Foot Pressures, Peripheral Neuropathy, and Joint Mobility in Asian and Europid Patients With Diabetes

Abstract: Objective. A cross sectional study was developed to investigate ethnic differences in foot pressure and joint mobility in non-diabetic and diabetic subjects with and without neuropathy in a hospital-based diabetes clinic. Methods. The subject groups consisted of a volunteer sample of 10 Asians (AC), 11 Europid non-diabetic controls (C), a consecutive sample of 12 Asians (ADC) and 11 Europid (DC) non-neuropathic patients, and 12 Asian (ADN) and 13 Europid (DN) neuropathic diabetic patients. All subjects were matched with respect to age and gender. The main outcome measures were foot pressures and joint mobility. Results. Peak foot pressure was increased in DN (1150 ± 412 kPa, mean ± SD) compared to AC, ADC, ADN, C, and DC (510 ± 164 kPa, 673 ± 331 kPa, 623 ± 222 kPa, 707 ± 240 kPa, 793 ± 196 kPa, respectively; P < 0.05). Passive range of motion of the subtalar joint, ankle (AC only), and first metatarsophalangeal and fifth metacarpophalangeal joints (MCJP) were reduced in DN compared to the Asian controls and diabetic patients (P < 0.05). Dynamic ankle and rearfoot (subtalar) joint angles were not different among groups. Only the fifth MCJP extension had an effect on peak plantar pressure while controlling for ethnicity (P < 0.05). Conclusion. Peak foot pressure was higher and joint mobility was lower in Europid compared to Asian diabetic neuropathic patients; however, no relationship was observed between reduced foot joint mobility and increased foot pressures. The association between fifth MCJP extension and peak pressure suggests that fifth MCJP extension may be used as a screening method for increased pressure. The low foot pressures exhibited by the Asian subjects are most likely caused by factors other than those investigated in this study.   Diabetic foot ulceration and amputation remain among the most serious and debilitating long-term complications of diabetes. Foot ulceration has previously been demonstrated to be related to limited joint mobility in the joints of the foot.^1,2 Range of motion reduction in different joints is known to develop as a chronic complication of diabetes with changes in the hand of diabetic patients first described in 1957.³ Changes in the hand do not have any immediate clinical implications; however, they have been reported to be significantly associated with other chronic complications of diabetes. Several other reports have shown that reduced range of motion also develops in the foot joints.^4–6 Development of reduced joint mobility has been attributed to non-enzymatic glycation of collagen resulting in thickening of skin, tendons, ligaments, and joint capsules, which reduces tissue flexibility.^7,8   Joint mobility is defined as a joint’s range of motion, and is related to age, sex, and ethnic background.^9–11 Limited joint mobility (LJM) has been associated with diabetic foot ulceration^4,12 and increased plantar foot pressures,⁵ while increased foot pressures are predictive of foot ulceration.^13,14 Normal mobility of the subtalar joint is crucial to the biomechanics of the foot, as subtalar joint pronation during heel strike is a major shock-absorbing mechanism. If the foot is supinated when it should be pronated due to LJM or structural abnormality, flexibility and shock absorption will be compromised.^15,16   Inhabitants of the Asian subcontinents exhibit greater joint mobility compared to Europids.^9,10,17 Furthermore, it has been suggested that diabetic patients from the Asian subcontinents have a lower prevalence of foot ulceration and amputation than their Europid counterparts.^18–20 The lower prevalence of foot ulceration may be related to greater joint mobility and associated lower foot pressures, as both have been reported in Asians, Blacks, and Hispanics.^6,20–22   Thus, preliminary evidence exists to suggest an association between joint mobility and plantar pressures, while high plantar pressures are predictive of foot ulceration. Whether ethnic differences in joint mobility play a role in the distribution of plantar pressures and foot ulcer development in diabetic patients remains to be answered. Therefore, the primary aim of this study was to investigate ethnic differences in peak plantar pressure among Asian and Europid non-diabetic and diabetic patients with and without neuropathy. A secondary goal of this study was to investigate ethnic differences in joint mobility and the relationship between passive and dynamic range of motion and plantar pressure.

