Influence of Turnout on Foot Posture and Its Relationship to Overuse Musculoskeletal Injury in Professional Contemporary Dancers. A Preliminary Investigation

Abstract

Background: The angle of turnout is thought to predispose professional dancers to overuse musculoskeletal injuries of the lower limb; yet, the influence of angle of turnout on foot posture is currently unknown. Methods: Twelve professional contemporary dancers (five women and seven men; mean age, 26.8 years) were recruited. The angle of gait and angle of turnout were measured using a quasi-static clinical tracing method. Foot posture was assessed in the base of gait and angle of turnout using the Foot Posture Index. Each dancer completed a dance history and injury questionnaire. Results: The results show a tendency toward a pronated foot posture (mean, 9°) in the angle of turnout position. A significant relationship was noted between the Foot Posture Index and angle of turnout (ρ = 0.933–0.968, P < .01) and between the number of reported injuries and change in foot posture in the angle of turnout (ρ = 0.789, P < .01) (right foot only). Twenty-eight injuries were reported; male dancers experienced a mean of 2.8 injuries and females a mean of 1.6 injuries. An inverse relationship was noted between age at training initiation and total reported injuries (r =−0.867, P < .01). All of the dancers reported a history of injury to the spine or lower limb, and 9 of the 12 reported an injury within the previous 12 months. Conclusions: Turnout is one of the most fundamental aspects of dance technique. This study suggests a trend toward pronation in angle of turnout and a link to lower-limb musculoskeletal injury.

Professional dancers are required to be skilled artists, athletes, and gymnasts to survive the highly competitive nature of the dance industry. [1,2] There are numerous dance styles, such as contemporary, jazz, and tap; however, classical ballet is frequently taught as the core style because it encourages fundamental principles that promote stability and strength with aesthetic appeal. [3,4] Literature relating to modern and contemporary dancers, however, has received limited attention. [5] Movement patterns performed in many dance styles use extreme ranges of motion that alter the biomechanics of the lower kinetic chain. These patterns of extreme positions can be perceived as “abnormal” and can place bones, muscles, tendons, ligaments, and nerves under strain, which may lead to acute or chronic injury. [3,6–8] Epidemiologic studies [1,2,4,6–8,9] report a lifetime injury incidence of 90% in dancers, with approximately 75% of all injuries occurring in the lower limbs. Forty percent of these injuries are linked to the foot, ankle, and lower leg. [5,9,10] Moreover, overuse injuries account for most dance injuries, with some individuals seeming more susceptible than others. [11,12]

The aesthetic appeal of dance is rooted in the quality of sequential movement and is not simply a series of static positions. During the 17th century, the standard turnout position, with the feet placed heel to heel, was angled at 90°. Over the years, this position has increased to 180° because it improves aesthetic appeal and augments triplanar range of motion of the lower limb. There are various opinions about how this position should ideally be achieved. Studies by Coplan [13] and Gilbert et al [14] suggest that a 180° turnout should be accomplished by externally rotating the hips 140° and the tibia 10°. The remaining 30° of external rotation should come from the feet. Hamilton et al [15] noted that many of the dancers performed a demi-plié before extending the knees to assume the turned out first position. This movement, in effect, anchors the feet to the supporting surface, allowing compensatory motions to occur at the subtalar and midtarsal joints to achieve a greater angle of turnout. Kravitz and Murgia [16] support the concept that turnout should ideally be accomplished solely through hip external rotation, maintaining the sequential alignment of the hip, knee, and foot. Dancers are generally taught to assume the turnout position by externally rotating their hips and maintaining the alignment among the hip, knee, and foot. Nonetheless, the competitive environment can push dancers to strive for perfection, and individuals may try to achieve a greater turnout by rotating distally from the feet up rather than proximally from the hips down. [9]

Many individuals cannot achieve the aesthetic ideal of 180° of turnout and force the position by abducting the feet further than the available hip external rotation. This movement can lead to excess pronation, external tibial torsion, valgus knee stress, an increased Q angle, and lumbar lordosis. [9,11] Coplan [13] commented that a forced turnout beyond the available hip range of motion is potentially the most serious training error in dance and can be considered a common flaw in technique. It is, therefore, perceived that measures of functional turnout are more relevant than hip external rotation to the prevalence of nontraumatic injuries and that first position serves as a useful guide for functional turnout. Increasing subtalar joint pronation increases forefoot abduction, thus promoting the visual illusion of an increased turnout position. Nevertheless, the compensatory adjustments to this position in the lower limb have been associated with the development of a variety of overuse abnormalities commonly found in classical dancers, including tibialis posterior tendinopathy, hallux valgus, plantar fasciitis, and stress fractures. [10,17]

