Vol. 101809-9513 No. 2, 2006 ISSN Braz. J. Phys. Ther. Vol. 10, No. 2 (2006), 175-180 ©Revista Brasileira de Fisioterapia
Knee range of motion
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KNEE JOINT RANGE-OF-MOTION EVALUATION: CORRELATION BETWEEN MEASUREMENTS ACHIEVED USING A UNIVERSAL GONIOMETER AND AN ISOKINETIC DYNAMOMETER BATISTA LH 1, CAMARGO PR 1, AIELLO GV 1, OISHI J 2 & SALVINI TF 1 1
Muscle Plasticity Unit, Laboratory of Neurosciences, Department of Physical Therapy, Federal University of
São Carlos, São Carlos, SP - Brazil 2
Department of Statistics, Federal University of São Carlos, São Carlos, SP - Brazil
Correspondence to: Tania F. Salvini, Universidade Federal de São Carlos, Departamento de Fisioterapia, Rodovia Washington Luís, km 235, CEP 13565-905, São Carlos, SP - Brazil, e-mail:
[email protected] Received 15/02/2005 – Accepted: 30/11/2005
ABSTRACT Background: The instrument most often used by therapists for measuring joint range of motion (ROM) is the universal goniometer. However, there is a lack of studies analyzing the reliability of knee joint ROM measured by the isokinetic dynamometer. Objective: The purpose of this study was to analyze the correlation between the knee joint ROM measurements made using a universal goniometer and an isokinetic dynamometer. Method: 38 healthy volunteers (27 women, 11 men) aged 36 ± 11 years were evaluated. All of them had a minimum knee extension ROM limitation of 20°. Three knee ROM measurements were made using the universal goniometer and another three using the isokinetic dynamometer, on each subject’s dominant limb. Results: The results showed a high degree of correlation between the knee ROM measurements made using the two instruments (Pearson correlation coefficient = 0.90). Conclusion: From the procedures performed, both the universal goniometer and the isokinetic dynamometer can be used to evaluate knee ROM, since they both present reliable measurements. Key words: goniometer, isokinetic dynamometer, knee, ROM.
INTRODUCTION Measurement of the range of motion (ROM) of a joint is an important component of a physical evaluation, since it identifies the limits of a joint and allows for the professionals to accompany the efficiency of interventions in a quantitative way during rehabilitation. The universal goniometer1 is the instrument most widely used by therapists to measure ROM, although other instruments, such as the isokinetic dynamometer2 can also measure ROM. There has been a considerable increase in the use of this latter instrument over the last few decades including by physical therapists, who have benefited in a particular and significant way from the use of this technology3. In order to correlate the universal goniometer with the isokinetic dynamometer so that both can be used to measure ROM, they must both provide reliable measurements. According to Dvir3, the reliability of a measurement is the consistency between successive measurements of the same variable for the same subject under the same conditions. The author also stated that there were three sources of error
that could make an evaluation unreliable: the measurement instrument itself, the person who directs the evaluation and different characteristics of the volunteers being evaluated, the latter undoubtedly being the most difficult error to control. Considering individual differences, the measurements obtained using a determined equipment can vary, and thus the reliability of the measurements can only be confirmed by applying specific statistical tests3,4,5. Described in the literature since 1914, goniometry is widely used in both clinical practice and scientific research, with the objective of measuring the ROM of a variety of joints. Various experiments have examined the degree of reliability of goniometric measurements by way of different measurement procedures, and demonstrated that ROM measurements of the knee carried out using the universal goniometer showed a good to excellent degree of reliability6-14. Other studies only considered the measurements made with the universal goniometer to be valid after correlating them with the ROM measurements obtained by radiography, considered to be a well established standard measurement11,12,14.