Methods

  The local ethics committee approved the study protocol. All subjects received complete information about the study before giving written consent to participate. All subjects underwent a neuropathic and vascular evaluation, assessment of passive range of motion of three joints in the foot and one in the hand, foot pressure measurements during barefoot walking, and kinematic analysis of the ankle and rearfoot joint angle during walking.   Subjects. Seventy subjects attending the Manchester Diabetes Centre were studied, including 10 Asian (AC) and 11 Europid non-diabetic controls (C), 12 Asian (ADC) and 12 Europid (DC) diabetic non-neuropathic patients, and 12 Asian (ADN) and 13 Europid (DN) neuropathic diabetic patients. Patients and controls were classified as Asian if their parents and three out of four of their grandparents originated from an Indian sub-continent (ie, India, Pakistan, Bangladesh, or Sri Lanka). All but one of the Asian subjects were born in the Indian subcontinent. Exclusion criteria were active foot ulceration, foot deformities, significant peripheral vascular disease (absent foot pulses), or inability to walk normally or unaided. The patients were otherwise unselected.   History. Information collected during the study visit was duration and treatment of diabetes, history of ulceration, presence of callus, and smoking habits. In order to assess the effect of cultural differences in foot care, all subjects were asked about the frequency of washing their feet. All subjects’ feet were checked for callus, muscle wasting, and foot deformities.   Neuropathic evaluation. The neuropathic evaluation comprised of measurement of Pressure Perception Threshold (PPT) on the plantar surface of the foot using Semmes-Weinstein monofilaments, warm Temperature Perception Threshold (TPT) on the dorsum of the foot using the thermo-aesthesiometer, Vibration Perception Threshold (VPT) at the pulp of the hallux using the Neurothesiometer (Horwell, Nottingham, UK), and the Peroneal Motor Nerve Conduction Velocity (MNCV) using the Medelec 92a device (Medelec, Ltd., Surrey, UK). Neuropathy was defined as MNCV < 40 m/s and/or 2 out of 3 abnormal test results for VPT, TPT, and PPT.^23,24 Abnormal results were defined as VPT > 25 V, TPT > 2˚C, PPT ≥ 10 g (monofilament 5.07). The limit of VPT was chosen, as this threshold is commonly used and is predictive of foot ulceration.^25,26 The limits of PPT and TPT correspond to mean ± 2 SDs of healthy control subjects in the authors’ laboratory.   Foot pressure. Pressure data was collected while subjects walked over the optical Pedobarograph platform (Department of Medical Physics and Clinical Engineering, Royal Hallamshire Hospital, Sheffield, UK) built on a 5-m long walkway.²⁷ Pressure was measured with a frequency of 25 Hz and was measured from the second or third step after the start of walking. Subjects practiced until he or she walked in a normal, comfortable pattern. Although walking speed has been reported to be a substantial factor in determining peak pressure,²⁸ it was decided not to control walking speed in this study, as this would interfere with the subjects’ normal walking pattern. Any steps the investigator regarded as atypical or out of balance were not saved, and therefore, excluded from the analysis.   Plantar pressure data were analyzed in seven areas of the foot: the heel, all five metatarsal heads, and the hallux. The peak pressures of all areas were determined and the highest pressure of all sites (ie, peak pressure of the entire foot) was determined and subsequently selected as the dependent variable for the analysis of covariance (ANCOVA). Peak pressure was chosen as the dependent variable because a number of studies have shown, prospectively or retrospectively, that abnormal peak pressures can predict foot ulceration and that abnormal peak pressure exists at sites of previous ulceration.^13,29 Although many other pressure variables can be used for analysis, no other pressure variable has been proven to be related to foot ulceration. The peak plantar pressure values were natural log (ln) transformed to meet the assumptions of ANCOVA analysis (normal distribution of the response variable and constant error variance).   Passive range of motion (passive ROM). All patients and control subjects were tested for passive ROM of four joints: the subtalar, ankle, first metatarsophalangeal joint (MTPJ), and the fifth metacarpophalangeal joint (MCPJ). Each measurement was made in triplicate; the mean of maximal range of movement was used for further analysis.   The joint mobility of the subtalar and ankle joint was measured while the subject was in prone position on an examination bed with the ankle joint extended over the end of the bed and the knee placed in the frontal plane. For subtalar joint assessment, the lower one third of the leg and heel were marked by bisecting the medial and lateral margins of the leg and calcaneus followed by connecting the marks with a line. The foot was placed at a right angle to the leg, as inadvertent plantar flexion of the foot introduces additional frontal plane motion to the ankle, thereby inaccurately increasing the total range of subtalar joint motion. The goniometer was placed with its central point at the level of the subtalar joint and the calcaneus was passively moved into its end range of inversion and eversion motions.30 End range of motion was determined by firm end-feel position. The maximum degrees of inversion and eversion were noted, and the passive ROM was determined by adding the maximum degrees of inversion and eversion.   