Professional dancers have a highly developed kinesthetic awareness as a result of their repetitive training regimens. This can assist in a dancer’s rehabilitation, especially if overuse injuries are associated with a poor dance technique. [16] This characteristic, combined with a willingness to comply with treatment to achieve longevity in their career, makes these individuals a particularly interesting and challenging patient group. Turnout is a fundamental factor in many dance techniques and is frequently the start or end position of forceful and explosive movement patterns, such as jumps. Its influence as a contributing factor in the development of overuse injuries warrants investigation. Although the literature [1,3–6,10,11,16,18,19] suggests that changes in foot posture and repetitive training schedules may be associated with lower-limb overuse injury in dancers, the proposed relationship requires further exploration. The aim of this study, therefore, was to investigate the effect of turnout on foot posture and its association with overuse musculoskeletal injury in professional contemporary dancers.

Methods

Sample and Materials

Twelve contemporary dancers (five women and seven men) with a mean ± SD age of 26.8 ± 3.9 years (range, 21–36 years) were recruited from two leading professional dance companies in the United Kingdom (n =6 from each company). The number of individuals able to participate in the study was limited by their rigorous training and touring schedules. Each participant met the following inclusion criteria: aged 20 to 40 years; a current traumatic injury that renders him or her unable to assume a functional turnout position; a minimum of 3 years of professional contemporary and ballet dance training; and a minimum of 1 year as a professional contemporary dancer. Ethical approval for the proposed study was provided by the Cardiff School of Health Sciences Ethics Panel, Cardiff Metropolitan University, Cardiff, United Kingdom.

Three assessment tools were used in this study: a clinical tracing of the foot, the Foot Posture Index (version 6), and a dance background/injury questionnaire. The clinical tracing tool involved the quasi-static method for measurement of angle of gait and angle of turnout. [20] Base of gait was not a necessary assessment criterion but was used as a position reference point. This method permits the angle of each foot in base of gait and turnout to be measured through bisection of the heel to the forefoot measured against the line of progression (Fig. 1). The Foot Posture Index was used to classify foot posture. This measurement tool recognizes the multisegmented nature of the foot and uses a series of scores based on the Likert scale, with reference values ranging from −12 (severely supinated) to 12 (severely pronated). The reliability and validity of the Foot Posture Index has been previously established. [21–24] A written questionnaire specifying demographic details, information on dance background, and injury history was also devised. Weight and height data were omitted from the questionnaire because it has been reported [13] that dancers, in general, desire a lower body weight and the criteria were of no statistical significance to this particular study.

Figure 1. Bisections used to calculate angle of turnout. The horizontal line drawn along the back of both heels enables the perpendicular vertical line of progression to be drawn, from which the turnout angles are calculated for each foot.

Figure 1. Bisections used to calculate angle of turnout. The horizontal line drawn along the back of both heels enables the perpendicular vertical line of progression to be drawn, from which the turnout angles are calculated for each foot.

Procedure

All of the measurements were recorded three times and were undertaken by the same investigator (S.N.C.). Before data collection, each dancer was required to perform a daily warm-up. The protocol was as follows: The participant was asked to march on the spot behind the paper and was timed for 20 sec. He or she was then instructed to step onto the paper, and this was considered the base of gait position. Each dancer was instructed to avoid movement and to look straight ahead (Fig. 2A). With a black ballpoint pen, the investigator traced around both feet, keeping the pen vertical and snug to the feet. The Foot Posture Index was determined in this position, and the dancer was then instructed to turnout and perform a demi-plié (Fig. 2B) before extending the knees to adopt the functional turnout position (Fig. 2C). The demi-plié was included in the study because Hamilton et al [15] considered it a natural variant and a common method for the dancer to check that he or she is in the functional turnout position. Its incorporation, therefore, standardized the functional element of the turnout position. The dancers were again asked to avoid movement and to look straight ahead. A blue ballpoint pen was then used to trace around the dancer’s feet, keeping it vertical and snug to the feet as before. The Foot Posture Index was then determined in this position. The dancer was then asked to step forward off the paper. Once the data had been collected, the dancers were instructed to complete the questionnaire.

Figure 2. Turnout procedure. A, Base of gait position; B, a demi-plié in turnout is performed; C, followed by knee extension to the functional turnout position. The feet were traced in this position.

Figure 2. Turnout procedure. A, Base of gait position; B, a demi-plié in turnout is performed; C, followed by knee extension to the functional turnout position. The feet were traced in this position.

