Netherlands Institute of Primary Health Care (NIVEL), Utrecht,
1 Institute for Research in Extramural Medicine, Vrije Universiteit, Amsterdam,
2 Netherlands Institute for Allied Health Professions (NPI), Amersfoort, The Netherlands and Faculty of Medicine and Pharmacology, Free University of Brussels, Brussels, Belgium and
3 Department of Rheumatology, Utrecht University Medical Centre, Utrecht, The Netherlands
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Abstract |
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Methods. Data on 198 patients with OA of the knee or hip were used. The ROM was assessed bilaterally for the hip and knee, using a goniometer. Disability was assessed using a self-reporting method (questionnaire) and an observational method. Correlation and factor analysis were used to establish the inter-relationships between the ROMs of joint actions. Correlation and multiple regression analyses were carried out to establish the relationships between ROM and disability.
Results. Close inter-relationships were found between the ROMs of the same joint action of the lateral and contralateral joints; inter-relationships between ROMs of different joint actions were substantially weaker. Low ROMs were associated with high levels of disability, both self-reported and observed. Some 25% of the variation in disability levels could be accounted for by differences in ROM. In both knee and hip OA patients, flexion of the knee and extension and external rotation of the hip were found to be most closely associated with disability.
Conclusion. Restricted joint mobility, especially in flexion of the knee and extension and external rotation of the hip, appears to be an important determinant of disability in patients with OA.
KEY WORDS: Osteoarthritis, Range of motion, Disability
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Introduction |
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Relationships have been reported between the range of joint motion in general and disability. Dunlop et al. [7] identified joint impairment as a predictor of disability. In their study, the presence of an impaired ROM was one of the factors defining joint impairment, but other factors, such as tenderness, swelling and pain during motion, were also used in the assessment of joint impairment. Thus, their study did not identify a separate association between joint mobility and disability. In a study among elderly Swedish people, strong correlations were found between the ROMs of the knee and hip joints and disability [8]. In another population study, Odding et al. [9] found that restricted flexion of the hips and restricted flexion of the knees were strong risk factors for locomotor disability (disability in activities primarily involving the lower extremities, such as walking, climbing stairs, and rising from and sitting down in a chair). Recently, Escalante et al. [10] reported that impaired hip flexion was associated with a decrease in walking velocity in a population of elderly persons.
The existence of this relationship has also been reported in patients with OA. In a review of previous studies, Dekker et al. [2] identified impaired joint mobility in general as a factor in the development of disability in patients with OA. However, to our knowledge, no further research on this topic has been published in recent years. The role of physical functioning as a determinant of disability in OA has been investigated widely, but research has focused primarily on the effect of decreased muscle strength on disability in OA [4, 5, 1113]. The relationship between joint mobility and disability in OA has not been established in more detail than in the global statement of Dekker et al. [2]. The effect of restricted mobility of specific joint actions on disability has not been established in patients with OA. Establishing these relationships in detail could provide essential information for both the assessment and the management of disability in patients with OA.
The overall goal of the present study was to further establish the relationship between ROM and disability in patients with OA of the knee or hip. To this aim, two related issues were addressed. First, the inter-relationships between the ROMs of all joint actions of the knees and hips were studied. Before studying the role of ROM as a determinant of disability, it is of vital importance to have insight into the nature of ROM in OA. Can ROM be regarded a unidimensional trait of an OA patient (i.e. are the ROMs of all joint actions closely inter-related and can they be regarded as representations of one traita patient's overall sinuosity)? Or must the ROMs of separate joint actions be treated as separate entities, each with its own specific effect on a patient's level of physical ability? Secondly, after the best level of aggregation for ROM data had been established, we studied the relationship between ROM and disability in OA.