For the ankle joint assessment, the skin was marked at the head of the fibula, the lateral malleolus, and the fifth metatarsal head. The axis of the goniometer was placed over the lateral malleolus and one arm was aligned with the fibula head and the other arm was aligned with the fifth metatarsal head.^31,32 The ankle joint was passively moved to the end range of motion of dorsiflexion and plantar flexion. This method has demonstrated its reliability in the past.³³ Care was taken not to inappropriately pronate or supinate the subtalar joint while measuring dorsiflexion, as this could affect the measurement of passive ROM (pronation allows the oblique axis to dorsiflex, thus measuring greater passive ROM).³⁰ Ankle passive ROM was defined as the maximum degree of plantar flexion minus the maximum degree of dorsiflexion.   Passive range of motion of the first metatarsophalangeal joint (first MTPJ) was measured with the subject in a supine position with the foot and ankle extended over the examination bed. After palpation, lines bisecting the shaft of the first metatarsal and the proximal phalanx of the hallux were drawn on the medial side of the foot. The axis of the goniometer was placed at the first metatarsophalangeal joint, one axis was aligned with the shaft of the first metatarsal and the other with the proximal phalanx of the hallux.^30,34,35 The hallux was maximally dorsi-flexed and plantar flexed to a firm end position. The passive ROM was defined as the maximum degree of plantarflexion minus the maximum degree of dorsiflexion. Maximum dorsiflexion (first MTPJ extension) was also used for analysis.   Joint mobility of the fifth metacarpophalangeal joint (fifth MCPJ) was assessed with the subject’s hand placed flat on a table. The fifth finger was extended to a firm end position while ensuring that the hand remained flat on the table. The maximum extension was defined as the angle between the proximal phalanx of the fifth metacarpal and the table surface. This technique has been reported reliable using a finger goniometer.³⁶   Dynamic range of motion (dynamic ROM). Kinematic data and plantar pressure measurements were collected simultaneously during five walking trials at each subject’s selected pace. Kinematic data (50 Hz) was collected using two super VHS video cameras (Panasonic NV-MS4)—one in the frontal plane for 2-D assessment of the subtalar joint and one in the sagittal plane for the ankle joint. Both cameras were in a standardized position 5 m from and perpendicular to the Pedobarograph plate. Foot pressure measurements and video recordings consisted of five steps of the left foot; however, only data from three left footsteps were used for analysis, as not all data were deemed sufficient for analysis (ie, data were only used if both the video and pressure measurements had acceptable quality for analysis). Thus, if kinematic data had to be disregarded from a trial, then consequently, the pressure data of this trial were disregarded as well.   For the measurement of the dynamic joint movement, the same joint markers were used as for the passive joint ROM. The ankle joint angle was defined and calculated as the angle between the lines connecting the markers at the fifth metatarsal head, the lateral malleoli, and the head of the fibula. The following parameters were obtained from the video recordings for the ankle joint: angle at heel strike, rate of plantar flexion after heel strike, maximum dorsiflexion during midstance, range of motion, and average plantar flexion angular velocity at the end stance phase.   The 2-D kinematic assessment limited the subtalar joint motion analysis to measurement of rearfoot angles (ie, heel inversion and eversion). Therefore, dynamic subtalar joint motion will be referred to as “rearfoot angle” in this report. Rearfoot eversion and inversion angles were defined as the angle formed by one line bisecting the lower leg and a second line bisecting the calcaneus. For the rearfoot angle, only data of the first 60% of the stance phase were used for analysis, as up to 60% of stance has previously been shown to be comparable to 3-D obtained rearfoot motion data.^37,38 However, as the most important phase for shock absorption is during the first 25% of the gait cycle,³⁹ the data available should be sufficient to achieve the aims of this study. The following parameters of the rearfoot angle were obtained from the video recordings: rearfoot angle at heel strike, maximum pronation (heel eversion), and range of motion during the first 60% of stance.   Repeatability of joint mobility measurements and foot pressures. Between-measurement-reliability of passive ROM for each subject was measured as intraclass correlation coefficient (ICC) and was obtained from the 3 measurements taken at the end range of movement at each joint. To determine between-trial reliability of dynamic joint angles and foot pressures for each subject, intraclass correlation coefficients (ICCs) were calculated on the three trials used for analysis.

