- Top of page
- SUBJECTS AND METHODS
- AUTHOR CONTRIBUTIONS
Foot pain has been defined as an unpleasant sensory and emotional experience preceding perceived damage to the area distal to the tibia and fibula and has been attributed to direct trauma, musculoskeletal overload, infection, or systematic or proximal pathology (1). Foot pain has been found to be present in up to 60% of the older population (2–9) with the prevalence of foot/ankle pain increasing with age, reaching a peak in those age >75 years (8).
Factors associated with foot pain include being female (9–11), obesity (9–12), pes planus foot type (4, 6, 13, 14), wearing ill-fitting shoes (15, 16), sensory impairment (15), pain in the back, hips, knees, and hands or wrists (4, 10–12, 14), and depression (4, 11). For those who experience foot pain, it has been most frequently reported to occur when walking (7), with studies reporting that up to 80% of people with foot pain have walking difficulty (6, 14). Furthermore, older adults with foot pain have a higher prevalence of reported inability to carry out activities of daily living than those without foot pain (2, 6, 13) and hence, have reduced health-related quality of life (HRQOL) (12).
Reduced functional capacity can be observed in the gait characteristics of individuals with foot pain, whereby they typically reduce their walking speed (17, 18) and take more steps to complete a walking task (6) than those without foot pain. Of greater consequence, our recent research identified that community-dwelling older adults with foot pain are at a greater risk of falling (19), substantiating foot pain as a fall risk factor as previously reported in older disabled women (20) and older retirement village residents (21). Despite the growing evidence that foot pain is a fall risk factor for older people, the mechanisms behind the association between foot pain and falls are poorly understood.
One of the major barriers to investigating factors associated with foot pain has been the lack of validated foot-specific outcome measures to assess self-reported foot pain and related functional impairment. The Manchester Foot Pain and Disability Index (MFPDI) has been validated as a suitable instrument for assessing the impact of painful foot conditions in both clinical and community populations (22) and, as such, is becoming a widely used tool for epidemiologic studies (4, 10, 14, 23). However, classifying individuals with disabling foot pain using the criterion of a minimum of 1 item experienced only on “some days” has the potential to include people with relatively mild symptoms (14) and may not be able to discriminate beyond the presence of foot pain in older people where foot pain is highly prevalent (24) and symptoms vary considerably. This consideration has recently prompted the suggestion of using an alternate definition of disabling foot pain, where at least 1 item of the MFPDI is scored as “most/every day(s)” (24).
To date, no study has investigated whether the 2 above definitions of disabling foot pain are associated with objective measures of foot function and functional ability. Therefore, the primary objective of this study was to determine whether disabling foot pain, using 2 different definitions, was associated with foot function characteristics, functional ability, and HRQOL in older adults.
Significance & Innovations
Older people with disabling foot pain exhibit functional impairment and reduced health-related quality of life.
Disabling foot pain is associated with impaired foot function, in particular foot and ankle muscle strength.
A conservative definition of foot pain better discriminates those with impaired foot function.
- Top of page
- SUBJECTS AND METHODS
- AUTHOR CONTRIBUTIONS
Foot pain was present in 49.7% of participants using Definition A (at least 1 item scored as on some days or on most/every day[s]) and 26% of participants using Definition B (at least 1 item scored as on most/every day[s]). Regardless of the definition, women had a significantly higher prevalence of foot pain than men, and participants with foot pain had a significantly higher BMI (Table 1), justifying the inclusion of sex and BMI as covariates in further analyses. Using Definition A, obese participants (BMI >30 kg/m2) were more likely to report foot pain (63%) than those who were overweight (BMI ≥25 and ≤30 kg/m2, 43%) or in the normal weight range (BMI <25 kg/m2, 43%; P < 0.01). Among those with foot pain (Definition A), 68% had visited a health professional about their feet. Those indicating disabling foot pain using Definition B were more likely to have visited a health professional about their feet (79%).
