entry all participants complained of pain o n ’ walking. Fifty per cent were receiving non steroidal anti-inflammatory drugs for their arthritis and none used walking aids. As indicated by an average score of 12.80 ap prox 3.11 on The Lequesne Index of Dis ease Severity of Knee OA or ISK12, the cohorts studied w ere sev erely hand i capped. The protocol was approved by a University Ethics Committee and all par ticipants provided informed consent. Procedures The walking time measurements were carried out indoors on level ground using a stop watch. To allow a subject to walk at constant speed on the walkway and to con trol for the effects of acceleration and de celeration, subjects were instructed to walk with ordinary shoes at their normal com fortable walking pace for a distance of 3 m before walking time was recorded. The standardised procedures were carried out by the same observer six weeks later under the same theoretical no change conditions for the control group and after the six weeks of exercises for the experimental group. Statistical methods The statistics used to describe the data were the mean and standard deviation (SD). Reliability (R) was computed with intraclass correlation coefficients (ICCs) (1,1)14. In addition, the standard error of the mean or SEM which represents the 68 percen t confidence interval about the mean was computed from the reliability data as suggested by Hayes15. To assess the statistical significance of learning on the repeated measurements, a dependent t- test was used. Differences in walking time, maximal isom etric qu ad ricep s torque and ISK scores at baseline and after six weeks of quadriceps strength training w ere ex pressed as a percentage of the baseline scores (see Table I). Pre- and post-exercise data were also compared using paired t- tests and Pearson correlations. The level of significance for the analyses was set at P. RESULTS Reliability The means, standard deviations and the 95 percent confidence intervals about the mean calculated for the walking tests are reported in Table II (page 7). As shown, the ICC or R statistic for the tests was 0.83 with a SEM of 1.50 seconds. As indicated by a Student's t-test there was no systematic learning effect with repeated testing. Sensitivity Although accompanied by a 4-8 percent improvement in walking time after exer cise which correlated positively with indi vidual increases of quadriceps strength (r=0.90), this improvement was not signifi cant (t=2.05, p=0.17) and remained within the possible error of measurement of 1.50 seconds (see Table I page 7). The ISK scores which were also positively correlated with the walking time scores post-intervention (r=0.86) were, however, significantly im proved (t-8.66, p=0.01). Continued on page 7 .. . Physiotherapy.; February 1994 Vot 50 No 1 P a g e d R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) MEDIO - TRONICS (Pty) LTD SPECIALIST SUPPLIERS TO THE PHYSIOTHERAPIST ELECTROTHERAPY MADE SIMPLE, EFFECTIVE & COST EFFICIENT ENDOMED 382 • 2 and 4 pole interferential • 3 Muscle stimulating programmes • 15 Pre programmed treatment options • Can be connected to VACOTRON 360 for suction electrode application SONOPULS 390 -1/3 • 1 MHz or 3 MHz ultrasound units • Continuous or pulsed ultrasound • 10 additional pre-programmed treatment options • Ultrasound heads have contact control • Unit complete with small or large ultrasound head ENDOMED 381 AC • 2 Pole interferential therapy • 5 TENS currents • 3 muscle stimulating programmes • 15 pre-programmed treatment options • can be connected to VACOTRON 360 All th e a b o v e units h a v eENRAF 3 s te p o p e ra tio n o p tio n a l c a rry h a n d le 2 y e a r w a rra n ty T U V / G S a n d lE C 601-1 a p p ro v a l Head O ffice: Delft House, 376 Rivonia Boulevard, Sandton. Tel (011) 803-9320/1/2/3 Telefax (011) 803-7085 Cape O ffice: 18 Vlei Str. Bellville, Cape. Tel (021) 946-4560/1 Telefax (021) 948-8401 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) .. Continued from