Measuring Functional Range of Motion in Ballet Dancers' Hips

Original Article

Measuring Functional Range of Motion in Ballet Dancers’ Hips

Suzanne C. Martin, M.A., M.P.T., Felix A. Marquez, M.P.T., Margie A. Ordonio, M.P.T., and Diane D. Allen, M.S., P.T.

Abstract population are significantly different achieve maximal end range. They In this pilot study, values for functional from those of the ballet population and confirmed through the use of radi- range of motion (FROM) at the hip were are not an accurate representation of ography that extreme hip abduction assessed for six female elite ballet danc- a dancer’s requirements.1-4 Inaccurate must occur with progressive external ers ranging from 18 to 30 years of age. assessment of female ballet dancers, in rotation to avoid contact of the greater The feasibility of the MOM© method particular, may result in losses for the trochanter against the ilium. Once of hip FROM goniometric assessment dancer. What appears to be adequate maximal external rotation ROM is was determined so that it might be used ROM using standard normative achieved, slight flexion is required to to create normative tables of FROM for values may ultimately mean either avoid possible impingement of the this population. Results indicate that four injury or loss of a contract for that femoral neck on the posterior wall of out of five end-positions were found to 5 5 be reliably reproducible, and reliability dancer. Although the same issues the acetabulum. across the three investigators was within pertain to the male, this study is One way of measuring ROM while clinically accepted values for four out of focused on the female population. accounting for combined movements five end positions. A preliminary norma- Most ballet hip ROM data has in diagonal planes is to measure while tive hip FROM table was generated that been collected using the standard go- the subject is in a functional upright revealed both high and low FROM values niometric technique, which prescribes position. Although there are no within as well as across dancers. recumbent or sitting positions and studies in the current literature that simple movements in cardinal planes.6 measure ROM of ballet dancers in he athletic and aesthetic Ballet movements, however, are ex- ballet positions, Pink and coworkers8 demands of ballet require full ecuted using combined movements did study lower extremity ROM of external rotation of the hips, in diagonal planes. For example, 14 recreational runners during the T 7 flexibility of the joints, and strength Kushner and colleagues, in a study four phases of gait. They stated that at an extreme range of motion of 22 professional ballet dancers, knowledge of functional ROM mea- (ROM), particularly in the case of reported that hip abduction dance surements would aid the health care the professional female ballet dancer. movements are done with external provider when asking the question, The ROM norms for the average rotation, as well as slight flexion, to “When does it hurt?”8 Measuring ROM in a functional position may Suzanne C. Martin, M.A, M.P.T., is an Intern in the Department of Physical assist the physical therapist in isolat- Therapy at Kaiser Permanente, Hayward, California. ing the occurrence of musculoskeletal symptoms during actual dance move- Felix A. Marquez, M.P.T., is an Intern in the Department of Physical Therapy at ments. Kaiser Permanente, Hayward, California. Although the subjects were not in Margie A. Ordonio, M.P.T., is an Intern in the Department of Physical Therapy functional positions, standardized go- at Sutter Hospital, Redwood City, California. niometric testing does have certain ad- Diane D. Allen, M.S., P.T., is an Adjunct Assistant Professor in the Department vantages. Measurement of joint ROM of Physical Therapy, Samuel Merritt College, Oakland, California. using the universal goniometer has content validity and, in some cases, Correspondence and reprint requests: Suzanne C. Martin, M.A, M.P.T., 1512 criterion-related validity when com- Sherman Street, Alameda, California 94501. pared with radiography.9 Reliability

56 Journal of Dance Medicine & Science Volume 2, Number 2 1998 57

Table 1 Table of Anatomical Landmarks Dancer’s Movement/ Stationary Moving Measurement End Position Fulcrum Arm Arm 1. Hip Flexion with développé en avant/ greater trochanter aligned with lateral condyle slight adduction and quatrième devant en l’air of the femur plumb line of the femur external rotation (ER)

2. Hip Abduction with développé à la seconde/ ASIS aligned with medial condyle slight flexion and ER à la seconde en l’air plumb line of the femur

3. Hip Extension and battement tendu derrière/ greater trochanter aligned with lateral condyle adduction with ER quatrième derrière au terre of the femur plumb line of the femur