Data Analysis

  Video data was digitized using Ariel Performance Analysis System (APAS) software (Version 1.0) to obtain the coordinates of the joint markers. Software was written to calculate the joint angles for the ankle and subtalar joint from the coordinates of the markers. The raw data were then smoothed using a digital filter with a cut-off frequency of 6 Hz (using APAS software). The average of the three trials for each subject was used for analysis of joint angles. The joint angles were filtered using a fourth-order Butterworth filter with a cut-off frequency of 6 Hz using Matlab software (version 5.2); these data were subsequently used for analysis. The joint angles were time normalized by interpolation so that 100% corresponded with the duration of the stance phase and were then averaged for the different subject groups (Matlab Version 5.2).   For statistical analysis of differences between subject groups, a one-way ANOVA/Tukey’s HSD test for post-hoc multiple comparisons with a significance level of 0.05 was used (SPSS 10.0). Using ANCOVA, the effect of ethnicity and neuropathy on the relationship between joint mobility and peak pressure of the foot was analysed, using a significance level of 0.05 (SPSS 10.0).

Results

  Patients. All subjects were matched with respect to age and body mass (Table 1). There was no difference in duration of diabetes and severity of neuropathy between Asian and Europid diabetic neuropathic patients. The Asian subjects (as one group) washed their feet on average 4.3 times more than the Europid subjects (P < 0.05; Tables 1 and 2).   Reliability joint mobility measurements. The ICCs for the passive joint mobility measurements ranged between 0.92 and 0.99 (Table 3a). The ICCs for dynamic rearfoot angles were 0.82 for rearfoot ROM (during first 60% stance phase), 0.97 for rearfoot angle at heel strike and 0.97 for max rearfoot eversion during stance (during first 60% stance phase; Table 3b). Reliability for the dynamic ankle joint angles were calculated as the following ICCs: 0.90 for ankle ROM, 0.97 for ankle angle at heel strike, 0.84 for ankle plantar flexion after heel strike, 0.95 for maximum dorsiflexion during midstance and 0.91 for average plantar flexion angular velocity (Table 3b). The ICCs for peak plantar pressures ranged between 0.81 and 0.99 for the different regions (Table 3c). The strong ICCs indicate that passive and dynamic joint mobility and foot pressures could reliably be measured.   Plantar pressure. The peak plantar pressure of the whole foot and each individual site are shown in Figure 1. Peak plantar pressure of the whole foot was higher in DN compared to AC, ADC, ADN, C, and DC (mean peak pressures were respectively 1150 vs. 510, 672, 623, 707, and 793 kPa; P < 0.05), with similar trends observed for most individual regions in the foot (Figure 1). Peak pressures were significantly higher in DN compared to ADN in the heel and first, second, third, and fifth metatarsal head area (P < 0.05).   There were no significant differences in peak pressure at any site among the three Asian subject groups. The Europid neuropathic patients had significantly higher pressures compared to their non-diabetic counterparts for the whole foot, first, second, and fifth metatarsal head, and compared to their non-neuropathic counterparts for the whole foot, first, and fifth metatarsal head (P < 0.05). The peak pressure of the whole foot was higher in subjects with presence of callus (mean ± SD; 886 ± 354 kPa) compared to subjects without callus (668 ± 308 kPa; P < 0.01) when analysing the whole study population analysed as one group. The difference in peak pressure was not significant when analysed separately for the Asian and Europid group.   