Before data collection, intrarater reliability of the quasi-static clinical tracing and the Foot Posture Index was established. Data were collected on five healthy individuals (three women and two men; mean ± SD age, 30.0 ± 1.9 years; range 26–37 years) on two separate occasions 1 week apart. Intraclass correlation coefficients (2,k) demonstrated acceptable reliability, with a range of 0.652 to 0.990 for the angle of turnout, angle of gait, base of gait, and Foot Posture Index.

Statistical Analysis

A commercially available software program (SPSS version 15 for Windows; SPSS Inc, Chicago, Illinois) was used for data analysis. All of the data were initially visually checked for outliers. Descriptive statistics were compiled for the main study population relating to dance history and injury history, along with a graphical representation of Foot Posture Index scores in base of gait and turnout. The data for the left and right feet were not pooled, which, therefore, respects the assumption of independence. [25] Because the data for the Foot Posture Index were measured on an ordinal scale, a nonparametric Spearman ρ correlation was used to establish associations among base of gait, angle of turnout, number of reported injuries, and the Foot Posture Index. A Pearson r correlation coefficient was used for the parametric data, [26] which determined whether associations occurred between age at dance training commencement, number of reported injuries, angle of gait, and angle of turnout. A significance of P < .05 was used for all of the statistical analyses.

Table 1. Dance Experience of the 12 Study Participants

Table 1. Dance Experience of the 12 Study Participants

Results

Dance Background

Twelve dancers, six from each company, were finally recruited to the study. There were five female and seven male dancers. The descriptive statistics relating to their dance experience are displayed in Table 1. The ranges are quite broad, particularly relating to the age that the dancers started dancing. The mean ± SD age at which the women started dancing was 4 ± 1 years compared with 11.4 ± 5.3 years for the men.

Injuries

Twenty-eight injuries were reported among the dancers, with a mode frequency value of two injuries to the spine or lower limb per participant. The male dancers experienced a mean ± SD of 2.86 ± 1.77 injuries; the female dancers had a mean ± SD of 1.6 ± 0.55 injuries. Eleven of the injuries reported occurred in the past 12 months. Figure 3 illustrates the locations of the reported injuries, identifying the period when they occurred. The dancers did not identify any lower-leg injuries. Sex differences were noted among the dancers, with men showing a preponderance versus women for injuries to the spine (4 versus 1), thigh (1 versus 0), knee (4 versus 2), ankle (4 versus 1), and foot (3 versus 1). There was an equal distribution for injuries to the hip (3 versus 3).

Figure 3. Locations of the reported injuries to the spine and lower limb.

Figure 3. Locations of the reported injuries to the spine and lower limb.

Angle of Gait, Angle of Turnout, and Foot Posture

The mean angle of gait was 9.1° and 8.1° for the left and right feet, respectively. The mean angle of turnout for the left foot (56.4°) was 4.7° lower than that for the right foot (61.1°) (Table 2). The Foot Posture Index values showed that most of the dancers’ feet were categorized as “neutral” when they stood in base of gait (Fig. 4). As each dancer assumed the turnout position, there was a distinct tendency toward pronation (Fig. 5). There was no significant relationship (P < .05) between angle of gait and angle of turnout as interpreted with the Spearman rank correlation coefficient. This finding was also noted between the left and right foot angle of gait and angle of turnout (P < .05). A variety of significant relationships (P < .05, P < .01), however, were noted between these variables, which ranged from r = 0.635 to r = 0.968 (Table 3). A negative relationship between the age the dancers started their professional training and the number of injuries was identified using the Pearson correlation coefficient (r =−0.867, P < .01).

Table 2. Mean Values for Angle of Gait (AOG) and Angle of Turnout (AOT)

Table 2. Mean Values for Angle of Gait (AOG) and Angle of Turnout (AOT)

Figure 4. Foot Posture Index scores in base of gait.

Figure 4. Foot Posture Index scores in base of gait.

Discussion

The purpose of this study was to investigate the effect of turnout on foot posture and its association with injury in professional contemporary dancers through investigation of the relationship between dance and injury. The approach focused on two key assumptions. First, a standing, weightbearing position was selected because it provides information about the functional closed kinetic relationship of the lower limb, including the foot. [27] Moreover, inclusion of the demi-plié provided a natural and realistic maneuver used to attain angle of turnout. Second, although foot position provides evidence of how it may affect alignment of the limb, it also supports the need for standardization. This is an important factor in the consideration of clinical measures in general and in optimizing operator error and reliability specifically.

Figure 5. Foot Posture Index scores in angle of turnout. Note the obvious change to a position beyond 5.

Figure 5. Foot Posture Index scores in angle of turnout. Note the obvious change to a position beyond 5.

