Documentation of joint range of motion (ROM) helps the clinician to assess limitations that may be present and hence plan the most appropriate treatment strategy. Assessment of joint ROM may also facilitate evaluation of treatment and development of protocols for appropriate intervention. A variety of measurement tools are currently available, ranging from simple visual estimation to advanced three-dimensional video recording systems.1–3 The most practical and most frequently used clinical tool is the goniometer, and several different designs have been developed over the years. The simplest and most inexpensive type is the universal goniometer (UG). For measurements obtained using the UG to be clinically useful, results must be accurate and reliable.
Intratester reliability is important as the same clinician may take the same measurement on different occasions to document change. In the clinical setting, however, more than one tester may be involved in the measurement. Because this has potential for further error, intertester reliability must also be considered clinically relevant.
Several factors may affect the reliability of the measurements obtained using the UG. Reliability might vary between different joints as each joint has different characteristics. Arguably, this may make it easier or harder to obtain reliable measurements depending on the joint measured.4–9
The type of movement measured may also affect reliability, and reliability of active movements may differ when compared with passive movements, as if the force applied by the therapist to move the joint varies, this may cause different angles to be obtained each time measurements are taken.9 In addition, following a standard instruction procedure and prior training may affect the reliability as this minimizes the error associated with different procedures.
Different pathologies, such as upper motor neuron disorders, may influence the UG reliability. Upper motor neuron disorders may cause altered muscle function leading to variation in muscle tone. Hypertonicity and spasticity may have an effect on the ability to define end range of joint motion, which in return may affect the reliability of the measurements. In addition, the presence of bony deformations may cause difficulties in clearly identifying bony landmarks, which may compromise the reliability of measurements.
It is essential to understand how reliability may be affected when such variables are introduced because incorrect interpretation of measurements obtained may lead to inappropriate treatment. The aims of this review were therefore to investigate the intratester and intertester reliability of the UG and to examine how different factors influence measurement reliability.
An electronic and manual literature search was conducted to investigate the intratester and intertester reliability of the UG for measurement of lower-limb joints. A variety of search terms was used to search different medical and engineering databases such as Medline, Embase, NHS Scotland e-library, Science Direct, PubMed, and Google Scholar. Search terms included the following: reliability and/or universal goniometer; universal goniometer; goniome* measurement reliability; intertester reliability of universal goniometer or UG; and intratester reliability of universal goniometer or UG. Identified secondary references from the articles were found, and related books were also reviewed.
The review investigated the reliability of the UG in measuring ROM of the lower limb. Inclusion criteria were as follows: studies that evaluated intratester reliability and/or intertester reliability of the UG; studies that included patients and/or healthy subjects; studies that measured hip, knee, ankle, and/or subtalar joint; and studies that used intraclass correlation coefficient (ICC) to calculate reliability. Exclusion criteria included the following: studies that only investigated measurement of the upper limb and studies that did not use ICC to calculate the reliability. References from 1980 to present (July 2015) were included to ensure that the number of the studies was manageable.
Articles sourced were graded according to the Scottish Intercollegiate Guideline Network (SIGN) guidelines,10 and thematic tables of evidence were constructed for each design of goniometer and the pathology of the subjects tested.
Different statistical methods are used to measure the reliability, such as ICC, Pearson product moment correlation coefficient, analysis of variance reliability, coefficient of variation, and generalizability theory. However, this review concentrated on articles that used ICC values to calculate reliability. This method was considered the most appropriate method for reliability measurement as data are centered and scaled using a pooled mean and standard. In addition, as the correlation line between the values is drawn at a 45° angle, this was considered to reflect the most accurate reliability value.11,12 Most studies did not report the reason for the chosen method of analysis, although one article stated that ICC best reflected errors associated with measurements.13 It has been suggested that the Pearson product moment correlation coefficient may produce high reliability values even when large inconsistency between paired scores is found.14 This statistical method may overestimate reliability as each variable is centered and scaled by its own mean and standard deviation. In addition, the correlation line is drawn at its best position without specifying location.11
The initial search yielded 71 articles, of which 21 matched the inclusion criteria and were fully reviewed.4–7,9,13,15–29 All the studies were case series (SIGN grade 3).