Table 1. Descriptive characteristics, foot function, and postural sway for foot pain and no pain groups*
|Variable||Definition A||Definition B|
|No foot pain (n = 157)||Foot pain (n = 155)||No foot pain (n = 231)||Foot pain (n = 81)|
|Descriptive|| || || || |
| Women, no. (%)||63 (40)||91 (59)†||106 (46)||48 (59)‡|
| Age, mean ± SD years||71.1 ± 7.0||71.7 ± 6.2||71.0 ± 6.7||72.6 ± 6.3|
| BMI, mean ± SD kg/m2||27.6 ± 4.5||29.3 ± 5.3†||27.7 ± 4.5||30.5 ± 5.3‡|
|Foot function|| || || || |
| Hallux flexor strength, % BW||14.6 (13.4–15.8)||12.6 (11.4–13.8)†||14.3 (13.3–15.2)||11.7 (10.0–13.4)‡|
| Lesser toe flexor strength, % BW||10.5 (9.8–11.3)||9.6 (8.9–10.4)||10.5 (10.0–11.1)||8.8 (7.7–9.8)‡|
| Ankle DF strength, kg||10.7 (10.1–11.3)||9.5 (8.9–10.3)†||10.5 (10.0–10.9)||9.1 (8.2–9.9)‡|
| Ankle DF flexibility, degrees||49.2 (48.0–50.4)||49.8 (48.6–50.0)||49.5 (48.5–50.5)||49.5 (47.8–51.3)|
| Foot reaction time, msec||301 (291–311)||312 (301–322)||300 (292–309)||323 (308–337)‡|
| Walking speed, meters/second||1.03 (1.0–1.06)||0.98 (0.95–1.05)†||1.02 (1.0–1.05)||0.94 (0.9–0.98)‡|
| Stride length, meters||1.19 (1.16–1.21)||1.14 (1.12–1.17)†||1.18 (1.16–1.20)||1.11 (1.08–1.15)‡|
| Step length, cm||59.5 (58.3–60.7)||57.1 (56.0–58.3)†||59.3 (58.3–60.3)||55.6 (53.9–57.3)‡|
| Step width, cm||10.1 (9.6–10.6)||10.3 (9.8–10.7)||10.0 (9.6–10.4)||10.7 (10.0–11.3)|
| Stance time, % GC||61.7 (61.5–62.0)||61.8 (61.5–62.0)||61.6 (61.4–61.9)||62.0 (61.6–62.4)|
| Swing time, % GC||38.3 (38.0–38.6)||38.3 (38.0–38.5)||38.3 (38.1–38.6)||38.0 (37.6–38.4)|
| Double support time, % GC||23.5 (23.0–24.0)||23.9 (23.4–24.4)||23.5 (23.1–23.9)||24.3 (23.6–25.0)‡|
| Single support time, % GC||38.3 (38.0–38.6)||38.0 (37.7–38.3)||38.3 (38.1–38.5)||37.8 (37.4–38.2)‡|
|Postural sway, mm|| || || || |
| Balance on floor||71.4 (65.4–77.5)||78.1 (72.1–84.2)||71.6 (66.6–76.5)||83.9 (75.4–92.3)‡|
| Balance on foam||180 (168–193)||186 (173–198)||176 (166–185)||204 (187–221)‡|
Participants classified with foot pain using Definition A had significantly reduced ankle dorsiflexion and hallux flexor strength compared to those without foot pain (P < 0.02) (Table 1). Ankle flexibility and foot reaction time did not differ between those who had foot pain and those who did not. Postural sway on either the floor or foam surface did not differ between the 2 participant groups; however, stride length, step length, and walking speed were significantly reduced in those with foot pain. Other gait variables such as step width and time spent in the different gait phases did not differ significantly between the foot pain groups. Gait variability, defined as the within-participant SD, did not differ between the participant groups for any of the gait variables (P > 0.05 for all). Interestingly, when using the more conservative cutoff for categorizing disabling foot pain (Definition B), the same variables remained significantly different between those with and without foot pain (ankle dorsiflexion strength, hallux flexor strength, stride length, step length, and walking speed). However, under this more conservative criterion, several additional variables emerged as being associated with disabling foot pain. Compared to the remaining cohort, individuals with disabling foot pain, using Definition B, had significantly reduced flexor strength of the lesser toes, increased foot reaction time, increased postural sway on both the floor and foam surfaces, and an increased time spent in double support combined with decreased time spent in the single support phase of the gait cycle (Table 1). Participants with foot pain, using both definitions, scored significantly lower on the total SF-36 and all subcomponents of this survey (Table 2).