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Thus the universal goniometer is an instrument that can be used to obtain reliable, valid measurements of knee ROM. However, Ellis & Bruton15 concluded that the hand joint ROM measurements made with the goniometer were more reliable when only one measurement was involved, than when multiple joint measurements were required. Brosseau14 reported that the goniometric measurements of knee ROM were more reliable when carried out by a single evaluator. In a recent study, Aalto8 observed that the measurements of the knee joint made with the goniometer were not very reliable, but in compensation commented that the position used in the test may have contributed to the result. Finally, as a joint measurement instrument, the goniometer is more reliable16 and valid14 than a visual estimation. The isokinetic dynamometer can also be used to measure the ROM of various body segments, this being a computerized piece of equipment widely used in the functional evaluation of the musculoskeletal system. However there is a lack of studies in the literature analysing the reliability of ROM measurements carried out using the isokinetic dynamometer. Considering that the knee joint is one of the most injured joints of the human body, different procedures are used to measure knee ROM. The therapist can make such measurements using a manual universal goniometer or using computerized instruments such as the isokinetic dynamometer. Thus it is important to check if the measurements provided by these two instruments can be correlated with each other. The objective of the present study was to analyse the degree of correlation between the measurements of knee extension ROM obtained by a therapist using the universal goniometer, and those obtained using the isokinetic dynamometer. METHODOLOGY Volunteers Thirty-eight healthy volunteers of both sexes (27 women and 11 men), aged 36 ± 11 years old, took part in this study. As an inclusion criterion, the volunteer had to present a 20º limit in knee extension range of motion17 of the dominant limb measured using the universal goniometer, with the subject lying on his back with the hip and knee joints flexed at 90º13. All the volunteers were informed of the study objectives and procedures and signed a consent form according to resolution 196/96 of the National Health Council. The Ethics Commission for Research with Humans of the University approved the study. Instrumentation A plastic universal goniometer (Carci) and an isokinetic dynamometer (Biodex Multi-joint System 3) were used to evaluate knee extension ROM.
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Procedures Measurement of knee extension ROM using a universal goniometer With the aim of decreasing possible differences in the evaluations by the therapist, two physical therapists were first trained and then carried out all the knee ROM evaluations using the universal goniometer and isokinetic dynamometer designated for this study. With the individuals in the dorsal position, a test was first carried out to check for shortening of the hip flexor muscles, as described by Kendall 17, which could cause compensations such as the pelvic tilt, and alter the knee ROM measurements. Thus in individuals showing shortening of the hip flexors, the knee joint of the contra-lateral limb was flexed, maintaining the pelvis in a neutral position with the aid of a pad, to avoid compensations (Figure 1).
0°
Terminal Position
* Figure 1. Evaluation of knee extension ROM using the universal goniometer (indicated with arrowhead) indicating shortening of the knee flexor muscles. The ROM measurement was made when the subject noticed the start of knee flexor muscle tension. A pad (*) was used for subjects with shortened hip flexors to flex the contra-lateral limb and thus maintain the pelvis in a neutral position.
For the initial evaluation, the hip and knee of the dominant limb were flexed at 90º and the foot maintained in a relaxed position13. As from this position, evaluator 1 passively and slowly extended the knee, while evaluator 2 certified that no compensations were occurring. The volunteer was instructed to relax during the evaluation, especially when the knee was being extended, and to report the moment at which he felt the start of tension in the knee flexor muscles, which was considered to be the final position (Figure 1). Having reached this position, evaluator 1 measured the degree of shortening of the knee flexors, that is, knee extension, using the universal goniometer (Figure 1) as described by Norkin
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& White1. Complete knee extension was considered to be 0º13 and used as the reference to calculate the degree of limitation of the knee joint extension. The knee extension ROM measurement of each individual was evaluated three times, and the arithmetic mean of the three measurements used in the calculations.
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the lateral epicondyle of the femur and the leg fixed to the resistance arm of the dynamometer, maintaining the ankle joint free. Before starting the evaluation, the volunteer received a manual device connected to the dynamometer (Figure 2), with which he could start or stop the passive evaluation being carried out. He was then instructed to shut his eyes and remain relaxed. He should then switch on the dynamometer using the manual device, such that the resistance arm of the equipment would start to passively extend the knee at a speed of 2º/s. During this phase, the volunteer was instructed to remain completely passive to the movement and to stop the resistance arm using the device as soon as he felt the start of stretching tension in the knee flexor muscles, in order to measure the extension ROM of this joint. Three consecutive measurements of this movement were made and the arithmetic mean used in the statistical analyses.