Passive range of motion. The Asian non-diabetic controls (AC) and diabetic patients (ADC and ADN) had greater average passive subtalar ROM than the Europid diabetic controls (DC) and neuropathic patients ([DN], 28.1, 23.4, and 27.4 vs. 19.3 and 19.8 degrees, [P < 0.01], not significant for ADC; Figure 2). A trend toward reduced ankle passive ROM in the Europid diabetic patients compared to their non-diabetic counterparts was observed; however, there were no significant differences between any of the groups (Figure 2). The passive ROM of the first MTPJ was greater in Asian non-diabetic controls compared to Europid diabetic controls and neuropathic patients (DC and DN) (112.3 vs. 83.3 and 79.2 degrees), and ADC vs. DN (97.6 vs. 79.2 degrees; P < 0.05). The greatest maximum extension (dorsiflexion) of the first MTPJ was measured in the Asian non-diabetic subjects, but this was not significantly different from any other group (Figure 2). The extension of the fifth MCPJ was lower in DN compared to all Asian groups (25.6 vs. 49.7, 39.9, and 44.2 degrees; P < 0.05).   Dynamic range of motion. The average stance duration was not significantly different between any of the groups (Table 4). The overall patterns of the rearfoot (subtalar) and ankle joint angle during stance followed the normal patterns as previously reported (Figure 3).^38,40,41 The rearfoot (subtalar joint) is slightly inverted at heel strike. After heel strike, the rearfoot everts (subtalar joint pronates) and reaches maximum eversion (pronation) between 33% and 52% of the stance phase duration. There were no differences in dynamic ROM of the rearfoot and ankle joint between groups (Tables 4 and 5, Figure 3).   Effect of ethnicity. When controlling for ethnicity, extension of the fifth MCPJ was the only measurement of passive joint mobility that had a significant effect on peak pressure of the foot (P < 0.05). Passive ROM of the subtalar, ankle, and first MTPJ joint did not have a significant effect on peak pressure of the foot when controlled for ethnicity. However, for each of the relationships between passive ROM of the subtalar, ankle, first MTP, and fifth MCP joint with peak foot pressure there was a significant effect of ethnicity (P < 0.01).   These differences were maintained when neuropathic status was added to the model, demonstrating that ethnicity had an independent effect on peak pressure (P < 0.01). Conversely, there was a significant effect of neuropathy independently of ethnicity on peak pressure (P < 0.05). None of the joint mobility measurements had a significant effect on peak pressure when controlling for both ethnicity and neuropathy.   Because there was no interaction between ethnicity and neuropathy, the effect of neuropathic status on peak pressure seems to be the same across the two ethnic groups. In other words, the effect of ethnicity on peak pressure is the same regardless of neuropathy.   The multiple regression model controlling for ethnicity and including fifth MCPJ extension as the independent variable, explained 31% of the variance of peak pressure. When controlling for both ethnicity and neuropathy the multiple regression model, including fifth MCPJ extension as the independent variable, explained 38% of the variance of peak pressure.   There was no effect of any of the dynamic range of motion variables of the rearfoot and ankle joint on peak pressure when controlled for ethnicity or when controlling for both ethnicity and neuropathy.