Intraclass correlation coefficient (reliability) values were rated as weak (0–0.60), good (0.60–0.80), or excellent (above 0.80).12,15,16,30,31 Three articles reported on intratester reliability only.4,6,21 Five studies reported on intertester reliability only.5,7,20,25,29 Thirteen articles reported on both intratester and intertester reliability (Tables 1–3).9,13,15–19,22–24,26–28
MOTION MEASURED AND MEASUREMENT PROCEDURE
Eighteen studies examined passive motion4–7,9,13,15–18,21,23–29 and three studies examined active motion.19,20,22 Four studies did not give testers standard instructions to follow or prior training.13,15,16,19
Seven studies included healthy subjects,7,20,21,25–28 whereas 11 studies included patients with various pathologies including diabetes,17 neurological conditions,4,5,9,22–24 orthopedic conditions,19 and neurological and orthopedic conditions.13,16 One study stated only that the participants were nursing home residents.18 Two studies included both subjects with neurological conditions and healthy subjects.6,29 Sample sizes varied widely (range, 6–150).
RELIABILITY OF UNIVERSAL GONIOMETER
One study was found, which concluded that intertester reliability for measuring internal and external rotation was excellent (0.90–0.94; Table 1).20
One study reported good to excellent intratester reliability for measurement of hip extension (0.70–0.96).21 Two studies reported weak to excellent intratester reliability for measurement of hip extension (0.09–0.92).6,26 Two studies found weak to good intertester reliability for measurement of hip extension (0.10–0.65).26,29 In contrast, another study found excellent intertester reliability for measurement of hip extension (0.92).25
A single study reported on intratester reliability for hip flexion and found weak to excellent reliability (0.52–0.99; Table 1).6
No study was found investigating measurement of active hip motion.
Three studies reported good to excellent intratester and intertester reliability (0.61–0.981) for measurements of hip extension, flexion, abduction, and lateral rotation among patients with neurological conditions.4,9,24 Two studies also found excellent intratester reliability for measurement of hip abduction (0.82–0.95) and hip extension (0.98) but weak intertester reliability for measurement of hip extension (0.24) and hip abduction (0.37–0.47) among the same patient group.18,23 Another study reported weak intertester reliability for measurement of hip extension (0.19–0.50).29 One study found inconsistent results and significant variation in intratester reliability within one session and between sessions for measurement of hip extension (0.17–0.91) and flexion (0.55–0.80; Table 1).6
No study was found investigating measurement of active knee motion.
Two studies reported excellent intratester reliability for measurement of knee flexion (0.96–0.99) and knee extension (0.83–0.97).15,27 One study reported good intratester reliability for measurement of knee flexion (0.65–0.72),28 whereas another study found weak to excellent intratester reliability for knee extension measurement (0.34–0.99).6 Other studies found good to excellent intertester reliability during measurement of flexion (0.88–0.99) and extension (0.64–0.71; Table 2).7,15,27 On the other hand, three studies found weak to good intertester reliability for measurement of knee extension (0.21–0.68) and flexion (0.44–0.59).27–29
A single study was found, which reported excellent intratester and intertester reliability of flexion and extension among patients with orthopedic conditions (0.89–0.99; Table 2).22
Intratester reliability was found to be excellent in four studies investigating measurements of knee flexion (0.99) and extension (0.81–0.98) among subjects with neurological and orthopedic conditions.4,9,13,18 However, one study reported weak to excellent intratester reliability for measurement of knee extension (0.57–0.92) among subjects with neurological conditions.6 Two studies reported weak intertester reliability for measurement of knee extension (0.2629 and 0.589) among subjects with neurological conditions. On the other hand, three studies reported good to excellent intertester reliability for measurement of knee extension (0.78–0.96; Table 2) among subjects with neurological and orthopedic conditions.5,13,18 One study reported excellent intertester reliability (0.90) for measuring knee flexion among patients with neurological and orthopedic conditions.1
No study was found to determine measurement of active ankle motion.
A single study was found, which reported good to excellent intratester and intertester reliability for dorsiflexion (0.63–0.99; Table 3).6
A single study reported weak to excellent intratester reliability (0.47–0.93) and weak intertester reliability (0.25–0.28) for the measurement of plantarflexion and dorsiflexion among patients with orthopedic conditions (Table 3).19
A single study examined measurement of dorsiflexion and plantarflexion among patients with diabetes and found excellent intratester reliability (0.89–0.96), whereas the intertester reliability varied between good to excellent (0.74–0.89).17 Five studies reported excellent intratester reliability (0.81–0.99) during measurement of dorsiflexion and plantarflexion among patients with neurological and orthopedic conditions.4,6,9,16,24 By contrast,two other studies reported weak to good intertester reliability (0.12–0.73) during measurement of dorsiflexion and plantarflexion among the same patient group,9,16 excluding two studies where excellent intertester reliability was found for measurements of plantarflexion and dorsiflexion (0.87–0.88).5,24
Several different designs of goniometers have been developed over the years including the UG, electrical goniometer (EG), and gravity-dependent goniometer (inclinometers).25,32,33 The UG is the most frequently used tool in the clinical environment. However, the disadvantage of using a UG is the requirement of using two hands to move the joint while simultaneously aligning the UG with bony landmarks, which may compromise reliability.16,34 New technologies are recently emerging for joint ROM measurements, such as dimensional and three-dimensional video recording systems.35,36
This review included 21 studies investigating intratester and intertester reliability of the UG in measuring active or passive ROM of lower-limb joints among patients or healthy subjects.
