An acute lateral ankle sprain is one of the most common sport-related injuries (16), with many patients subsequently complaining of residual symptoms. According to a systematic review, 25% of all patients still experience pain and up to 34% report at least one resprain 3 yr after the initial sprain. In addition, up to 33%–53% of patients who sustained an acute ankle sprain develop a residual condition called chronic ankle instability (CAI) (36). CAI has been defined as the repetitive occurrence of instability, resulting in numerous ankle sprains (14). The instability is characterized by the subjective feeling of the ankle “giving way,” which refers to “the regular occurrence of uncontrolled and unpredictable episodes of excessive inversion of the rear foot, which do not result in an acute lateral ankle sprain” (5). This condition has an effect on sport participation, possibly leading to a lower level of performance or even a change of sport (1,20). Furthermore, recurrent lateral ankle sprains are the primary cause of ligamentous posttraumatic ankle osteoarthritis (34). Therefore, understanding the underlying mechanisms contributing to CAI is crucial for prevention and treatment purposes.
Altered kinematics of the ankle joint during walking and running have been reported to play a role in the underlying mechanisms of CAI. During walking, a more inverted position of the foot in the frontal plane has been found before, at, and immediately after heel strike and even throughout the whole gait cycle in patients with CAI (6,24). For running conditions, a more inverted position of the ankle has been found only in the prelanding phase (22), along with a limited dorsiflexion range of motion at the ankle joint during the stance phase (10). Drewes et al. (11) showed more rear foot inversion, however, throughout the whole gait cycle of jogging in patients with CAI. Furthermore, when comparing different instability groups and subjects with a history of an ankle sprain without CAI symptoms, no significant differences were shown in joint angle at initial contact and maximum displacement during stance phase for both walking and running (3). Despite some conflicting evidence, altered kinematics may very well contribute to CAI.
In previously reported research on contributing mechanisms for CAI, only a small number of studies addressed ankle kinematics during gait, hence, making a general statement on CAI-related ankle kinematic adaptations difficult. Moreover, in previous studies, the foot was modeled as one rigid segment, thus ignoring the complexity of the ankle and foot anatomy and kinematics. Insight into foot function can be enhanced by the use of multisegmented foot models (30), which have proven useful in other patient populations, e.g., diabetic foot patients (32) and patients with rheumatoid arthritis (40). This approach may show kinematic patterns that a rigid foot would mask. Various studies have stated that foot characteristics may play a role in the mechanism of an ankle sprain, e.g., a higher mobility of the first ray or medial arch height (23,39). These findings call for more insight, not only into rear foot kinematics but also into the behavior of other foot segments during loading situations. At this moment, to the authors’ knowledge, no research has been conducted in patients with CAI using a multisegmented foot model.
Notwithstanding the relative high amount of patients who develop residual symptoms or CAI after an acute ankle sprain, some patients return to their preinjury level of functional participation without any negative impact after a sustained sprain. These “copers” somehow differ from subjects with CAI, and identifying these differences might help clarify the contributing mechanisms to CAI. Other studies already identified some dissimilarities between subjects with CAI, copers, and healthy controls, but further research is warranted (3,37).
The purpose of this study was primarily to compare ankle and foot kinematics during the stance phase of gait between healthy controls and subjects with CAI using both a rigid foot segment and the Ghent Foot Model (7), a validated multisegmented foot model. In addition, a third group of subjects with a recent ankle sprain, but without symptoms of CAI (copers), was included to evaluate possible kinematic adaptations and differences compared with the other groups. The rigid foot in this study was used to compare with literature, and in accordance with previous studies, a more inverted foot position and dorsiflexion reduction in subjects with CAI were hypothesized.
