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1 School of Physiotherapy, Curtin University of Technology, Perth, Western Australia.
2 MGH Institute of Health Professions, Boston, Massachusetts.
3 The Centre for Musculoskeletal Studies, Department of Surgery, University of Western Australia, Perth, Western Australia.
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Abstract |
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Method. Fifty-nine community dwelling subjects, 30 young (mean age 21.7 years) and 29 older (mean age 75 years), were recruited to determine normal reference ranges for the effect of age on hip JPS. Active and passive repositioning tasks were performed in inner and outer ranges of the hip abduction plane of movement. An electromagnetic tracking system was used to obtain accurate error measurements of the angular displacement.
Results. Results indicated no difference in hip JPS between the young and older subjects (
). However, it was found that for both age groups, accurate reproduction of position at the hip joint occurred in the inner range (
). For both groups, active repositioning was more accurate than passive (
).
Conclusions. In this study, no difference in hip JPS was found between young and older subjects. Accuracy was greater in the inner range, with active repositioning demonstrating higher precision compared to passive repositioning of the limb.
Few studies have examined the JPS of the hip in relation to age. Most of those researchers examining the proprioceptive acuity of the hip joint have studied cohorts following surgical hip replacement. The consensus was that in these groups, proprioceptive acuity was not significantly altered (3–6,8).
Studies of JPS in the ankle and knee joints have shown a decline in accuracy with aging (9–11). To date, no studies have been found on the effect of age on hip JPS. Therefore, the objectives of this study were to determine (a) if hip JPS deteriorates with age, (b) if hip JPS relates to the available joint range of motion (ROM), (c) if there was a difference between passive and active JPS, and (d) if hip JPS acuity was range dependent.
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METHOD |
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Prior to testing, all subjects completed a demographic survey including questions related to the type and level/intensity/duration of recreational physical activities undertaken each week. The level of physical activity was derived from the self-report data (from 0–1 = low-intensity physical activity [1 hour/week] up to 5 = high-intensity physical activity [20 hours/week]). The older subjects also completed the Functional Status Index to determine the level of independence in the community (12).
Instrumentation
The 3Space Fastrak (Polhemus Navigation Sciences Division, Vermont) motion analysis system was used to measure angular displacement. The system consisted of an electronic unit, transmitter/source unit, and three motion sensors. The source unit generated an electromagnetic field that determined the location and orientation of the sensors in space relative to the source unit. Sensors were placed over the center of the sacral crest and over the right and left lateral femoral epicondyles. The transmitter was positioned within a 1-meter arc of all three sensors.
Subjects were positioned supine on a wooden plinth (to minimize interference with the electromagnetic 3Space Fastrak system), with two freely moving lower limb supports (Figure 1). Each limb support could rotate on a proximal axis, allowing free movement of either hip in an abduction/adduction arc of movement, while the other hip remained constrained. The hip joint was positioned above the axis of rotation of the lever arm, and the lower limb was positioned at zero/neutral according to a goniometer affixed to the rotation axis of the tested limb.
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Measurement Procedure/Protocol
The active abduction and adduction ROM was measured over three trials using 3Space Fastrak system. The average was recorded and used for each subject's active repositioning tasks.
The study sought to determine the influence of muscle proprioceptors on JPS. During pilot testing, we discovered that if the subject performed too many repositioning tasks, their performance deteriorated. Hence, for the passive reproduction tasks, where the tension of the muscle was not a critical component, one 20° range of motion was used, ±10°, either side of the neutral (0°) position.
Two ranges of movement through 20° were used for the active repositioning tasks to ascertain if there was a difference in the JPS when the muscles performed in different ranges. The testing ROM related to the ROM of the abductor muscles, not the ROM of the joint.
As JPS at the end of range for both the muscle and joint tends to rely more on the joint mechanoreceptors, the start and target positions were not at the extremes of (joint) range and were related to the individual's joint ROM (14) (Figure 2). The different testing conditions (side, action, and range) were presented in a balanced randomized order.
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The active reproduction task was performed similarly, the subject being instructed to abduct the hip slowly until the investigator indicated "stop" as a target position. The subject then returned to the starting position and actively attempted to match the target position.
Three trials were performed for each hip joint for all JPS tasks. Both passive and active target and reproduced positions were acquired in Labview 4.1 (National Instruments, Austin, TX), and absolute error scores were calculated. The average of these scores formed the passive and active error scores for each subject.
Once the ROM and JPS testing was complete, the older subjects walked 20 m at their own fast pace. The time taken to walk the central 10 m was recorded.
Statistical Analysis
SPSS 10.0 (SPSS, Inc., Chicago, IL) was utilized for all analyses. Descriptive statistics were obtained to determine the population variance. A three-way multivariate analysis of variance (MANOVA) was performed to examine the differences in ROM scores for abduction/adduction and the total ROM between the groups, gender and sides.
A two-way analysis of variance (ANOVA) was conducted to examine the difference in JPS error scores for the three repositioning tasks for gender and the sides. Repeated measures ANOVA and contrasts were performed to view significant differences in JPS error scores between the age groups, passive and active tasks, and active tasks in the inner and outer abduction ranges.