Measurement of knee extension ROM using an isokinetic dynamometer A cushioned accessory was attached to the back of the dynamometer chair to maintain the hip of the volunteer flexed at approximately 90º (Figure 2). This procedure guaranteed that the same neutral pelvis position used during the knee ROM evaluation using the goniometer, was maintained during the measurements made using the dynamometer. The volunteer was stabilised in the dynamometer chair using straps round the trunk, hips and the thigh of the dominant limb under evaluation (Figure 2). The rotating mechanical axis of the dynamometer was then aligned with
Statistical analyses The coefficient of variation (CV) was first used to estimate the percent variation between the first, second and third measurements of knee extension ROM obtained with the two evaluation instruments under study. The reliability and correlation of the measurements of knee ROM carried out using the goniometer and dynamometer were statistically analysed by way of the following tests: Coefficient of Variation (CV) and Pearson’s Correlation Coefficient (PCC). The CV was applied to determine inter-volunteer and intra-volunteer variation. For each evaluation instrument, the inter-volunteer CV was considered as the reference for the intra-volunteer CV, according to Rothstein9 and Norkin & White1. It was considered that PCC values from 0.90 to 0.99 corresponded to high correlation, from 0.80 to 0.89 to good correlation, from 0.70 to 0.79 to little correlation and values ≤ 0.69 to low correlation18.
*
RESULTS It can be seen from the results presented in Table 1 that for both instruments, the CV for the first measurement was bigger than those for the last two measurements, being slightly larger for the dynamometer, although this difference was not significant. It can also be observed that, in general, the values
Figure 2. Positioning of the volunteer in the dynamometer chair: stabilization straps (∆), device (arrow) used to start and stop the passive evaluation, and accessory (*) used to maintain hip flexion at about 90º.
Table 1. Measurements of knee extension ROM made using the universal goniometer and the isokinetic dynamometer for 38 subjects. Universal Goniometer Measurements X ± SD
CV
1st
Isokinetic Dynamometer 2nd
3rd
1st
2nd
3rd
44.5 ± 12.1° 45.0 ± 11.9° 44.9 ± 11.8° 46.3 ± 15.4° 46.6 ± 13.6° 45.8 ± 14.0° 27.2%
26.4%
26.4%
33.1%
29.2%
30.6%
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Table 2. Comparison of the inter-volunteer and intra-volunteer CVs for the evaluation of knee extension ROM, carried out using the universal goniometer and the isokinetic dynamometer for 38 subjects. ▲
▲
DP g
CV
44.8° 10.7°
1.8°
23.9% 4.0%
Dynamometer 46.2° 12.6°
3.7°
27.2% 8.0%
X Goniometer
DP
CVg
G O N I O M E T E R (degree)
X = mean; SD = standard deviation; CV = coefficient of variation; p inter-volunteer, n intra-volunteer.
80 60 40 20 0 0
20
40
60
80
D Y N A M O M ET ER (degr ee )
Figure 3. Pearson’s correlation coefficient values (r=0.90) between the knee extension ROM measurements obtained using the universal goniometer and those obtained using the isokinetic dynamometer for 38 subjects.
for CV for the three evaluations made with the isokinetic dynamometer varied more than those made with the universal goniometer. For the two instruments, the results showed that the intra-volunteer CV obtained for the evaluation of joint ROM, was smaller than the inter-volunteer CV (Table 2). Pearson’s correlation coefficient indicated a high degree of correlation (0.90; p< 0.05) between the means obtained with the goniometer and those obtained with the dynamometer (Figure 3). DISCUSSION Considering the experimental conditions used, the results of the present study showed high correlation between the means obtained for knee extension ROM using the universal goniometer and those obtained using the isokinetic dynamometer. Studies have used the universal goniometer to test the reliability of ROM measurements of various joints made using different instruments14,19-21, but no studies were found in the literature using the universal goniometer to test correlation with knee ROM measurements made using the isokinetic dynamometer. Thus to our knowledge, the results reported in this study are inedited in the literature.