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Methods |
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Range of motion
The assisted active ROM was measured bilaterally for the hip and knee, using a goniometer. ROM measurements were recorded in degrees. Measurements were taken according to Norkin and White [17]. These measurements were taken for all possible actions of the joint, i.e. flexion, extension, internal and external rotation, abduction and adduction of the hip, and flexion and extension of the knee. For each action, the protocol provided starting positions for both patient and therapist, reference points for the pivot and distal points of the goniometer, and a horizontal position (defining positive and negative values for ROM). For patients who were unable to adopt a prescribed starting position, the protocol provided an alternative starting position. By supplying a protocol for starting positions for the patient and therapist and the positioning of the goniometer, the reliability of the ROM measurements was increased [18]. The full protocol for taking ROM measurements can be obtained via the internet, at http://www.nivel.nl/english/range-of-motion/protocol- ROM.html. The tests were carried out by two experienced physical therapists. Before taking the measurements used for the present study, the inter-rater reliability was established using 10 healthy subjects and 10 patients with OA. The inter-rater reliability was satisfactory for all joint actions (Pearson's R > 0.75 for all actions).
Disability
Two methods were used for the assessment of disability: one observational method and one questionnaire.
Observed disability was determined by watching videotaped performances of patients in a series of standardized tasks [19]. These standardized tasks included walking, sitting down in a chair, reclining onto a bed and bending over to pick up a weight from the floor. Trained observers scored the performance of the patients. The observers scored five items: three movement times (time taken to walk 5 m, stand-to-sit time and stand-to-recline time) and two measures of the quality of the performance (level of guarding and level of rigidity). Based on these five items, an overall score for observed disability was calculated [19]. A higher overall score indicated a higher level of disability. This overall score has been shown to be internally consistent and valid [19].
In addition to observed disability, self-reported disability was assessed using the mobility subscale of the Influence of Rheumatic Disease on General Health and Lifestyle (IRGL) questionnaire. The IRGL is a Dutch adaptation of the Arthritis Impact Measurement Scales [20, 21]. This IRGL subscale has seven items. Two items are general statements concerning disability in mobility and the remaining five address disability in climbing stairs, riding a bicycle and walking. The IRGL is a positive questionnaire, i.e. it measures ability rather than disability. To facilitate interpretation, scores on this test were reversed to obtain a disability score. After reversal, the scores for this test ranged from -28 (minimal disability) to -7 (maximal disability).
Statistical analyses
To establish the inter-relationships of the ROM scores of the joint actions, Pearson correlation coefficients were computed and factor analysis was performed. Both types of analysis assess the associations between items (in this case, the ROM of joint actions), but correlation coefficients provide information only for pairs of items whereas with factor analysis it is possible to assess the inter-relationships within the complete pool of items. The number of factors resulting from the factor analysis provides information about the dimensionality of ROM. If the analysis produces one factor, containing all ROM items, joint ROM can be regarded as a unidimensional trait of the patient (i.e. the ROMs of different joint actions are all representations of the same traitthe patient's sinuosity). If more factors are identified, effectively isolating subgroups of closely associated items, joint ROM cannot be regarded as a trait of the patient, but a trait at a lower level (e.g. of the joint or the joint action). In the analysis, factors are identified if they can account for a significant amount of variance within the item pool (represented by an eigenvalue >1).
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Results |
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Inter-relationships of joint actions
The Pearson correlation coefficients between the ROM values of all joint actions of the knees and hips are presented in Table 2. The highest correlations were found between the identical actions of the lateral and contralateral joints (e.g. flexion of the left hip and flexion of the right hip); these correlations ranged from 0.35 to 0.82. Especially for the joint actions of the hip in the transverse and sagittal planes (flexion, extension and internal and external rotation), these correlations were high, ranging from 0.62 to 0.82. The correlations among other joint actions (i.e. actions other than identical actions of the lateral and contralateral joints) were substantially lower, ranging from -0.16 to 0.44.
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Range of joint motion and disability
Pearson correlation coefficients between the ROMs of joint actions on the one hand and disability on the other hand are presented in Table 4. Generally, there was a negative relationship between ROM and disability, i.e. a decreased ROM was associated with an increase in disability. However, not all joint actions seemed to be related to the level of disability in these patients. Extension, abduction and external rotation of the hip and flexion of the knee were associated primarily with disability (both self-reported and observed) in both patients with hip OA and patients with knee OA. To a lesser degree, significant relationships were also found between the ROM of flexion of the hip and disability.