In general, reliability of the UG varied across different pathologies, proving to be most reliable among healthy subjects. A number of studies stated that the presence of spasticity is a major cause of error23,30,37,38 and concluded that care should be taken when using the measurements obtained using the UG for assisting in clinical judgment.30,37 However, Kilgour et al.6 compared measurement reliability of healthy subjects to those with spastic diplegia and found equal reliability.6 This study concluded that a major cause of error was in defining the end range of the joint ROM rather than the presence of spasticity. Furthermore, Lee et al.29 also compared measurement reliability of healthy subjects to those with cerebral palsy (CP) and found higher reliability among subjects with CP. Elveru et al.16 reported a higher intertester reliability for ankle plantarflexion ROM in patients with general orthopedic conditions in comparison with patients with neurological conditions.
Some studies included more than one form of pathology and grouped results without reporting on each pathology individually.15,18,19,22 Three studies included more than one form of CP and did not report on each group separately, hence reducing the ability to interpret results.5,23,29
Watkins et al.13 investigated intratester and intertester reliability of knee joint ROM among patients with different pathologies with knee joint problems and reported excellent reliability (Table 2). A posterior analysis was performed in the study to determine the effect of different pathologies on the reliability. Overall, pathology did not have an effect on the intratester and intertester reliability. However, intertester reliability for knee extension was found to be weak among persons with transtibial amputation, which may be explained due to short distal limb segment causing difficulties in aligning the UG.
Passive ROM is the motion mostly measured in clinical environment, and only 3 studies included in this review reporting on active motion. Two studies reported excellent intratester and intertester reliability for measuring hip and knee joint active ROM (Tables 1, 2).20,22 Another study reported weak to excellent intratester reliability and weak intertester reliability for measuring active ankle ROM (Table 3).19 The limited number of studies found measuring active motion compromised the ability to make comparisons with measuring passive ROM. However, one study stated that the low intertester reliability could be explained due in part to the difference in the force applied by therapists during assessments of passive motion, causing different angles to be obtained during each session.9
It was noted that reliability varied across the joints measured due to the different joint characteristics and ease of identifying bony landmarks. Overall, reliability varied from weak to excellent across the hip, knee, and ankle joint. Despite the fact that the knee joint is a polycentric joint where the center of rotation changes with motion, it was found to be a reliable joint to measure, and this is supported with the high ICC values found (Table 2).7,13,15,22 Measurement of knee flexion seems more reliable than measurement of knee extension ROM (Table 2).13,15,22 Similar results were found for measurement of hip joint ROM, as some studies reported excellent intratester and intertester reliability for the measurement of hip extension, abduction, and external rotation (Table 1).4,9,18,23–25 This suggests that although joint characteristics are a factor affecting reliability, the length of lever arms may have more effect. Aligning the arms of the UG to follow the long bones in the thigh and calf and the mid lateral trunk may assist knee and hip joint ROM measurements, making this more reliable. Excellent reliability was also reported for measuring the ankle joint ROM despite the short lever arm of the foot. Furthermore, it has been reported that even complex motions can be measured reliably when strict standard position is applied.39,40
Most studies provided the testers with a standard measurement procedure and prior training to minimize associated error. Rothstein et al.15 deliberately did not standardize the measurement procedure (measuring technique and patient's position) to mimic the clinical setting and stated that “measurement technique will often vary between the therapist, partially because of their training and preferences and partially because of adaptation, such as positioning, which is necessary with different patients.”(p1611) The study reported high intratester reliability during measurement of passive knee flexion and extension ROM and high intertester for knee flexion ROM but lower intertester reliability for knee extension ROM among patients (Table 2).15 To examine the effect of the different patient positions used in the study, a posterior analysis of the results was carried out and an increase in intertester reliability for knee extension was reported (from 0.20–0.69 to 0.74–0.84) when the same position was used. It was suggested that using different patient positions while measuring causes variability due to the biarticular muscles (hamstrings) affecting the knee extension.15 The hamstrings muscles cross both hip and knee joint, limiting knee extension ROM when the hip is flexed; hence, variation in position of the hip joint during measuring knee joint extension can cause differences in the measurements obtained. Subject position varied across a number of studies. The positions used to measure hip joint ROM were Thomas test, modified Thomas test, prone hip extension test, supine position with knee maintained in different degrees of flexion, prone position, and seated position. Kilgour et al.6 reported higher intratester ICC values for the Staheli test (0.78–0.91) in comparison to the Thomas test (0.17–0.66) in subjects with CP. Furthermore, intratester ICC values for the prone hip extension test (0.80–0.92) were found to be higher than intratester ICC values for the Thomas test (0.09–0.91) among healthy subjects in the previous study. A further study found weak intertester reliability when using the Thomas test (0.58).5 In contrast, Lee et al.29 reported higher ICC values for the Thomas test (0.20–0.50) in comparison to prone hip extension test (0.10–0.19) among subjects with CP and healthy subjects. Van Dillen et al.21 compared 4 positions for measuring hip extension, which included femur maintained in 0° abduction with knee maintained in 80° flexion, femur maintained in 0° of abduction with knee fully extended, femur fully abducted with knee maintained in 80° of flexion and femur in full abduction, and knee fully extended. In this study, the higher intratester reliability was achieved for the position where the femur was fully abducted and knee fully extended (0.96). Simoneau et al.20 measured hip external and internal rotation using prone and seated position and concluded higher ICC values were achieved for internal rotation (0.94) and external rotation (0.93) in the prone position. The study recommended documentation of the position of the hip to allow repeated reliable measurements. It has been reported that proper aligning of the UG when measuring using the Thomas test or prone hip extension test can be difficult because one hand is used to ensure the lumbar spine is flat and the other hand is used to align the UG while maintaining the position of both arms of the UG.5 For knee ROM measurements, the following positions were used: popliteal angle and supine position with hip extended. Kilgour et al.6 compared measuring knee extension with the hip in neutral and in 90° flexion and found higher ICC values with the hip in a neutral position in subjects with CP and healthy subjects. On the other hand, Cadenhead et al.4 found equal reliability when measuring knee extension while maintaining the hip in neutral or 90° flexion. For ankle joint ROM measurements, the following positions were used: supine position with knee extended, supine position with knee flexed, and prone position. A study found equal intratester reliability when measuring ankle dorsiflexion with knee extended and knee flexed.6 Diamond et al.17 measured ankle dorsiflexion in prone position and reported good to excellent intratester and intertester reliability.
Another source of error could be due to the discrepancies in identification of bony landmarks and goniometric alignment between the testers. Peeler and Anderson28 carried out a pilot testing with 3 testers and found that differences were reported between testers when identifying the lateral epicondyle of femur (used to align the axis of the UG), especially in patients with pathological changes at the knee.15 In addition, they reported that difficulties were found in maintaining the position of the axis of the UG when trying to align the two arms. In addition, Watkins et al.13 followed nonstandard measuring procedure and reported excellent intratester and intertester reliability for measurements of knee flexion and extension in patients with knee pathologies. A posterior analysis of the results showed that nonstandardization of the measurement procedure contributed slightly to measurement error but still suggested that standard procedures be applied to minimize this error (when the same patient position was used, ICC for flexion increased by 0.02 and for extension by 0.01).13 A further study found weak intertester reliability when measuring active ankle ROM in patients when the position was not standardized, suggesting that a standard protocol should be established and followed.19 The weak intertester reliability reported in this study may be explained due to the variation in the UG alignment using bony landmarks. In measuring the ankle joint, the fixed arm is aligned over the long axis of fibula; however, the moveable arm could be aligned with the heel, fifth metatarsal, or plantar surface of the foot causing variation in measurements among testers.19 In addition, the variation found in the study by Youdas et al.19 may be explained due to the effect of the gastrocnemius muscle, which crosses the knee and ankle joint, limiting the available ankle dorsiflexion ROM when the knee is extended. Different knee joint positions used in the previous study may have caused different ankle dorsiflexion ROM to be recorded, leading to variation in results (wide range of intratester and intertester ICC reported). In contrast, another study stated that lack of standardization was not a significant factor for difference among the testers (intertester) during measurements of passive ankle plantarflexion ROM.16 However, the opposite was reported for ankle dorsiflexion ROM (ICC increased by 0.09 when using different position and decreased by 0.10 when using same position) but still rated as weak intertester reliability (Table 3).16 Furthermore, it was stated that involving two testers in the measurement procedure may increase the reliability of the UG among CP patients as one tester stabilizes the limb and the second tester takes the measurements.5
Generally, it was found from the studies included in this review that intratester reliability was higher than intertester reliability (Tables 1–3).9,15–19,23,27,29 One study suggested that averaging two measurements each session increases the reliability of the measurements obtained,19 agreeing with the findings of low.41 However, a study by Rothstein et al.15 found that no greater reliability is obtained when mean of measurements is used, suggesting that reliability can be achieved by taking a single measurement in clinical settings. In addition, a posterior analysis of the results by Elveru et al.16 suggested that no increase in reliability was achieved when using the mean of two measurements, agreeing with the finding of Boone et al.42 The results of Kilgour et al.6 showed no increase in reliability when averaging two measurements but stated that “taking two duplicate measures in clinical practice could help therapists to identify measurements within on session that might need to be repeated.”(p399)
The ability to make direct comparison between the studies was compromised due to the differences in methodology adopted in the studies, such as the level of experience of the testers, number of sessions, and time between the sessions.