page 5 DISCUSSION Table 1: Summary of post-exercise im provements in walking time Subject Walking Quadriceps ISK time torque at 60° scores* (secs) Flexion (Nm) 1 0.6 (8%) 31 (75%) 6 (66%) 2 1.0 (7.6%) 85 (60%) 4 (56%) 3 0.4 (4%) 22 (30%) 5 (29%) Abbreviations: Nm = Newton Metres ISK = Index of knee severity * Significantly improved Table II: Mean, standard deviation, 95% confidence limit about the mean, and in- traclass correlation coefficient Week 1 Week 6 Mean 12.33 12.35 SD 3.37 2.85 95% 12.33+1.50 12.35+1.50 CL 0.83 ICC P 0.98 Statistical test: Dependent t-test Free walking velocity, which is often subnorm al in persons with OA of the knee10'13'18'19 is frequently used for the ob jective evaluation of therapeutic regimes for this condition1,2,5'19 or for identifying p ro b lem s d u rin g am b u latio n 6,7,10, 3,1 . How ever, despite the w idespread and continued use of this measurement for ob jectively assessing functional capacity, there are no studies concerning possible changes in measurements of self-paced walking time due to the repetition of the test nor any estimates of the measurement error associated with such tests. Equally important in evaluative research is the cri terion of instrum ent responsiveness or sensitivity to change20 and this aspect has not been the subject of any previous study of this measurement for this group. In accordance with the high intra-ob server reliability reported , for the 50-foot walking test in patients with rheumatoid arthritis16,17, the present measurements of self-paced walking time were performed with high reliability across sessions (see Table II). The reliability of the tests was supported also by the finding of no signifi cant measurement differences across ses sions and a low SEM. The high inter-day reliability of the measurements contrasted with those ob tained from other commonly used out come measures for evaluating treatment effects in this population, such as radio- graphic and laboratory measures. The measurements were also easy to perform, required no special setting other than an illuminated walkway and were obtained with minimal time commitment on the part of the researcher. It is also expected that since the measurements are easily stan d ard ised that d ifferen t observ ers would achieve a similar result. However, in spite of significant meas urement reliability and statistically signifi cant improvements on a validated subjec tive index in three cases undergoing exer cise therapy, the trend towards improve ment in walking time in this subgroup of patients (t=2.05, n-3, p-0.17) fell within the limits of normal variability of the measure ment, suggesting poor measurement sen sitivity. Although this has been implied for rheumatoid arthritic trials16, a small sam ple with limited power might reduce the ability to detect statistically significant dif ferences in walking time before and after treatment, even if these actually exist, re sulting in a beta error. In addition, the d u ra tio n or in te n s ity o f the cu rre n t strengthening program might have been insufficient. Improvements in walking speed might also be expected to be more evident follow ing the effects of treatments such as uni compartmental prosthetic knee replace ments as suggested by the findings of Mattsson et al for 19 of 20 patients with moderate knee OA. They not only found an individual change in the parameters of self-selected walking speed for these pa tients postsurgery, confirming the sensi tivity of the measurements, but also re ported that the improvements in walking tim e w ere correlated w ith favourable changes in single limb support time, indi cating measurement validity. This was in line with the findings of Stauffer et al13 who reported significant correlations between the variable of gait velocity and those of pain, range of motion, walking distance, sitting and rising from a chair and instabil ity in 65 patients with degenerative joint disease examined preoperatively. Based on a study of patients with OA