4. and 5. Hip Rotation rotation/ internal and mid-calcaneus 0° line drawn on line from external rotation of gesturing foot paper protractor calcaneus to second toe of gesturing foot can also be achieved with the universal Methodology the goniometer during the développé goniometer when examiners are con- Subjects en avant (hip flexion) and développé sistent in lining up the fulcrum and à la seconde (hip abduction) as well both arms with established anatomical Six subjects from the Lawrence Pech as the battement tendu derrière (hip landmarks while subjects are placed in Dance Company, a San Francisco extension). In addition, the protrac- well-defined positions. This consis- professional ballet company, were tor of the goniometer was covered tency and use of a 0° and 180° nota- measured in order to satisfy inter-rater with paper, as suggested in a study tion system has resulted in “normal” and intra-rater reliability data analysis by Horger,11 so that the measuring 10 values as described by authorities such criteria. The six dancers were current examiner could not bias intra-tester as the American Medical Association members of the company, had actively or inter-tester reliability. (AMA) and the American Academy performed in the past three months, A hip rotation guide was devised of Orthopedic Surgeons (AAOS).9 and had no known structural deformi- in order to measure hip rotation in a If specific anatomical landmarks and ties or injuries in the hip. standing position. An 18 by 24 inch well-defined functional positions are Instrumentation piece of newsprint paper was taped to used when measuring a dancer’s hip, the dance floor. It served as a landmark functional hip ROM norms for the The instrumentation used was a for positioning dancers in relation to ballet population may be established, universal long-arm goniometer that the cameras, a standard for orientation with comparable reliability. was adapted to have a rigid z-axis of the dancer’s body to the barre and This pilot study was undertaken perpendicular to the plane formed the room, and as a rotation measure- in preparation for a larger study. The by the stationary and moving arms ment guide. larger study will seek to establish in the x- and y-axes. It also had a Masking tape was attached to the a table of normative values of hip plumb line attached at the fulcrum following bony landmarks to ensure FROM for female ballet dancers in in order to line up the baseline of the the greatest goniometric reliability: common dance positions. The pilot stationary arm with a vertical line. the anterior superior iliac spine (ASIS) study assessed the feasibility of the The rigid z-axis was aligned with the bilaterally, the ipsilateral ischial tuber- instrumentation and the procedures, ASIS of the dominant gesturing leg osity of the measured lower extremity, while also providing an analysis of to accommodate measurement of the medial and lateral condyles of the inter-rater and intra-rater reliability. A hip abduction during the développé femur, the greater trochanter of the preliminary normative table was also à la seconde. The plumb line ensured femur, and the center of the most prepared. verticality of the stationary arm of distal portion of the calcaneus and second toenail of the foot. Only the dominant gesturing lower extremity Table 2 Investigators’ Roles and Order of Rotation for Each Role was taped and measured. Role 1st rotation 2nd rotation 3rd rotation Two video cameras and one still camera were used to provide observa- Examiner 1 / measure Investigator 1 Investigator 3 Investigator 2 Examiner 2 / cameras Investigator 2 Investigator 1 Investigator 3 tion of the examiners’ measuring tech- Examiner 3 / recorder Investigator 3 Investigator 2 Investigator 1 niques as well as to observe postural deviations of each subject during the 58 Journal of Dance Medicine & Science Volume 2, Number 2 1998

Figure 1 End position 1 — quatrième Figure 2 End position 2 — à la seconde Figure 3 End position 3 — quatrième devant en l’air. en l’air. derrière au terre.

Figure 4 End position 4 — external rotation. Figure 5 End position 5 — internal rotation. N = 0° line. measurements of each position. The dancer was then instructed to as shown in Table 2. Procedure assume position on the paper protrac- Examiner 1 lined up the arms of tor positioned on the floor. Figures 1 the goniometer on the subject three The pilot study included six 30-min- through 5 show Positions 1 through times in three distinct trials in each ute measurement sessions. Each 5, respectively. The MOM Method position, then handed the covered dancer was assigned a code number of FROM hip joint measurement, goniometer to Examiner 3 to read. and was given the opportunity to using the parameters listed in Table 1, Examiner 2 operated the video re- warm up as desired. The subjects’ was then performed on the standing corders and still camera. Examiner anatomical bony landmarks were dancer. 3 gave the dancer verbal instructions taped as discussed in the Intrumenta- The examiners rotated among three and recorded Examiner 1’s measure- tion section. roles during the measurement session ment value on the data sheet. Verbal Journal of Dance Medicine & Science Volume 2, Number 2 1998 59