Twenty-nine subjects with CAI (15 males and 14 females, 10 ± 13 sprains annually, 5 ± 3 months to last sprain), 24 subjects with a recent ankle sprain (12 males and 12 females, 12 ± 5 months to last sprain), and 24 controls (10 males and 14 females) participated in this study. For the CAI group, all of the following inclusion criteria had to be met: 1) a history of at least one ankle sprain that resulted in pain, swelling, and stiffness, prohibiting participation in sport, recreational, or other activities for at least 3 wk; 2) repeated ankle sprains; 3) presence of giving way; 4) feeling of weakness around the ankle; and 5) a decreased functional participation (recreational, competitive, or professionally) as a result of the ankle sprains. The control group had no history of lower leg injury in the last 2 yr. The third group, the copers, consisted of subjects who had sustained an ankle sprain in the last 2 yr but were not experiencing ankle instability, as defined previously (criteria 2 to 5 were exclusion criteria). Overall exclusion criteria were ankle fracture or surgery, lower limb pain (not related to an ankle sprain), an ankle sprain in the last 3 months, and equilibrium deficits. All subjects were recreationally active, defined by at least 1.5 h of cardiovascular activity per week. Subject characteristics are shown in Table 1. The Ghent University Hospital ethics committee approved this study, and all subjects provided informed consent before participation.
Kinematic data were collected at 500 Hz on a 20-m-long instrumented runway with a six-camera optoelectronic system (OQUS 3, Qualysis). A force plate (500 Hz, Advanced Mechanical Technology, Inc., Watertown, MA) was built into the runway for synchronized event detection. In addition, a normal video camera (25 Hz, Sony) captured the test trials for a visual control record.
For each subject, anthropometric characteristics were registered and a questionnaire about the medical history was completed. Subjects also filled out the Foot and Ankle Disability Index (FADI) and its sport subscale (FADI-S) for baseline functionality assessment. The results of this assessment were not used as inclusion criteria but as a discriminative measure between groups (Table 1). Subjects were tested unilaterally. The most unstable ankle, based on the subject’s medical history, was analyzed in the CAI group. In the coper group, the side was selected depending on which ankle the subject had sprained in the last 2 yr. If the subject had sprained both ankles in the last 2 yr, the most recently sprained ankle was included in the study. In the control group, the foot chosen was randomized. Chi-square tests showed that there was no significant difference in the amount of dominant vs nondominant tested ankles between groups.
For capturing kinematic data, spherical reflective surface markers (7 mm) were placed using double-sided tape on anatomical landmarks of the foot and lower leg, along with tracking markers, according to the Ghent Foot Model (7). This six-segment model is defined by the shank, rear foot, midfoot, medial and lateral forefoot, and hallux (Fig. 1). Markers were placed by the same researcher for all subjects. First, a static measurement was recorded for 5 s to define the different segments of the Ghent Foot Model (GFM). During this measurement, the subject had to perform a tandem stand with the tested leg in front and the front knee slightly flexed so that the lower leg was perpendicular to the floor.
During the gait measurements, speed was monitored using a walk and jog laser (Astech LDM 42A, 50 Hz), which was pointed at the subject’s thorax. Subjects had to walk barefoot at a constant speed of 1.5 m·s−1 (1.4–1.6 m·s−1) while data were collected using a midgait protocol. During running, subjects had to maintain a constant speed of 3.5 m·s−1 (3.3–3.7 m·s−1). The starting position for running was 10 m before the force plate. Subjects were first allowed to familiarize themselves with the test procedure by performing a minimum of three practice trials. The actual test was repeated until three usable trials were captured. Trials were discarded if the speed was not in range, if two feet touched the force plate, or if subjects were seen to show an adaptation in stride length or frequency in an attempt to hit the force plate.
Kinematic data were processed by using Visual 3D (C-Motion, Germantown, MD). The dependent variables calculated for this study were the joint angles of the rigid food and the different segments of the GFM. Before joint angle calculation, marker coordinates were filtered using a fourth-order Butterworth low-pass filter at 10 Hz for walking and at 15 Hz for running, with 50 points reflected. Interjoint motion was calculated using Euler rotations (X–Y–Z) (7). Rotation around the X-, Y-, and Z-axis defined the plantarflexion/dorsiflexion (sagittal plane), inversion/eversion (frontal plane), and abduction/adduction (transversal plane) motion, respectively. The stance phase was determined using the vertical component of the ground reaction force with a threshold set at 10 N, and then each point in the time series was normalized to 100%. The rigid foot was defined by markers on the calcaneus, the lateral malleolus, and the head of the first and fifth metatarsal heads. The other segments were defined according to the multisegmented GFM (7). For each subject, the three trials per condition were averaged.