Previous studies that have investigated turnout have concentrated predominantly on female classical ballet dancers undergoing their professional training. This study differs because it is more representative of the professional contemporary dancer and with more balanced numbers of male and female dancers (seven and five, respectively). The demographic statistics illustrate the varied dance experience in a small sample of professional dancers. Of particular interest is the trend relating to the sex of the dancer. The mean ± SD age at which the women started dancing was 4 ± 1 years. This was in contrast to male dancers, who had a mean ± SD start age of 11 ± 5 years. These values are slightly lower than those of Weiss et al, [1] who showed that women started to dance at a mean ± SD age of 6.5 ± 4.2 years and men at 15.6 ± 6.2 years. However, for this study, it could be anticipated that individuals who have been dancing from an earlier age may have accumulated more injuries attributable to the increased duration of dance participation. Contrary to this expectation were the findings that demonstrated an inverse relationship between age at training commencement and total reported injuries. This finding indicates that dancers who started their training at an earlier age accrued fewer injuries. This point is further illustrated by the fact that the male dancers accounted for 71% of the injuries, although this is likely to be affected by the slightly uneven male-to-female ratio. Nonetheless, the male dancers started their training later and experienced more injuries on an individual basis.

Table 3. Relationships Between Foot Posture Index (FPI), Angle of Gait (AOG), and Turnout.

Table 3. Relationships Between Foot Posture Index (FPI), Angle of Gait (AOG), and Turnout.

It could be argued that training from a young age promotes skeletal modeling of the individual in line with the activity, which shares similarities to the findings of Hamilton et al. [15] Therefore, continued training in the turnout position enables adaptive physiologic changes (ie, osseous and soft-tissue structures) to develop according to the demands of dance. In contrast, individuals who commence their training later may have a soft-tissue and skeletal structure that is not adapted to dance and turnout, yet they are required to participate at the same level. [3,4] Adaptations to technique to enhance aesthetic appeal, such as turnout beyond the natural range of hip rotation, increases the demands on the supporting structures in the closed kinetic chain. Further investigation into this area with a larger sample size is duly indicated.

The Foot Posture Index findings showed that most of the dancers had a neutral foot posture in base of gait, but there was a marked tendency toward pronation when they moved into turnout (Fig. 5 and Fig. 5). Excessive subtalar joint pronation is associated with increased strain on the medial longitudinal arch, the plantar fascia, and the plantar musculature of the foot. It is also linked as an etiologic factor in the development of abnormalities such as posterior tibial tendinopathy and hallux abducto valgus, which are common foot disorders found in dancers. Each dancer in this study had experienced at least one injury, which is greater than the 90% lifetime incidence reported by Thomas and Tarr [5] and Macintyre and Joy. [9] The hip and knee were the most commonly affected areas, although the combined scores for the foot and ankle represent 39% of the lower-limb injuries, which is in line with the 40% reported by Macintyre and Joy. [9] Although a small bias toward men in the sample of this study is duly noted, it was observed that compared with females, male dancers experienced more injuries to all areas except the hip, which showed an equal distribution. The spinal injuries could be related to lifting, which male dancers naturally do more than female dancers in contemporary dance and ballet. [5,6,16,28] Note that despite the considerable number of foot and ankle injuries experienced, none of the dancers had sought podiatric medical treatment.

The effects of subtalar joint pronation at the ankle, knee, hips, and spine are important when considering the frequent locality of the reported injuries. Excessive pronation causes internal tibial rotation, genu valgus, combined with muscular imbalance of the quadriceps due to an increased Q angle. Malalignment of the patella tendon, tightening of the iliotibial band, and increased lumbar lordosis, which increases the strain on the lumbar spine, can also occur. [19] Pronation increases the demands on these structures during walking and running; therefore, it is important to consider how these effects are compounded in an individual dancing at a professional level, where impact and participation levels are extremely high. The findings in this study indicate that a relationship existed between the number of reported injuries and the change in foot posture from base of gait to turnout for the right foot. Although the left foot did not reveal the same significant associations, there were strong relationships between the right and left feet. The results infer that the greater the change in foot posture from base of gait to turnout, the greater the risk of injury. Therefore, there are grounds to reject the null hypothesis; however, further research is necessary, especially because the relationship was not significant for both feet. These observations are supported by other studies [1,2,5,9–11,16] that have reported injury trends in male and female ballet dancers. Miller et al, [29] in particular, reported that male ballet dancers experienced knee pain and suggested that a lack of external rotation at the hip placed greater stress on the medial aspect of the knee. This can be further supported by the “lag concept” used to describe the absorption of limb rotation by the muscles, ligaments, and tendons of the knee. [30]

No relationship was found between Foot Posture Index scores in turnout and angle of turnout. Therefore, despite the trend toward pronation with turnout, the amount of change in foot posture did not seem to be significantly related to the angle of turnout, and the null hypothesis could be supported. Nevertheless, a significant relationship was identified between the number of injuries and the difference between angle of gait and angle of turnout for the right foot. This finding indicates that the greater the turnout from the natural base of gait, the greater the likelihood of overuse injury. Note that the results are significant only for the right foot, and it may be useful to consider the impact of additional variables, such as limb dominance, in future studies. This was an observation also noted by Gupta et al [3] in terms of hip strength and range of external rotation.