Discussion

  In the present study ethnic differences in foot pressures were investigated, as well as ethnic differences in joint mobility that were measured passively and during walking. Additionally, the relationship between joint mobility (as measured passively and during walking) and plantar pressure was explored.   The results of this study show lower peak pressures and a greater joint mobility (passive ROM) in Asian diabetic neuropathic patients compared to their Europid counterparts, which is in agreement with previous studies.^6,20–22 However, although peak pressure was lower in the Asian subjects, greater joint mobility in the foot was not found to be associated with lower peak pressures. Extension of the fifth MCPJ was the only passive ROM measurement with a significant effect on peak plantar pressure, suggesting that this simple measurement may be used to screen for high foot pressure. Extension of the fifth MCPJ was strongly associated with passive ROM measurements in the foot; therefore, it is possible that joint mobility in the hand is a more sensitive measurement for general limited joint mobility because the fifth MCPJ is usually the first joint to be affected.⁴²   In contrast to our findings, previous studies have suggested a correlation between reduced foot joint mobility, increased foot pressure, and foot ulceration.^4,5,12 Perhaps joint mobility in the foot (ankle and subtalar joint) in our study population was not limited to the extent that it could have compromised foot function and therefore increased plantar pressure. The finding of no difference in dynamic ROM in rearfoot and ankle joint between the studied groups in the current study is in line with this view. In support of the present findings, Turner et al⁴³ also reported no direct relation between limited joint mobility and increased foot pressure. They showed, even in cases of significant reduction in passive ankle ROM in diabetic patients, that gait ROM (dynamic ROM) was not different from control subjects and not correlated with plantar pressure. Although Orendurff and associates44 did report a relation between ankle equines (ankle plantar flexion contracture), they showed that it only accounted for a small proportion of the variance of pressure, suggesting that there is only a limited role for ankle equines in increasing forefoot pressure. Similarly, with regards to mobility of the first MTPJ, which was the most reduced in the Europid neuropathic patients in the current study, would just have been enough motion as is required for normal gait.^35,45   In the literature, two different walking “styles” have been reported to affect peak plantar pressure, although both styles probably have much in common. Shuffling and using a “hip strategy” as opposed to normal walking and using an “ankle strategy” have both been reported to lower the peak pressure within the same subject.^46,47 While it is possible that a different “style” of walking may have been used by the Asian participants in our study, resulting into lower foot pressures, this is unlikely since no differences in dynamic ankle ROM was observed.   The results of the present study suggest that the existence of high plantar pressure is rare among the Asian population, since no abnormally high pressures (> 1230 kPa using same pressure device)⁴⁸ were recorded in the Asian participants in contrast to 46% (6/13) on the Europid neuropathic group. It is possible that the Asian population possesses other (biomechanical) differences not assessed in the present study, (ie, foot structure and gait characteristics), which might explain the lower foot pressures as measured in this group.   A limitation of the current study was that walking speed was not controlled. Although this could have affected plantar pressure, a difference in walking speed is unlikely to exist, as there were no differences in stance duration among the groups. Stance duration has been used as a surrogate measure of walking speed, as a strong correlation between ground contact time and walking speed has previously been reported (r = -0.86).²⁸

Conclusion

  The results of this study suggest that foot pressure is increased in Europid diabetic neuropathic patients when compared to their non-neuropathic and Asian counterparts. However, foot pressure in the Asian diabetic neuropathic patients was not increased compared to their non-diabetic and non-neuropathic counterparts. The results also suggest that reduced mobility in the foot joints was not associated with increased plantar pressure, as only joint mobility of the hand showed a significant effect on peak pressure when controlling for ethnicity. This finding suggests that hand joint mobility may be used as a screening tool for increased pressure. While greater joint mobility exists in Asian subjects, this does not appear to be used by the rearfoot and ankle joint during gait. Therefore, this greater joint mobility may not have an effect on foot pressure, suggesting that variables other than those measured in this study cause the differences in plantar pressure among Asian and Europid subjects.

Acknowledgements

  Dr. van Schie received partial funding from Research & Development, National Health Service, North West Executive Scheme, UK. Support for this study was also provided by the National Health Service Research and Development Levy.