In order to examine the effect of ROM, physical activity levels, and walking velocity on JPS, Pearson's correlation coefficients (r) were calculated. The criterion of significant differences was accepted at a level of 
.
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RESULTS |
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The descriptive statistics for range of joint motion are presented in Table 1. A 2 (group) x 2 (side) x 2 (gender) MANOVA on abduction and adduction ROM tasks revealed a significant main effect for age group (
), with no significant interactions between the right and left sides and gender. Univariate tests demonstrated a significant difference in the abduction ROM (
), with the young group having greater range than the older group. However, there was no difference in the adduction range (
) between the 2 groups.
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). Univariate analyses revealed a significant interaction for the active outer task (
) but not for the two other tasks. For the active outer task, females showed a greater error than the males on the right side (
), but not on the left side (
). Considering the size of the difference (.8°) and the fact that only one of the three tasks showed a significant effect, it was decided to treat the males and females as one group for the remaining analyses. Side data were grouped since there was no significant difference between the right and left.
A 2 (group) x 3 (JPS task) MANOVA showed no significant interactions but a significant difference between the mean error scores for the three tasks (
). Contrasts indicated the active repositioning task was more accurate than the passive (
). The active outer and inner range scores were different (
); the repositioning task performed in the inner range of the hip abductor muscles was more accurate than in the outer range, as can be seen by the mean error scores (Figure 3).
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DISCUSSION |
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Relationship Between Age and ROM
James and Parker (16) reported a decline in abduction ROM in subjects over 70 years of age, with the greatest decline occurring in the ninth decade. They found that the adduction ROM did not change with age. The results from the present study confirm these findings, with a significant decrease in abduction range between the young and older groups and no significant changes for adduction.
Relationship Between JPS and Age
JPS of the knee has consistently been demonstrated to decline with age (9,11,17,18). In contrast, a key finding from this study is that there were no significant differences in hip JPS between the young and older subjects for either passive or active repositioning tasks. It is difficult to compare the results from this study with the relevant literature, as there are no normative, age-related data on JPS of the hip joint. Further, there is great variability in methodologies employed for studies of the knee, which makes generalizations to this assessment of the hip inappropriate. The older subjects in this study were active, participating in an average of 10 hours of exercise each week. Petrella and colleagues (18) examined the effect of activity on knee proprioception in active and sedentary older groups and found that the active group members were more accurate in detecting joint position. People who exercise have greater strength and faster reaction times (19). The reason why this study was unable to demonstrate a difference between the two age groups may have been that the older group were active. Half of the older subjects played lawn bowls on a regular basis. Lawn bowls requires considerable control of balance and movement, with the hip working in a wide range of positions, especially those challenging the hip abductor mechanism during a tandem lunge position characteristic of the bowl delivery. Exercise appears to influence proprioception as well as the ROM and strength (18). It is possible, therefore, that activity undertaken by this elderly population maintained or enhanced their hip proprioceptive acuity (20). The mechanisms that underlie the maintenance of hip proprioception in the older population, as demonstrated in this study, warrant further examination.
Relationship Between Passive and Active Hip JPS
Active reproduction of joint position was found to be more accurate than passive reproduction. An early study by Paillard and Brouchon (21) found that movement precision was significantly improved with active repositioning. In the current study, in both the active JPS tasks, the hip abductor muscles contracted concentrically to reach the target position. This active contraction requires contribution of the muscle spindles in the hip abductors and may provide more afferent feedback regarding position than do the passive tasks (14,20). In this study, active JPS was measured in the inner and outer range of the hip abductors. As the muscles contracted to a shorter length in the active inner task, greater feedback from muscle afferents regarding position would be expected compared with the active outer task. This may explain the finding of increased JPS accuracy in the inner range of the hip abductor muscles.
Relationship Between JPS and Joint ROM
Elderly subjects with a greater range of abduction motion showed a decreased proprioceptive acuity. In a study by Barrack and colleagues (1984), ballet dancers who had extreme range of joint flexibility performed knee JPS tasks less accurately than the control group. It was suggested that there could well be an upper limit at which too much flexibility results in reduced proprioception, possibly due to the laxity of the ligaments. The negative relationship could also be explained by the relationship of muscle length to available joint ROM. Following testing, several subjects reported using muscle tension to determine the location of the target angle. If there is greater flexibility, muscle tone could be decreased, which would minimize the possibility of using muscle tension cues, resulting in a greater proprioceptive error.
In conclusion, hip JPS in the abduction plane of movement does not diminish in older active subjects, relative to available range. A decrease in abduction ROM with age was confirmed. Hip JPS is more accurate when performed actively than passively, especially when performed in the inner range of the hip abductor muscles.
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Acknowledgments |
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Address correspondence to Christine M. Pickard, School of Physiotherapy, Curtin University of Technology, Kent Street, Bentley, Western Australia, 6102. E-mail: c.pickard{at}curtin.edu.au
Received July 31, 2002
Accepted October 28, 2002
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References |
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