Most studies included testers who were physical therapists with experience level ranging from 115,23 to 306 years. McWhirk and Glanzman5 included two therapists with different levels of experience (1 and >10 years' experience) to investigate the intertester reliability in subjects with CP. They found good to excellent reliability for all the motions measured excluding hip extension ROM (0.58; Tables 1–3). Elveru et al.16 preformed a posterior analysis of the results to investigate the effect of experience on reliability and reported an increase in intratester ICC from 0.90 to 0.91 for ankle dorsiflexion and from 0.86 to 0.92 for ankle plantarflexion, and an increase in intertester ICC from 0.50 to 0.54 for ankle dorsiflexion and a decrease from 0.72 to 0.70 for ankle plantarflexion when more experienced testers took the measurements. Although an increase in ICC was reported, this increase did not affect the overall rating of the ICC values. However, limited information about the tester experience was provided. The rest of studies did not provide additional results to show the effect of the testers experience on the reliability obtained.
The number of testing sessions and the period between each session varied across the studies. Most studies used a test-retest design to calculate intratester reliability of measurements taken by different testers on the same day.4,5,7,13,15–22,25,29 Kilgour et al.6 investigated intratester reliability within and between sessions (1 week apart) for passive ROM of hip, knee, and ankle joint among subjects with CP and healthy subjects. In this study, all intrasessional ICC values were found to be higher than intersessional ICC values (Tables 1–3). Wakefield et al.26 also reported weak intratester intersessional (between sessions) ICC values for hip extension among healthy subjects (Table 2). In contrast, Mutlu et al.24 and Herrero et al.23 reported high intratester intersessional ICC values for all the motions measured among subjects with CP (Tables 1, 3). Pandya et al.9 reported excellent intratester intersessional ICC values for all measurements obtained among subjects with Duchenne muscular dystrophy, and Peeler and Anderson28 reported similar results among healthy subjects (Tables 1–3).
It is important to consider measurement reliability in the clinical context. It is reported that an error of ±5° in measurement may be clinically acceptable.43 Hence, clinicians should be cautious when interpreting results of reliability studies and must select studies appropriate to pathology. Although Mutlu et al.24 reported good to excellent intertester reliability, a variation of 0° to 28° was found in intertester measurements. In addition, another study reported a variation of 15° to 20° in the measurements between sessions.6 The clinical effect of such findings must be considered, especially when using measurements to determine treatment effect.
This review aimed to investigate the intratester and intertester reliability of the most commonly used measurement tool, the UG, and to examine how different factors can influence reliability. Twenty-one studies were included, which investigated the reliability of measuring hip, knee, and ankle joint ROM. This literature review highlights variation in the methodology used, which reduced the ability to compare studies directly because the number of testers, experience level, number of sessions, time between the sessions, and subject position varied across the studies. Most studies indicated that the UG reliability was best when used to measure ROM in healthy subjects and that reliability may be reduced in the presence of different pathologies. Passive ROM is the motion mostly measured in the clinical environment, and hence a larger number of studies have examined the reliability of measurement of passive motion rather than active motion. The limited number of studies measuring active motion compromised the ability to make comparisons with measurement of passive ROM. It was stated that the low intertester reliability could be explained due in part to the difference in the force applied by therapists during assessments of passive motion, causing different angles to be obtained during each session. Generally, it was found that intratester reliability was higher than intertester reliability. Reliability varied from weak to excellent across the hip, knee, and ankle joints due to the different joint characteristics and ease of identifying bony landmarks. It has been reported that even complex motions can be measured reliably when a strict standard position is applied. Standardization of the measurement procedure and prior training were found to increase measurement reliability, and one study suggested that involvement of more than one tester in the measurement procedure may have a beneficial effect on reliability. Further research is required to investigate the reliability of the UG and the possibility of using protocols and technology to increase reliability when measuring joint ROM.
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