To compare between groups, a curve analysis was performed using statistical parametric mapping (SPM) (13). Initially, ANOVA over the normalized time series was used to establish the presence of any significant differences between the three groups. If statistical significance was reached, post hoc t-tests over the normalized time series were used to determine between which groups significant differences occurred. For both the ANOVA and t-test analyses, SPM involved four steps. The first was computing the value of a test statistic at each point in the normalized time series. The second was estimating temporal smoothness on the basis of the average temporal gradient. The third was computing the value of test statistic above which only α = 5% of the data would be expected to reach had the test statistic trajectory resulted from an equally smooth random process. The last was computing the probability that specific suprathreshold regions could have resulted from an equivalently smooth random process. Technical details are provided elsewhere (13,27).
Overall, rotations in the frontal plane representing inversion/eversion showed significant ANOVA results (P < 0.05) for the rigid foot, the rear foot, the midfoot, and the medial forefoot during midstance and late stance. Furthermore, ANOVA results (P < 0.05) indicated differences in rotations in the sagittal and transversal plane for the rear foot during walking. Post hoc analysis results are presented below and showed similar findings for both the CAI and coper group compared with the control group. No differences were found for plantarflexion/dorsiflexion and abduction/adduction angles for both running and walking data in the post hoc analysis.
Foot (rigid foot in relation to the shank)
Walking analysis showed a significantly greater eversion angle in the CAI group, from 11% to 73% of the stance phase (average difference of 2.17°, P < 0.001), and in the coper group, from 19% to 73%, compared with that in the control group (average difference of 2.19°, P < 0.001). During the significant period of this midstance phase, the foot first progressed toward a maximally everted position and then subsequently inverted toward the end of this phase (Fig. 2). No significant differences were found for the running data.
Rear foot (in relation to the shank)
The running trials exhibited a significantly greater eversion of the rear foot in the CAI group, from 56% to 73% of the stance phase (average difference of 2.72°, P = 0.045), and in the coper group, from 29% to 86% (average difference of 3.47°, P = 0.001), compared with controls. The rear foot reached a maximally everted position in the beginning of the midstance and then slowly supinated, during the period with significant differences, toward toe off (Fig. 3). No significant differences were found for the walking data.
Midfoot (in relation to the rear foot)
No significant between-group differences for walking and running trials were found.
Lateral forefoot (in relation to the midfoot)
No significant between-group differences for walking and running trials were found.
Medial forefoot (in relation to the midfoot)
For both walking and running, the CAI group showed significantly more inversion compared with the control group from 87% to 98% of stance phase (average difference of 9.42°, P = 0.031) during walking and from 56% to 91% (average difference of 9.81°, P < 0.001) during running. During this significant period, the medial forefoot everted until maximal before supinating at the end of stance phase. The coper group showed significantly more inversion compared with the control group from 10% to 83% of the stance phase in walking (average difference of 7.42°, P = 0.007) and from 28% to 30% of the stance phase in running (average difference of 8.28°, P = 0.049) (Figs. 4 and 5). The medial forefoot first supinated to a maximally supinated position in this period and then started to evert toward the end of midstance (only significant for the walking condition).
Hallux (medial forefoot–hallux)
No significant between-group differences for walking and running trials were found.
To our knowledge, this was the first study that used a multisegmented foot model to describe gait kinematics in subjects with CAI. The aim was to explore kinematic differences on the basis of the rigid foot and Ghent Foot Model (7) between the three study groups. Moreover, SPM allowed us to compare groups throughout the stance phase, alleviating a priori assumptions about when in the stance phase, statistical differences might occur (27). In general, similar differences were found between the CAI and coper group compared with the control group. Our results show no significant kinematic differences in the early stance phase, which was not expected on the basis of literature (6,22,24). We did identify differences in the midstance and late stance, which could possibly be linked to the mechanism of CAI.