Table 3 Summary of Intra-observer Reliability Data This was called the “neutral” position of the dominant foot. The other End Position/Measurer (significant F > 4.1) F R foot was then placed in the sixth posi- Position 1 Quatrième devant en l’air tion, parallel and next to the dominant Investigator 1 2.973 0.936 foot. The instruction, “turn-out,” was Investigator 2 0.367 0.922 given; and the subject externally and Investigator 3 0.792 0.972 Position 2 À la seconde en l’air bilaterally rotated both hips, after Investigator 1 0.006 0.889 which Examiner 1 marked the mid- Investigator 2 0.204 0.737 calcaneus point and second toe point Investigator 3 5.985 0.707 of the dominant lower extremity on Position 3 Quatrième derrière au terre the paper. These two points were Investigator 1 2.673 0.608 used to create a moving axis line for Investigator 2 0.709 0.559 external rotation as shown in Figure Investigator 3 0.192 0.738 6. The subject then returned back to Position 4 External rotation neutral position before the succeeding Investigator 1 1.508 0.982 two trials and was instructed to look Investigator 2 1.894 0.984 forward as she externally rotated for Investigator 3 3.245 0.964 Position 5 Internal rotation the subsequent trials. Investigator 1 1.557 0.834 Internal rotation end-position was Investigator 2 0.862 0.771 measured similarly. The dancer started Investigator 3 1.321 0.834 in neutral sixth position. She was then instructed to first externally rotate the non-dominant lower extremity and Table 4 Summary of Inter-observer Reliability Data then internally rotate the dominant lower extremity. Again a moving axis End Position (significant F > 4.1) F R line was created for internal rotation Position 1 Quatrième devant en l’air 0.489 0.985 by the two points connecting the mid- Position 2 À la seconde en l’air 5.251 0.93 calcaneus to the second toe, as shown Position 3 Quatrième derrière au terre 1.125 0.743 in Figure 6. Position 4 External rotation 0.138 0.983 Position 5 Internal rotation 2.584 0.909 All five measurements were taken three times by each of the three investigators, which resulted in each dancer achieving each dance position nine Table 5 Summary of Mean Range of Motion Measurements times. Position 1 Position 2 Position 3 Position 4 Position 5 Quatrième À la seconde Quatrième External Internal Results Subject devant en l’air en l’air derrière au terre Rotation Rotation Three investigators each recorded data 1 106° 108° 28° 82° 31° for 3 trials of 5 end positions in 6 2 138° 130° 22° 83° 16° dancers. The data was analyzed using 3 100° 125° 28° 71° 23° a repeated measures analysis of vari- 4 114° 124° 31° 93° 29° ance (ANOVA) to obtain the values 5 127° 123° 30° 81° 28° necessary to calculate the intraclass 6 113° 122° 30° 62° 37° correlation coefficient (ICC).10,12 The ICC version (2,1)12 was used to calculate intra-rater reliability because instructions consisted of, “ready, was instructed to allow Examiner 1 to of the use of single measurements in and,” upon which the subject would “place the foot” correctly aligned with the formula rather than the use of assume a passé position from fifth the inked spot where the fulcrum of the means of the measurements. This position, and then développé front the paper protractor had been drawn. produces more useful clinical infor- and side respectively for Positions 1 The posterior mid-calcaneus of the mation since most physical therapists and 2. The subject assumed the posi- dancer’s dominant foot was placed at take only one ROM measurement of tion of quatrième derrière a terre for the inked spot. The dominant foot a particular joint at any one time. The 12 Measurement 3. Measurements 4 and was outlined and the second toe posi- ICC version (2,k) was used to cal- 5 consisted of two end positions, one tion was marked on the paper. Figure culate inter-rater reliability. For inter- in external rotation and the other in 6 shows the neutral axis created using rater reliability, the mean of several internal rotation. External rotation a line intersecting the inked spot and measurements was used because the was measured as follows. The dancer the second toe mark. mean is considered to provide a better 60 Journal of Dance Medicine & Science Volume 2, Number 2 1998