The results demonstrate a relationship between number of injuries and change in foot posture that accompanies turnout. The trend toward pronation and the high lower-limb injury rate in this demographic group is of clinical significance to podiatric physicians. Professional dancers are a potentially challenging patient group because the nature of the profession makes it difficult to accommodate the orthoses and modifications to footwear that are frequently prescribed to control excessive pronation. Contemporary dancers often dance barefoot, although ballet shoes and split-soled jazz shoes may also be worn. This study provides information on the relationship between turnout and injury to enable practitioners to adapt the treatment plan to their patients. The assessment procedure should ideally include assessment of turnout, and the Foot Posture Index can be incorporated to check a change in foot posture from base of gait to turnout. The good intrarater reliability of the Foot Posture Index also indicates that this can be repeated at future appointments by the same practitioner to check progress. Orthoses may be required for nondance footwear, but additional modalities that target the activity are advisable. For example, advice on a reduction in turnout angle to reduce damaging pronatory foot posture changes and taping techniques used to reduce the excessive pronation while increasing proprioceptive feedback and allowing sufficient range of motion for the individual to dance if necessary can be prescribed. It is important to consider that professionals working in a highly competitive environment may not view rest as a feasible treatment option, particularly in smaller companies with fewer dancers to cover for injuries. Treatment plans must, therefore, accommodate these significant factors.

The results indicate that further research is warranted on this subject, but the limitations of this study should be addressed. The measurement tools were quick and easy to use, but more experience in their use before the study would have further improved intrarater reliability. Likewise, the use of dancers familiar with turnout for the pilot study would have enhanced reliability and would have been more representative of the final sample. Time and accessibility made these factors difficult to accommodate in this study, but they are pertinent to future research in this area. The predominant limitation of this study was the small sample size, which was governed by the timeframe of the data collection period and the availability of the dance companies, as minimal inconvenience to dancers and the companies was a priority. The demographic data ranges are illustrative of the vast experience found in contemporary dance companies; however, future studies may benefit from a more focused demographic sample to demonstrate correlation trends.

Despite the small sample, some key relationships were revealed, and a larger-scale study that can group dancers by level of experience would be beneficial. Although previous studies have predominantly involved measurement of hip external rotation and turnout, this is the first study, to our knowledge, to investigate a relationship between turnout and foot posture. The study by Coplan [13] supported the theory that dancers with a functional turnout greater than the available hip external rotation experienced lower-limb injuries. [3,4,11,15,17] The present study indicates that a relationship exists between the pronatory change in foot posture in turnout and injury incidence. Therefore, it would be valuable to include a measurement of hip external rotation in future research to establish whether a relationship exists between foot posture and the difference between available hip external rotation and functional turnout. Assessment of limb dominance should also be included to determine whether this is an influential variable in relation to the significance of the right foot demonstrated in this study. All of the dancers who took part expressed an interest in the study, and it would be pertinent for future research to gain further insight into why the dancers did not visit a podiatric physician for treatment of their foot and ankle injuries in particular, especially because the combined injury rate for this body region was significant. Inclusion of an educational component would be particularly advantageous in future research to promote the profession of podiatric medicine in this patient group.

Conclusions

Turnout is an elementary aspect of dance technique, and previous studies have highlighted its importance and its potential relationship to injury. The aim of this study was to investigate the effect of turnout on foot posture and its association with injury in professional contemporary dancers. The findings of this study indicate that there are grounds to reject the null hypothesis that changes occurring as a result of turnout are not linked to lower-limb injury. Likewise, a relationship between the amount of turnout from base of gait and the number of reported injuries was revealed. A trend toward pronation in turnout was identified along with secondary factors, such as the apparent beneficial effect of skeletal modeling on the number of reported injuries. This study was predominantly limited by the sample size; nonetheless, the results produced were interesting. Although further research in this subject area is warranted, it is evident that a change in foot posture occurs in turnout. These adaptations are a potential etiologic factor in the development of lower-limb musculoskeletal injury in professional dancers.