Ankle kinematics based on the rigid foot model indicated a more everted foot for both the CAI and the coper group compared with the control group. The difference was significant from approximately 10% and 20%, respectively, to 70% of stance during walking, with no significant difference for the remainder of stance. Our results deviate from findings in literature indicating a more inverted foot position at and just after heel strike (6,24) or during the whole stance phase (11). In the study of Delahunt et al. (6), a more in verted foot position was also found before heel strike. However, our study only analyzed the stance phase and disregarded the swing phase of the gait cycle. Previous data on kinematics throughout the stance phase to compare results with are scarce. The more everted position of the foot in subjects with a history of ankle sprains found in our study does not seem to fit with the pathomechanics of an ankle sprain. Nevertheless, a prospective study by Willems et al. (38) on gait-related risk factors for ankle sprains found an increased medial loading of the foot and a trend of higher eversion excursion in subjects susceptible to an ankle sprain. They suggested that an unstable feeling might result in a more medial foot roll-off as a compensation for possible ankle sprains. This compensation mechanism might also cause the higher foot eversion found in the current study. A recent study on evertor and invertor muscle strength in patients with CAI might provide an alternative hypothesis on the more everted foot position (4). These authors found an overall decrease in muscle strength and a significantly higher concentric evertor to eccentric invertor torque ratio in subjects with CAI (4) This imbalanced ratio may result in an inadequate eccentric control of eversion during gait. In comparison, a study by Rabbito et al. (29) found a greater eversion during walking related to a posterior tibial tendon dysfunction. These results might also explain the more everted foot position found here, but further research is necessary to be able to identify the precise underlying mechanism. Furthermore, our results showed no decreased dorsiflexion for the CAI group during stance phase (10). In general, for the rigid foot kinematics, the current study does not confirm the postulated hypotheses of more inversion and dorsiflexion in gait in subjects with CAI.
In their review on foot characteristics in relation to ankle sprains, Morrison and Kaminski (25) emphasized the possible midfoot and forefoot involvement. They underlined the importance of capturing foot motion to be able to understand lower extremity mechanics and foot-related risk factors for a lateral ankle sprain. In the past, studies using static measurements have identified, e.g., a lower medial arch and a greater metatarsophalangeal joint extension as possible risk factors for a lateral ankle sprain (23,39). However, to date, no kinematic evaluation has been made using a multisegmented model to compare motions at midfoot and forefoot joints during a functional movement in ankle sprainers. In our study, multisegmented ankle and foot kinematics based on GFM demonstrated several between-group differences. The rear foot was more everted during midstance of running for both the CAI and coper group in comparison with the control group. In addition, the medial forefoot defined by the first ray showed a more inverted position in midstance and late stance for both walking and running. A possible explanation for this phenomenon may be found in the function of the peroneus longus (PL), which everts the first ray during the stance phase of gait. The PL is also believed to exert a stabilizing influence on the first ray (19). Because in this study, a more inverted first ray is found in subjects with CAI, we assume the normal function of PL could be impaired in these subjects, which is in line with the study of Santilli et al. (31) who found a decreased activity of the PL during stance phase in subjects with functional instability. Furthermore, the PL is found to be active in midstance and late stance of a gait cycle (18), which corresponds with the timing of the observed kinematic differences for the medial forefoot. In addition, another possible explanation might be found in the biomechanical coupling of rear foot and forefoot motion, where a pronation motion of the rear foot, as seen here, is associated with a supination motion of the forefoot to be able to maintain full ground contact (35). This inverted position of the first ray results in a so-called loosely packed position, which reflects a mechanically less stable condition (28). Plantar pressure data also indicated a more laterally deviated pressure displacement in forefoot during the late stance phase as a risk factor for ankle sprains phase (38). Maybe the less stable position of the first ray, found in this study, might explain these plantar pressure results. Therefore, medial forefoot kinematics may play a role in the mechanism of CAI.