Table 2. SF-36 component scores for foot pain and no pain groups*
|SF-36 component||Definition A||Definition B|
|No pain||Foot pain||Mean difference||No pain||Foot pain||Mean difference|
|Physical functioning||79 (75–82)||66 (63–70)||12 (8–17)†||78 (76–81)||56 (52–61)||22 (17–27)†|
|Role physical||79 (73–85)||61 (55–67)||18 (9–27)†||77 (72–82)||51 (42–59)||26 (16–36)†|
|Body pain||82 (79–86)||64 (60–67)||18 (13–23)†||79 (76–82)||56 (52–61)||22 (17–28)†|
|General health perceptions||78 (75–81)||66 (63–69)||12 (8–16)†||76 (74–79)||59 (55–63)||18 (13–22)†|
|Vitality||73 (70–76)||62 (59–64)||12 (8–15)†||71 (69–73)||56 (53–60)||15 (11–19)†|
|Social functioning||91 (88–95)||83 (79–86)||9 (4–14)†||90 (88–93)||78 (73–82)||13 (7–18)†|
|Role mental||87 (82–92)||76 (71–81)||11 (4–19)‡||87 (83–91)||67 (60–75)||19 (11–28)†|
|Mental health||83 (80–85)||79 (77–81)||4 (0–7)‡||82 (80–84)||77 (73–80)||6 (2–9)‡|
|Dimension 1 (physical)||78 (75–81)||64 (61–66)||15 (11–18)†||76 (74–78)||56 (52–59)||20 (17–25)†|
|Dimension 1 (mental)||83 (80–85)||73 (70–75)||10 (7–13)†||81 (80–83)||67 (64–70)||14 (11–18)†|
|Total||82 (79–84)||69 (67–72)||12 (0–16)†||80 (78–82)||62 (59–66)||18 (14–22)†|
Table 3 shows the breakdown of responses by the participants with foot pain for the individual items of the MFPDI. Of the 10 items characterizing functional problems, the presence of foot pain resulted in a high proportion (>40%) of participants avoiding standing, avoiding hard/rough surfaces, walking slowly, avoiding walking distances, and using the car/bus more. A higher proportion of participants under Definition B were affected by foot pain for all items of the MFPDI. Within the individual constructs, Definition B had a significantly higher number of responses under each item of the functional problems construct except for avoiding walking outside and irritability when feet hurt. The proportion of participants reporting that foot pain affected personal appearance did not differ between the 2 foot pain definitions, and 2 of the 5 items under the pain intensity construct were significantly higher using Definition B (Table 3).
Table 3. Prevalence of disability among people with foot pain for each item of the Manchester Foot Pain and Disability Index*
| ||Definition A||Definition B|
|Functional problems|| || |
| Avoid walking outside||14.3||22.5|
| Avoid walking distances||44.2||67.6†|
| Don't walk normally||30.3||46.8†|
| Walk slowly||46.8||64.2†|
| Have to rest||31.6||54.3†|
| Avoid hard/rough surfaces||49.0||70.9†|
| Avoid standing||50.7||71.6†|
| Use car/bus more||41.8||63.8†|
| Need help with housework/shopping||18.3||30.4†|
| Irritable when feet hurt||35.7||44.5|
|Pain intensity|| || |
| Carry on but in more pain||56.2||76.3†|
| Constant pain in feet||37.4||58.0†|
| Pain worse in morning||29.8||38.0|
| Pain worse in evening||48.4||55.5|
| Shooting pain in feet||29.7||40.7|
|Personal appearance|| || |
| Self-conscious about feet||25.2||34.6|
| Self-conscious about shoes||20.1||28.8|
- Top of page
- SUBJECTS AND METHODS
- AUTHOR CONTRIBUTIONS
Foot pain classified using the traditional MFPDI definition (score ≥1 Definition A) was prevalent in 49.7% of the participants. This prevalence rate is very similar to the 54% reported by Munro and Steele (7), who surveyed older residents within the same regional area to the current study 12 years previously. A recent review article (35) reported the prevalence of foot pain among older people to vary from 10–70%. These between-study differences can be attributed to variations in the definitions of foot pain used in each of the studies. As such, using a more conservative cutoff point for the MFPDI (Definition B) yielded a lower prevalence of disabling foot pain of 26%, the same prevalence rate of foot pain as reported in people age >65 years in the North West Adelaide Health Study (12). The difference in prevalence rates justifies the use of Definition B, as a high proportion of participants with foot pain classified under Definition A probably included people with relatively mild foot pain symptoms. In agreement with several other studies investigating factors associated with foot pain, women and those with a higher BMI were found to have a higher prevalence of foot pain (9, 10, 12).