References

1. Mueller MJ, Minor SD, Diamond JE, Blair VP. Relationship of foot deformity to ulcer location in patients with diabetes mellitus. Phys Ther. 1990;70(6):356–362. 2. Birke JA, Franks BD, Foto JG. First ray joint limitation, pressure, and ulceration of the first metatarsal head in diabetes mellitus. Foot Ankle Int. 1995;16(5):277–284. 3. Lundbaek L. Stiff hands in longterm diabetes. Acta Med Scand. 1957;158:447–451. 4. Delbridge L, Perry P, Marr S, et al. Limited joint mobility in the diabetic foot: relationship to neuropathic ulceration. Diabet Med. 1988;5(4):333–337. 5. Fernando DJ, Masson EA, Veves A, Boulton AJ. Relationship of limited joint mobility to abnormal foot pressures and diabetic foot ulceration. Diabetes Care. 1991;14(1):8–11. 6. Veves A, Sarnow MR, Giurini JM, et al. Differences in joint mobility and foot pressures between black and white diabetic patients. Diabetic Med. 1995;12(7):585–589. 7. Crisp AJ, Heathcote JG. Connective tissue abnormalities in diabetes mellitus. J R Coll Physicians Lond. 1984;18(2):132–141. 8. Vlassara H, Brownlee M, Cerami A. Nonenzymatic glycosylation: role in the pathogenesis of diabetic complications. Clin Chem. 1986;32(10):B37–B41. 9. Wordsworth P, Ogilvie D, Smith R, Sykes B. Joint mobility with particular reference to racial variation and inherited connective tissue disorders. Br J Rheumatol. 1987;26(1):9–12. 10. Pountain G. Musculoskeletal pain in Omanis, and the relationship to joint mobility and body mass index. Br J Rheumatol. 1992;31(2):81–85. 11. Vandervoort AA, Chesworth BM, Cunningham DA, Paterson DH, Rechnitzer PA, Koval JJ. Age and sex effects on mobility of the human ankle. J Gerontol. 1992;47(1):M17–M21. 12. Mueller MJ, Diamond JE, Delitto A, Sinacore DR. Insensitivity, limited joint mobility, and plantar ulcers in patients with diabetes mellitus. Phys Ther. 1989;69(6):453–462. 13. Veves A, Murray HJ, Young MJ, Boulton AJM. The risk of foot ulceration in diabetic patients with high foot pressures: a prospective study. Diabetologia. 1992;35(7):660–663. 14. Pham H, Armstrong DG, Harvey C, Harkless LB, Giurini JM, Veves A. Screening techniques to identify people at high risk for diabetic foot ulceration: a prospective multicenter: a prospective multicenter trial. Diabetes Care. 2000;23(5):606–611. 15. Nack JD, Phillips RD. Shock absorption. Clin Podiatr Med Surg. 1990;7(2):391–397. 16. Bevans JS. Biomechanics: a review of foot function in gait. Foot. 1992;2:79–82. 17. Beighton P, Solomon L, Soskolne. Articular mobility in an African population. Ann Rheum Dis. 1973;32(5):413–418. 18. Gujral JS, McNally PG, O’Malley BP, Burden AC. Ethnic differences in the incidence of lower extremity amputation secondary to diabetes mellitus. Diabetic Med. 1992;10(3):271–274. 19. Clarke D, Martin K, Kaltas G, Tindall H. Ethnic variation in the diabetic foot clinic [Abstract]. Diabetic Med. 1992;9(Suppl 1):35A. 20. Toledano H, Young MJ, Veves A, Boulton AJM. Why do Asian diabetic patients have fewer foot ulcers than Caucasians? [Abstract]. Diabetic Med. 1993;10(Suppl 1):S38. 21. Frykberg RG, Lavery LA, Pham H, Harvey C, Harkless L, Veves A. Role of neuropathy and high foot pressures in diabetic foot ulceration. Diabetes Care. 1998;21(10):1714–1719. 22. Widdows P. Ethnic differences in the risk factors associated with diabetes related foot ulceration. In: Proceedings of the 6th Malvern Diabetic Foot conference; May 15–17, 1996; Malvern, UK. 23. Partanen J, Niskanen L, Lehtinen J, Mervaala E, Siitonen O, Uusitupa M. Natural history of peripheral neuropathy in patients with non-insulin-dependent diabetes mellitus. N Eng J Med. 1995;333(2):89–94. 24. Ziegler D, Cicmir I, Mayer P, Wiefels K, Gries FA. The natural course of peripheral and autonomic neural function during the first two years after diagnosis of Type 1 diabetes. Klin Wochenschr. 1988;66(21):1085–1092. 25. Young MJ, Breddy JL, Veves A, Boulton AJ. The prediction of diabetic neuropathic foot ulceration using vibration perception thresholds. A prospective study. Diabetes Care.1994;17(6):557–560. 26. Abbott CA, Vileikyte L, Williamson S, Carrington AL, Boulton AJ. Multicenter study of the incidence of and predictive risk factors for diabetic neuropathic foot ulceration. Diabetes Care. 1998;21(7):1071–1075. 