of the knee who underwent total knee arthroplasty, Collopy et al25 postulated that strength of the knee extensor muscles was related to free walking velocity which they reported was a sensitive indicator of functional per formance. However, the usefulness o f walking time measurements for measuring clinical improvements in knee function was not supported for persons with knee OA fol lowing drug therapy despite clinical im provements in rest pain, knee range of mo tion and stiffness. Lack of measurement sensitivity might also serve to explain the outcome of a controlled study of fenopro- fen therapy in geriatric patients with knee OA in which the time required to walk 50 feet was the only parameter demonstrat ing insignificant improvement1. This was also the finding with post-test baseline comparisons in free velocity reported by Peterson et al19 which failed to achieve sig nificance when intervention (n=47) and control groups (n=44) of patients with knee OA were compared after an eight-week program of physical exercise, which in cluded strengthening. Thus, while walk ing tests appear useful for assessing the locomotor handicap occurring in O A of the knee postsurgery ,6,7 doubt arises as to their utility for assessing the efficacy of more conservative therapies such as drugs and exercise for the treatment of this con d itio n . T h is w as a lso the co n clu sio n reached by Grace et allb for persons with rheumatoid arthritis. These data suggest that inasmuch as the goal of physiotherapy for knee OA is to improve function, that due to their poor responsiveness, m easurem ents o f self- paced walking may prove inaccurate for monitoring longitudinal changes in func tional ability in this group of patients, de spite their reliability, practicality and cost- effectiveness. Pending further research us ing a larger sample, it is therefore recom mended that to ensure important thera peutic changes are not overlooked in trials designed to evaluate efficacy for individu als with knee OA, validated tools such as the ISK be used concurrently for measur ing functional capacity. ACKNOWLEDGEMENTS This study was funded by The Arthritis Society, Toronto. REFERENCES 1. M cM aho n F, Ja in A , O nel A. C o ntrolled ev alu ation o f fenop rofen in g eriatric p atients w ith osteoarthritis. / R heu m atol 1976;2(Su p p l):76- 82. 2. C im m in o M , C u to lo M , Sam an ta et al. Sh ort term treatm en t o f o steoarthritis: A co m p ari son o f sodium m eclo fen a m a te and ibu p ro- fen. / In t M ed R es 1982;10:46-52. 3. S ch an k JA , H erdm an S J, B lo y er R G . P h ysical T herap y in the m u ltid iscip lin ary assessm en t and m a n ag em en t o f o steoarthritis. C linical T herapeutics 1986;9(Su p p l B):14-23. 4. Ste in e r M E , Sim o n S R , P isciotta JC . Early ch anges in g ait an d m axim u m kn ee torque fo llo w in g k n e e arth ro p la sty . C lin O r th o p 1988;238:174-182. 5. Blin O , P ailh ous J , L affo rq u e P et al. Q u an tita tiv e an aly sis o f w a lk in g in p atien ts w ith knee osteoarthritis: a m eth od o f assessin g the ef fectiven ess o f no n -stero id al anti-in flam m a tory treatm ent. A n n R heum D is 1990;49:990- 993. 6. M attsso n E, O lsso n E , B rostrom L. A ssessm ent o f w alkin g be fo re and a fter un ico m p artm en tal knee arth rop lasty. A co m p ariso n o f differ en t m eth od s. S can d J R ehabil M ed 1990;22:45- 50. 7. M attsson E , B rostrom L. T h e p h ysical and continued on page 8... Physiotherapy February 1994 Vol 50 No 1 Page 7 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) p s y c h o s o c i a l e f f e c t o f m o d e r a t e o s l e o a r l h r o s i s o f t h e k n e e . S c a n d j R c h a b il M e d 1 9 9 1 ; 2 3 : 2 1 5 - 2 1 8 . S. B e l l a m y N W , B u c h a n a n W W , G o l d s m i t h C H ii a l . V a l i d a t i o n s t u d y o f W O M A C : A h e a l t h s t a t u s i n s t r u m e n t f o r m e a s u r i n g c l i n i c a l l y i m p o r t a n t r e l e v a n t o u t c o m e s to a n t i r h e u m a t i c d r u g t h e r a p y i n p a t i e n t s w i t h o s t e o a r t h r i t i s o f t h e h i p o r k n e e . / R h e u m a t o l 1 9 8 8 ; 1 5 : 1 8 3 3 - 1 8 4 0 . 