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It was observed that for both the goniometer and the dynamometer, the values for the intra-volunteer CV of the measurements were smaller than those of the inter-volunteer CV. According to Rothstein9 and Norkin & White1, this indicates that the measurements of knee ROM made with both instruments were reliable. Thus good reliability was shown for both the measurements made manually by the therapist with the universal goniometer and those made using the isokinetic dynamometer (Table 2). Nevertheless, some aspects observed need to be considered. The results indicated a difference between the CV values obtained for the measurements made with the goniometer and those for measurements made with the dynamometer (Table 2). The inter-volunteer and intra-volunteer CVs for the measurements obtained with the dynamometer were larger than those obtained with the goniometer. According to Norkin & White1, various factors can alter the degree of reliability of a measurement. In this study, such factors were considered so that the procedures carried out during the measurement of knee extensor ROM using the dynamometer were as close as possible to the procedures used during measurement using the goniometer, as follows: both measurement methods were carried out by the same evaluators, both forms of evaluation maintained the hip joint flexed at approximately 90º, knee joint ROM was measured passively in both cases and the same number of repetitions were used. Although all these precautions were taken with the objective of minimising possible differences in procedure between the two instruments, it was observed that measurements made with the isokinetic dynamometer varied more than those made with the universal goniometer. According to the volunteers, this difference could have occurred due to the greater difficulty in determining the start of knee flexor muscle tension during the measurement of ROM using the dynamometer. This difficulty was probably the cause of the greater variation between the ROM measurements made using this equipment as compared to those made using the universal goniometer. This result indicated the need for a greater number of repetitions when evaluating joint ROM using the isokinetic dynamometer. This suggestion was reinforced by the results shown in Table 1 showing the CVs of the three evaluations for the two instruments. It can be observed that the first evaluation varied more than the subsequent evaluations, independent of the instrument used, although this variability was greater in the case of the isokinetic dynamomter. This result demonstrates the need to familiarise the volunteers with the instruments before carrying out the tests, especially in the case of the dynamometer. It is important to note that during the present study it was observed that 20% of the volunteers presented alterations in their perception of knee flexor muscle tension, with a mean variation of 22º between the measurements made with the
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goniometer and those made with the dynamometer, whilst 80% only varied 4º. The first group of volunteers (20%) were re-evaluated using the same position for making the measurements, that is, both the measurements made using the goniometer and those made using the dynamometer were obtained in the seated position. The variation between the measurements of knee extension ROM changed from 22º to 6º. Considering this result, it appears that the great difficulty in perception presented by 20% of the volunteers was related to the measurement position. Thus it must be considered that the position alters the perception of some volunteers and that this difficulty could alter the final analysis of the measurements obtained with these instruments. Having proved the reliability of the measurements made with both instruments, they could then be correlated. The value obtained for the Pearson’s correlation coefficient (PCC) indicated a high degree of correlation between the measurements obtained with the two instruments. Thus both the values for CV and for PCC showed a high degree of reliability of the measurements obtained with the two instruments and between them. These results did not corroborate those found by Farber et al.21, who observed that the measurements of joint ankle obtained with a computerised equipment were more reliable than those obtained with a goniometer. As in other studies, some using different measurement procedures14,22 and others using the same procedure13,23,24, the present study showed that the goniometer could be used to carry out measurements of knee extension ROM. In addition the results of the present study demonstrated that the isokinetic dynamometer could also be used to evaluate knee extension ROM. CONCLUSIONS Considering the procedures used in the present study, both the universal goniometer and the isokinetic dynamometer can be used to evaluate knee ROM, since their measurements are reliable. Acknowledgements: This project received financial support from FAPESP and from CNPq. Batista LH and Camargo PR, were awarded Masters scholarships by CAPES. Aiello GV received a placement scholarship from PIBIC-CNPq.
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