27. Veves A, Boulton AJ. The optical pedobarograph. Clin Podiatr Med Surg. 1993;10(3):463–470. 28. Rosenbaum D, Hautmann S, Gold M, Claes L. Effects of walking speed on plantar pressure patterns and hindfoot angular motion. Gait Posture. 1994;2(3):191–197. 29. Boulton AJ, Hardisty CA, Betts RP et al. Dynamic foot pressure and other studies as diagnostic and management aids in diabetic neuropathy. Diabetes Care. 1983;6(1):26–33. 30. Gastwirth BW. Biomechanical examination of the foot and lower extremity. In: Valmassy RL, ed. Clinical Biomechanics of the Lower Extremities. St. Louis, MO: Mosby Year Book; 1996:132–147. 31. Mueller MJ, Minor SD, Sahrmann SA, Schaaf JA, Strube MJ. Differences in the gait characteristics of patients with diabetes and peripheral neuropathy compared with age-matched controls. Phys Ther. 1994;74(4):299–308. 32. Mueller MJ, Minor SD, Schaaf JA, Strube MJ, Sahrmann SA. Relationship of plantar-flexor peak torque and dorsiflexion range of motion to kinetic variables during walking. Phys Ther. 1995;75(8): 684–693. 33. Diamond JE, Mueller MJ, Delitto A, Sinacore DR. Reliability of a diabetic foot evaluation. Phys Ther. 1989;69(10):797–802. 34. Buell T, Green DR, Risser J. Measurement of the first metatarsophalangeal joint range of motion. J Am Podiatr Med Assoc. 1988;78(9):439–448. 35. Hopson MM, McPoil TG, Cornwall MW. Motion of the first metatarsophalangeal joint. Reliability of four measurement techniques. J Am Podiatr Med Assoc. 1995;85(4):198–204. 36. Slama G, Letanoux M, Thibult N, Goldgewicht C, Eschwege E, Tchobroutsky G. Quantification of early subclinical limited joint mobility in diabetes mellitus. Diabetes Care. 1985;8(4):329–332. 37. Cornwall MW, McPoil TG. Comparison of 2-dimensional and 3-dimensional rearfoot motion during walking. Clin Biomch (Bristol, Avon). 1995;10(1):36–40. 38. Mannon K, Anderson T, Cheetham P, Cornwall MW, McPoil TG. A comparison of two motion analysis systems for the measurement of two-dimensional rearfoot motion during walking. Foot Ankle Int. 1997;18(7):427–431. 39. Langer S, Wernick J, eds. A Practical Manual for a Basic Approach to Foot Biomechanics. 3rd ed. England: Langer Biomechanics Group (UK) Ltd.; 1989. 40. McPoil T, Cornwall MW. Relationship between neutral subtalar joint position and pattern of rearfoot motion during walking. Foot and Ankle. 1994;15(3)141–145. 41. McPoil TG, Cornwall MW. The relationship between three static angles of the rearfoot and the pattern of rearfoot motion during walking. J Orthop Sports Phys Ther. 1996;23(6):370–375. 42. Rosenbloom AL, Silverstein JH, Lezotte DC, Richardson K, McCallum M. Limited joint mobility in childhood diabetes mellitus indicates increased risk for microvascular disease. New Eng J Med. 1981;305(4):191–194. 43. Turner DE, Helliwell PS, Burton AK, Woodburn J. The relationship between passive range of motion and range of motion during gait and platnar pressure measurements. Diabetic Med. 2007;24(11):1240–1246. 44. Orendurff MS, Rohr ES, Sangeorzan BJ, Weaver K, Czerniecki JM. An equinus deformity of the ankle accounts for only a small amount of the increased forefoot plantar pressure in patients with diabetes. J Bone Joint Surg Br. 2006;88(1): 65–68. 45. Hetherington VJ, Johnson RE, Albritton JS. Necessary dorsiflexion of the first metatarsophalangeal joint during gait. J Foot Surg. 1990;29(3):218–222. 46. Mueller MJ, Sinacore DR, Hoogstrate S, Daly L. Hip and ankle strategies: effect on peak plantar pressures and implications for neuropathic ulceration. Arch Phys Med Rehabil. 1994;75(11):1196–1200. 47. Zhu HS, Wertsch JJ, Harris GF, Loftsgaarden JD, Price MB. Foot pressure distribution during walking and shuffling. Arch Phys Med Rehabil. 1991;72(6): 390–397. 48. Veves A, Fernando DJS, Walewski P, Boulton AJM. A study of plantar pressures in a diabetic clinic population. Foot. 1991;2:89–92. Dr. van Schie and Dr. Boulton are from the 1University Department of Medicine, Manchester Royal Infirmary, Manchester, United Kingdom; Dr. van der Linden is from theSchool of Health Care Professions, University of Salford, United Kingdom Address correspondence to: Carine van Schie, PhD Dutch Burns Foundation PO Box 1015 1940 EA Beverwijk The Netherlands Email: cvanschie@burns.nl