The extent to which disabling foot pain impacts an individual's ability to carry out activities of daily living is evident in Table 3. Almost half of the participants with foot pain indicated that foot pain resulted in them avoiding hard or rough surfaces, avoiding standing, and caused them to walk more slowly. A higher proportion of participants with disabling foot pain, classified using Definition B, were functionally impaired because of their foot pain on all components of the MFPDI. In particular, the more conservative cutoff was a better discriminator of the functional construct of the MFPDI, whereby the frequency of responses was significantly higher under Definition B for all but 2 items in this construct. Of concern, more than two-thirds of the participants with foot pain avoided hard or rough surfaces, walking distances, and standing because of their foot pain. Participants with foot pain also scored significantly lower on the total SF-36 and all subcomponents (Table 2). Using Definition B further highlighted the difference between those with disabling pain and those without for all components of the SF-36, in particular physical functioning. Similarly, adults with foot symptoms, defined as pain, aching, or stiffness, have been found to record poorer physical function (total Stanford Health Assessment Questionnaire score) than those without foot symptoms (11). Our results support previous studies that have shown an association between foot pain and the physical and mental components of the SF-36 (4, 36), although no other study was located that reported all the individual components of the SF-36. These findings suggest that foot pain not only impedes functional capacity, but is also associated with an overall decreased quality of life, whereby social function, vitality, and mental health status are reduced.
Using the traditional MFPDI criteria for foot pain, no difference in the postural sway tests performed on either the floor or the foam surfaces was observed. Interestingly, when the more conservative cutoff for foot pain was applied, individuals with disabling foot pain displayed significantly greater postural sway on both tests. Menz and Lord (17) found no difference when using the same balance tests between older people with (n = 27) and without (n = 108) foot pain, although foot pain was assessed as a simple yes/no response. They did, however, find that those with foot pain performed more poorly on a coordinated stability task and other functional tests (stair ascent/descent, alternate step-up, timed 6-minute walk), which was consistent with our present findings of impaired functional ability with foot pain.
Reducing walking speed is a well-established compensatory mechanism in individuals with foot pain (6, 17, 37). The reduced step/stride length and walking speed evident in these older people with foot pain may be partly attributed to the reduced foot and ankle muscle strength also evident in this group. Toe flexor weakness will reduce an individual's ability to control shifts of body weight and propel the body forward during walking, whereas ankle dorsiflexor weakness may reduce the ability to lift the foot and toes off the ground during the swing phase of gait to avoid tripping. Furthermore, our prospective falls study on the same cohort of older people as in the current study identified muscle weakness of the hallux and lesser toes as fall risk factors (25). Therefore, these findings suggest that foot and ankle muscle weakness in older people with foot pain may contribute to an increased risk of falling.
The causal link between muscle weakness and foot pain cannot be determined from this study. Although it is possible that reductions in mobility in those with foot pain may lead to muscle atrophy through disuse, it is also possible that pain inhibits the ability of the individuals to optimally perform the strength assessment tasks. This needs to be taken into consideration when providing interventions to individuals with disabling foot pain. Although it is important to address muscle weakness in those with foot pain, strength gains may be limited if pain inhibits the ability to perform prescribed exercises and is likely to compromise adherence. Therefore, it could be argued that interventions directed toward this population should combine treatment of foot pain with strengthening of the foot and ankle musculature in order to improve functional capacity.
It must be acknowledged that this study focused solely on foot pain and did not take into consideration musculoskeletal pain or disorders at other joints. However, individuals with foot pain, regardless of definition, scored significantly worse on the body pain component of the SF-36, indicating they experienced body pain more than those without foot pain. Studies have suggested that older adults with disabling foot pain are more likely to report pain in other parts of the body (back, hips, knees, and hands or wrists) (4, 10). Furthermore, multijoint pathologies have been found to increase the risk of functional impairment to a greater extent than single joint problems (38). Similarly, no specific measure of depression was taken and therefore it could not be adjusted for in the analyses. Fifty-six to 76% of the participants with foot pain (Definition A and B, respectively) reported carrying on with daily activities, but in more pain (Table 3). Older adults with foot pain should therefore be encouraged to seek professional treatment for their feet. Despite the fact that two-thirds of the participants with foot pain visited medical personnel about their feet, it appears that the remaining individuals may be ignoring their symptoms. Definition B, at least 1 item scored as on most/every day(s) (24), was a better discriminator of those with more disabling foot pain and functional limitation, and may therefore be the most appropriate definition to identify older people who may require treatment for their foot pain.
In conclusion, older people with disabling foot pain exhibit reduced quality of life, functional impairment, and altered foot characteristics, in particular reduced foot and ankle muscle strength. It is possible that these alterations to foot function, in addition to poorer balance in those with more severe foot pain, may contribute to impaired mobility and an increased risk of falling. Providing interventions to older people to treat foot pain and improve foot function may therefore play a role in reducing the progression of functional decline and improving quality of life.
- Top of page
- SUBJECTS AND METHODS
- AUTHOR CONTRIBUTIONS
All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be submitted for publication. Dr. Mickle had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study conception and design. Mickle, Munro, Lord, Menz, Steele.
Acquisition of data. Mickle.
Analysis and interpretation of data. Mickle, Munro, Menz, Steele.