The results of this study indicated differences in the midstance and late stance phase of a gait cycle and not in the initial postimpact phase after heel strike. This might not be expected, because it is generally considered that ankle sprains occur in the initial loading response phase. However, the exact timing of the ankle sprain mechanism in a heel to toe foot roll-off during gait conditions, based on real ankle sprain events, has not been determined yet because of ethical considerations. Some authors have pointed out that other possible time frames might also be important during a gait cycle. Stormont et al. (33) indicated that ankle instability may occur during both loading and unloading transitions. Furthermore, Konradsen and Voigt (21) demonstrated, on the basis of a cadaver study, that the ankle and foot will be able to stabilize itself and move into normal eversion at the beginning of the stance phase even though it is set to the ground with a substantial degree of malalignment. They therefore concluded that sustaining an ankle sprain due to preimpact unintentional malalignment of the ankle seems improbable (21). Other studies on plantar pressure data also indicated deviations during midstance in relation to CAI (26) and late stance as a risk factor for ankle sprains (38). The midstance and late stance findings in our study contribute to the concept of other possible important time frames in the mechanism of ankle injuries during gait. Moreover, findings in these time frames may very well be relevant because a lot of ankle sprains happen during jump landing activities in which the forefoot is the first part of the foot to touch the ground surface in a toe to heel foot roll-off. Further research on multisegmented landing kinematics is therefore warranted.
In this study, three different groups were defined. For the instability group, only subjects with functional ankle instability were selected on the basis of the described inclusion criteria. For the coper group, subjects with a recent ankle sprain were chosen because they are more susceptible for resprain (17). For some reason, these subjects had not developed a chronic condition as of yet and therefore were interesting to consider as a separate group. It is therefore noteworthy that no kinematic differences were found between the CAI group and the coper group. This means that our coper group had the same kinematic adaptations after sustaining a recent ankle sprain as the group with a chronically unstable ankle. The FADI and FADI-S on the contrary clearly discriminated between these groups regarding subjective ankle complaints (12). A possible explanation may be found in other influencing factors such as proprioception, postural stability, strength, or neuromuscular control (15,17). Further research is necessary to elucidate the underlying differentiating mechanisms that define a coper and that differentiate between copers and subjects with CAI.
Although we feel that the results of the present study are promising, there are some methodological limitations to bear in mind. Both walking and running occurred barefooted. Mechanical differences have been demonstrated between barefoot and shod locomotion (9); in particular, increased ankle plantarflexion and reduced eversion were reported in barefoot running compared with shod running (8). Although barefoot running may not be completely representative of normal shod conditions, alternatives are not always obvious when using a multisegmented model. Group definitions used in this study may differ from other studies, making comparison difficult. The coper group used in our study had to have had a relatively recent ankle sprain. Other studies have used the term copers for everyone who ever sprained their ankle but who did not develop CAI (2,3). However, possible coping strategies in the acute phase may not be present or may be different several years after sustaining an ankle sprain. Moreover, kinematics of someone who sprained their ankle some years ago may not be representative of their kinematics at that moment. Therefore, we chose copers with a recent sprain for our study. For data collection, we only looked at the stance phase and, therefore, maybe missed important information on approach kinematics (6,22,24). This was due to a technical limitation of our capturing volume and should be further addressed in future research. Furthermore, we did not normalize data against a reference value, so as not to eliminate inherent variations in foot morphology from our data. One might possibly argue that foot morphology may differ between groups and should be excluded from actual kinematics. Future research should also address multisegment foot kinematics in more provocative situations, such as drop landings or side cutting maneuvers, which may also show altered foot and ankle kinematics in subjects with CAI.
This study indicates possible benefits of using a multisegmented foot model in the search for contributing factors in the mechanism of CAI during the stance phase of gait. During midstance, we found a more everted position of the rigid foot during walking and of the rear foot during running. In addition, we found a more inverted position for the medial forefoot in both the CAI and coper group compared with the control group during midstance and late stance, possibly reflecting a mechanically less stable position. These results warrant further research to expand the knowledge regarding foot kinematics in subjects with CAI.
The authors would like to thank Tanneke Palmans for her help in data processing for this study.
The authors report no conflict of interest.
No funding was received for this study, and the results of the present study do not constitute endorsement by the American College of Sports Medicine.
1. Anandacoomarasamy A, Barnsley L. Long term outcomes of inversion ankle injuries. Br J Sports Med
. 2005; 39: e14.