9 . C o w e l l H R . E d i t o r i a l . R a d i o g r a p h i c m e a s u r e m e n t s a n d c l i n i c a l d e c i s i o n s . j H o n e j o i n t Snr\; 1 9 9 0 ; 7 2 A : 3 1 9 . 1 0 . F a l c o n e r J , H a y e s K W . A s i m p l e m e t h o d to m e a s u r e g a i t f o r u s e i n a r t h r i t i s c l i n i c a l r e s e a r c h . A r t h r i t i s C a r e R e s 1 9 9 1 ; 4 : 5 2 - 5 7 . 1 1 . A l t m a n R D . C l a s s i f i c a t i o n o f d i s e a s e s : o s t e o a r t h r i t i s . S e m i n A r t h r i t i s R h e u m 1 9 9 1 ; 2 0 ( S u p p l 2 ) : 4 0 - 4 7 . 1 2 . L e q u e s n e M , M e r y C , S a m s o n M e l a l. I n d e x e s o f s e v e r i t y f o r o s t e o a r t h r i t i s o f t h e h i p a n d k n e e . V a l i d a t i o n . V a l u e in c o m p a r i s o n w i t h o t h e r a s s e s s m e n t t e s t s . S c a n d j R h e u m a t o l 1 9 8 7 ; ( S u p p l 6 5 ) : 8 5 - 8 9 . 1 3 . S t a u f f e r R N , C h a o E Y S , G y o r y A N . B i o m e c h a n i c a l g a i t a n a l y s i s o f t h e d i s e a s e j o i n t . C li n O r t h o p 1 1>7 7 ;1 2 6 : 2 4 6 - 2 5 5 . 1 4. S h r o u t P E , F l e i s s J L . I n t r a c l a s s c o r r e l a t i o n s : u s e s i n a s s e s s i n g r a t e r r e l i a b i l i t y . I ’s i / c h o l H u ll 1 9 7 9 ; 8 6 : 4 2 0 - 4 2 8 . 1 5. H a y e s K W . T h e e f f e c t o f t h e a w a r e n e s s o f m e a s u r e m e n t e r r o r o n p h y s i c a l t h e r a p i s t s ' c o n f i d e n c e i n t h e i r d e c i s i o n s . I’ l l i/s T h e r 1 9 9 2 ; 7 2 : 5 1 5 - 5 3 1 . 16. G r a c e E M , G e r e c z E M , K a s s a m Y M e l a l. 5 0 - f o o t w a l k i n g t i m e : a c r i t i c a l a s s e s s m e n t o f a n o u t c o m e m e a s u r e in c l i n i c a l t h e r a p e u t i c t r i a l s o f a n t i r h e u m a t i c d r u g s . Hr / R h e u m a t o l 1 9 8 8 ; 2 7 : 3 7 2 - 3 7 4 . 17. P i n c u s T , B r o o k s R h , C a l l a h a n L F . R e l i a b i l i t y o f g r i p s t r e n g t h , w a l k i n g t i m e a n d b u t t o n t e s t p e r f o r m e d a c c o r d i n g t o a s t a n d a r d p r o t o c o l . j R h e u m a t o l 1 9 9 1 ; 1 8 : 9 9 7 - 1 0 0 0 . 18. I v a r s s o n 1, L a r s s o n L E . G a i t a n a l y s i s in p a t i e n t s w i t h g o n a r t h r o s i s t r e a t e d b v h i g h t i b i a I o s t e o t o m y . C l i n O r t h o p 1 9 8 9 ; 2 3 8 : 1 8 5 - 1 9 0 . 19. P e t e r s o n M C . E , K o v a r - T o l e d a n o P A , O t i s J C e l a l . E f f e c t o f a w a l k i n g p r o g r a m o n g a i t c h a r a c t e r i s t i c s in p a t i e n t s w i t h o s t e o a r t h r i t i s . A r t h r i t i s C a r e R e s 1 9 9 3 ; 6 : 1 1 - 1 6 . 2 0 . L a n k h o r s t G J , v a n d e r S t a n d t R J, v a n d e r K o r s t J K . T h e r e l a t i o n s h i p s o f f u n c t i o n a l c a p a c i t y , p a i n , a n d i s o m e t r i c a n d i s o k i n e t i c t o r q u e in o s t e o a r t h r o s i s o l t h e k n e e . S c a m l j R e h a b M e d 1 9 8 5 ; 1 7 : 1 6 7 - 1 7 2 . 2 1 . C o l l o p y M C , M u r r a y M P , G a r d n e r G M e l a l. K i n e s i o l o g i c m e a s u r e m e n t s o f f u n c t i o n a l p e r f o r m a n c e b e f o r e a n d a f t e r g e o m e t r i c t o ta l k n e e r e p l a c e m e n t . O n e - y e a r f o l l o w - u p o f t w e n t y c a s e s . C li n O r f / / » / H 9 7 7 ; 1 2 6 : 1 9 A - 2 0 2 . 1 REMEDIAL EXERCISER Sizes Available - Extra light, light, Medium, Heavy, Extra Heavy ADDING TO YOUR PROFESSIONALISM & SUPPORT YOUR PATIENTS L.C.C. CONTACT P.O. BOX 1655 NIGEL NORTHRIDING PHONE (011) 2162 474-3167 w O G R A D Y P E Y T O N international USA CALLING EXCELLENT OPPORTUNITIES $ 2 , 0 0 0 SIGN-ON BONUS P H Y SIO T H E R A P IST S! 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