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To test whether the presence of flexion contractures could be responsible for the relationship between joint ROM and disability, the regression analyses were also repeated with two dichotomous (present/absent) variables for flexion contracture of the knee or hip included as potential independent variables. However, the inclusion of flexion contracture as a potential determinant of disability did not change the outcome of these analyses; the results were equivalent to those presented in Tables 5 and 6
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Discussion |
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The inter-relationships between the ROMs of different joint actions were assessed using correlation and factor analyses. The most important finding was the clear inter-relationship found for the same joint action of the lateral and contralateral joints. High correlations between identical actions of the lateral and contralateral joints have also been reported by Escalante et al. [10]. In the factor analysis, the six different joint actions of the hip were clustered into four factors. Extension and abduction loaded on the same factor, while flexion and internal rotation loaded on another factor. The other two factors found for hip ROM were both loaded by a single joint action of the hip. The clustering of two different joint actions into one factor may be explained by the dependence of both joint actions on the same muscles. A number of muscles are responsible for more than one joint action of the hip, mainly combining flexion or extension with medial or lateral rotation [22].
No major differences were found between patients with hip and knee OA with regard to the relationships of joint ROM with disability. The results were similar for the two subgroups of patients. Extension and external rotation of the hip showed significant relationships with disability in patients with knee OA. Likewise, flexion of the knee was associated with disability in hip OA patients. Although the study population included some patients (10 in total) with both types of OA (who were therefore included in both subgroups), these patients were not responsible for the existence of these relationships in this population. The results of the subgroup analyses did not change significantly when patients with both types of OA were excluded.
Some issues need to be addressed concerning the methods used in this study and their effect on the results presented here. Joint ROM can depend on factors other than articular deformation. Certain motions may be too painful for the patient to complete, or the patient may lack the muscle strength to maintain the joint action. This results in impaired ROM without a clear articular cause for this impairment. In the present study, the effect of muscle strength on ROM was minimized by determining the assisted active ROM. This means that the therapist provided support against the pull of gravity but no support for the completion of the joint action. The patient had to carry out the motion by himself, using muscle strength to increase the angle, but did not have to use his muscle strength to keep his limb in position. Of course this minimizes, but does not eliminate, the effect of muscle strength on ROM. Neither does it eliminate the influence of pain during motion on ROM, and it does not take the clinical status of the joint (whether or not it is diagnosed as having OA) into account. However, the aim of the present study was to reveal the role of ROM as a determinant of functional disability. Joint ROM has its own determinants, but whether an impaired ROM is caused by pain during motion, insufficient muscle strength or intra- and periarticular deformation due to OA is a question beyond the scope of this study. More in-depth research needs to be carried out to provide insight into this complex matter.
To our knowledge, other research on the topic of joint mobility, especially the range of joint motion of specific joint actions in patients with OA, and disability has been scarce. In a population survey, Odding et al. [9] found that restricted ROM of a number of joint actions was associated with the presence of locomotor disability. The strongest relationships were found for flexion of the knee and flexion of the hip. Significant, but weaker, relationships with disability were also found for internal and external rotation of the hip. This is partly consistent with the findings of the present study. Both studies found a relationship between the presence of disability and the restricted range of joint motion in the sagittal (flexion of the knee and flexion or extension of the hip) and transverse planes (internal and external rotation of the hip). One major difference, however, is that in the present study extension of the hip was found to be closely associated with disability, whereas Odding et al. [9], and also Escalante et al. [10], identified impaired flexion of the hip as a strong risk factor for disability. This may be attributable to differences between the studies in the population under survey: for the present study the data were from patients with OA of the hip or knee, whereas the other two studies were surveys of a general population of elderly people. It is possible that, in patients with OA, the relationship between joint ROM and disability differs from that in the general population, perhaps because of the presence of flexion contractures in patients with OA. Another possibility is that differences between the studies in the protocol for taking ROM measurements (in defining the horizontal, starting positions, etc) have led to different results.
We conclude that there is a clear relationship between joint ROM and disability in patients with OA of the knee or hip. However, the relationship does not apply to all actions of the knee or hip joints. Flexion of the knee and extension and external rotation of the hip were found to be most strongly associated with disability. Restricted joint ROM appears to be an important risk factor for the occurrence of locomotor disability in patients with OA.
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Notes |
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References |
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