2. Brown C. Foot clearance in walking and running in individuals with ankle instability. Am J Sports Med
. 2011; 39: 1769–76.
3. Brown C, Padua D, Marshall SW, Guskiewicz K. Individuals with mechanical ankle instability exhibit different motion patterns than those with functional ankle instability and ankle sprain copers. Clin Biomech (Bristol, Avon)
. 2008; 23: 822–31.
4. David P, Halimi M, Mora I, Doutrellot PL, Petitjean M. Isokinetic testing of evertor and invertor muscles in patients with chronic ankle instability
. J Appl Biomech
. In press.
5. Delahunt E, Coughlan GF, Caulfield B, Nightingale EJ, Lin CW, Hiller CE. Inclusion criteria when investigating insufficiencies in chronic ankle instability
. Med Sci Sports Exerc
. 2010; 42 (11): 2106–21.
6. Delahunt E, Monaghan K, Caulfield B. Altered neuromuscular control and ankle joint kinematics during walking in subjects with functional instability of the ankle joint. Am J Sports Med
. 2006; 34: 1970–6.
7. De Mits S, Segers V, Woodburn J, Elewaut D, De CD, Roosen P. A clinically applicable six-segmented foot model. J Orthop Res
. 2012; 30 (4): 655–61.
8. De Wit B, De Clercq D, Aerts P. Biomechanical analysis of the stance phase during barefoot and shod running. J Biomech
. 2000; 33 (3): 269–78.
9. Divert C, Mornieux G, Baur H, Mayer F, Belli A. Mechanical comparison of barefoot and shod running. Int J Sports Med
. 2005; 26: 593–8.
10. Drewes LK, McKeon PO, Kerrigan DC, Hertel J. Dorsiflexion deficit during jogging with chronic ankle instability
. J Sci Med Sport
. 2009; 12: 685–7.
11. Drewes LK, McKeon PO, Paolini G, et al. Altered ankle kinematics and shank-rear-foot coupling in those with chronic ankle instability
. J Sport Rehabil
. 2009; 18: 375–88.
12. Eechaute C, Vaes P, Van AL, Asman S, Duquet W. The clinimetric qualities of patient-assessed instruments for measuring chronic ankle instability
: a systematic review. BMC Musculoskelet Disord
. 2007; 8: 6.
13. Friston, K, Ashburner J, Kiebel S, et al., Eds. Statistical Parametric Mapping: The Analysis of Functional Brain Images
. London, United Kingdom: Elsevier; 2011, 656 pp.
14. Hertel J. Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability. J Athl Train
. 2002; 37: 364–75.
15. Hiller CE, Nightingale EJ, Lin CW, Coughlan GF, Caulfield B, Delahunt E. Characteristics of people with recurrent ankle sprains: a systematic review with meta-analysis. Br J Sports Med
. 2011; 45: 660–72.
16. Hootman JM, Dick R, Agel J. Epidemiology of collegiate injuries for 15 sports: summary and recommendations for injury prevention initiatives. J Athl Train
. 2007; 42: 311–9.
17. Hubbard TJ, Kramer LC, Denegar CR, Hertel J. Contributing factors to chronic ankle instability
. Foot Ankle Int
. 2007; 28: 343–54.
18. Hunt AE, Smith RM, Torode M. Extrinsic muscle activity, foot motion and ankle joint moments during the stance phase of walking. Foot Ankle Int
. 2001; 22: 31–41.
19. Johnson CH, Christensen JC. Biomechanics of the first ray. Part I, The effects of peroneus longus function: a three-dimensional kinematic study on a cadaver model. J Foot Ankle Surg
. 1999; 38: 313–21.
20. Konradsen L, Bech L, Ehrenbjerg M, Nickelsen T. Seven years follow-up after ankle inversion trauma. Scand J Med Sci Sports
. 2002; 12: 129–35.
21. Konradsen L, Voigt M. Inversion injury biomechanics in functional ankle instability: a cadaver study of simulated gait. Scand J Med Sci Sports
. 2002; 12: 329–36.
22. Lin CF, Chen CY, Lin CW. Dynamic ankle control in athletes with ankle instability during sports maneuvers. Am J Sports Med
. 2011; 39: 2007–15.
23. Mei-Dan O, Kahn G, Zeev A, et al. The medial longitudinal arch as a possible risk factor for ankle sprains: a prospective study in 83 female infantry recruits. Foot Ankle Int
. 2005; 26: 180–3.
24. Monaghan K, Delahunt E, Caulfield B. Ankle function during gait in patients with chronic ankle instability
compared to controls. Clin Biomech (Bristol, Avon)
. 2006; 21: 168–74.
25. Morrison KE, Kaminski TW. Foot characteristics in association with inversion ankle injury. J Athl Train
. 2007; 42: 135–42.
26. Nawata K, Nishihara S, Hayashi I, Teshima R. Plantar pressure distribution during gait in athletes with functional instability of the ankle joint: preliminary report. J Orthop Sci
. 2005; 10: 298–301.
27. Pataky TC. Generalized n
-dimensional biomechanical field analysis using statistical parametric mapping. J Biomech
. 2010; 43: 1976–82.
28. Perez HR, Reber LK, Christensen JC. The effect of frontal plane position on first ray motion: forefoot locking mechanism. Foot Ankle Int
. 2008; 29: 72–6.
29. Rabbito M, Pohl MB, Humble N, Ferber R. Biomechanical and clinical factors related to stage I posterior tibial tendon dysfunction. J Orthop Sports Phys Ther
. 2011; 41: 776–84.
30. Rankine L, Long J, Canseco K, Harris GF. Multisegmental foot modeling: a review. Crit Rev Biomed Eng
. 2008; 36: 127–81.
31. Santilli V, Frascarelli MA, Paoloni M, et al. Peroneus longus muscle activation pattern during gait cycle in athletes affected by functional ankle instability: a surface electromyographic study. Am J Sports Med
. 2005; 33: 1183–7.
32. Sawacha Z, Cristoferi G, Guarneri G, et al. Characterizing multisegment foot kinematics during gait in diabetic foot patients. J Neuroeng Rehabil
. 2009; 6: 37.
33. Stormont DM, Morrey BF, An KN, Cass JR. Stability of the loaded ankle. Relation between articular restraint and primary and secondary static restraints. Am J Sports Med
. 1985; 13: 295–300.
34. Valderrabano V, Hintermann B, Horisberger M, Fung TS. Ligamentous posttraumatic ankle osteoarthritis. Am J Sports Med
. 2006; 34: 612–20.
35. Valmassy R. Clinical Biomechanics of the Lower Extremities
. Maryland Heights, MO:Mosby; 2012. p. 19–21.
36. van Rijn RM, van Os AG, Bernsen RM, Luijsterburg PA, Koes BW, Bierma-Zeinstra SM. What is the clinical course of acute ankle sprains? A systematic literature review. Am J Med
. 2008; 121: 324–31.
37. Wikstrom EA, Tillman MD, Chmielewski TL, Cauraugh JH, Naugle KE, Borsa PA. Discriminating between copers and people with chronic ankle instability
. J Athl Train
. 2012; 47: 136–42.
38. Willems T, Witvrouw E, Delbaere K, De Cock A, De Clercq D. Relationship between gait biomechanics and inversion sprains: a prospective study of risk factors. Gait Posture
. 2005; 21: 379–87.
39. Willems TM, Witvrouw E, Delbaere K, Philippaerts R, De Bourdeauhuij I, De Clercq D. Intrinsic risk factors for inversion ankle sprains in females—a prospective study. Scand J Med Sci Sports
. 2005; 15: 336–45.
40. Woodburn J, Nelson KM, Siegel KL, Kepple TM, Gerber LH. Multisegment foot motion during gait: proof of concept in rheumatoid arthritis. J Rheumatol
. 2004; 31: 1918–27.
Keywords:© 2013 American College of Sports Medicine
3-D KINEMATICS; CHRONIC ANKLE INSTABILITY; CURVE ANALYSIS; REAR FOOT; MEDIAL FOREFOOT