N indicating significant variability of to 130°. End Position 3, “quatrième IR ER these measurements. End Positions 1 derrière au terre,” ranged from 22° to and 4 had R values greater than 0.90, 31°. End Position 4, external rotation, indicating strong reliability of these ranged from 62° to 93° and End Posi- measurements within investigators. tion 5, internal rotation, ranged from Figures 7 and 8 depict contrasting 16° to 37°. intra-rater scores, demonstrating dif- Discussion ferences in reliability of measuring 2 different end positions. Figure 7 illus- This was a preliminary study to test trates the consistency of measurement the feasibility of the instrumenta- values for Position 4, external rotation and the procedures necessary to tion, where the ICC value was greatest determine a normative table of func- at R = 0.984. Most ICC values for tional range of motion (FROM) that intra-rater reliability were greater then physical therapists can use in exami- Figure 6 Hip rotation guide showing 0.75, except for Position 3, “quatrième nation and treatment of professional the inked spot and neutral axis and, derrière au terre,” where R < 0.75 for female ballet dancers. Intra-rater and external and internal moving axis. N = all three investigators. Figure 8 shows inter-rater reliability were analyzed 0 degree line. the variability in measurement values to explore whether the methods and for Position 3, where the ICC value positions could be replicated reliably estimate of the true score, theoretically was lowest at R = 0.559. in a clinical setting. Portney and Wat- kins10 suggest that any R scores of 0.75 reducing error variance. An F-test was Table 4 is the summary of inter- then used to determine if the trials and rater reliability data. As shown, the or higher are to be rated as “good.” the trial means differed significantly. F value for “à la seconde en l’air” is They also claim that clinical settings At p = 0.05, F = 4.1, all F values significant (F > 4.1). The ICCs for prefer a higher standard of reliability, greater than 4.1 indicate significant all positions except “quatrième der- at R equals 0.90 or higher. Using the differences. R is the resultant statistic rière au terre” (at 0.743) are 0.909 or recommendations of Portney and after performing an ICC calculation. higher. Watkins’ reliability standards, intra- R values above 0.75 indicate good reli- Table 5 shows the summary of rater and inter-rater reliability were assigned to the data and are presented ability. R values above 0.90 represent mean ROM measurements for the 10 strong reliability. five end positions of all six subjects. in the Results section. A summary of intra-rater reliability Measurements for End Position 1, The findings of this pilot study data is shown in Table 3. Only one “quatrième devant en l’air,” ranged indicate that further improvements F value was above 4.1: “à la seconde from 100° to 138°. End Position 2, “à in the measurement methods and en l’air” by the third investigator, la seconde en l’air,” ranged from 108° procedures, especially for measurement 3 (the quatrième derrière au

End Position 4 / External Rotation 100

60 End Position 3 / Quatrieme derriere 35 50 30

40 25 Measurer 2/Trial 1 30 20 Measurer 2/Trial 2 Measurer 2/Trial 3 15 Degrees of End Range End of Degrees 20 10 10 trial 1 trial 2 trial 3 5

0 Degrees of End Range 0 1 2 3 4 5 6 1 2 3 4 5 6 Subjects Subjects Figure 7 Intra-rater reliability graph. End Position 4, external Figure 8 Intra-rater reliability graph. End Position 3, rotation, where R = 0.984. quatrième derrière au terre, where R = 0.559. Journal of Dance Medicine & Science Volume 2, Number 2 1998 61 terre end-position), could be made in are more relevant to dancers when hypermobility in Positions 1 and 2, or a future study incorporating a larger measured as multi-planar motions. hypomobility in Position 5). It would sample. This finding was surprising Measurement 1, for example, ranged also provide an objective method on considering the ease of measuring this from 100° to 138° in the six dancers, which to base preventative measures position for both the examiners and which spans the AAOS measurement for individual dancers. the subjects. Pelvic tilt was considered for hip flexion (120°). However, the FROM measures, whether used as by taking an additional measurement, AAOS measurements are taken with a a screening tool or injury evaluation and photographing this measurement. flexed knee, and no hip rotation, and tool, could be beneficial to the dancer, Anterior tilt was not considered a sig- so provide little beneficial information physical therapist, teacher, and chore- nificant problem since it only ranged to a ballet dancer who is required to ographer. The physical therapist can from 5° to 10° among the subjects. hold the position quatrième devant en use this information, in conjunction However, later photographic observa- l’aire. A validation study to compare with strength measures and motor tions indicated that pelvic rotation in the FROM measurement methods skills measures, in order to determine the coronal plane varied considerably described here with radiographic where individual dancers compensate among the subjects. This was interest- measurements would be a logical next to produce FROM and thus need ing given that the subjects performed step. Better comparisons can then be preventative intervention with laxities at an elite level. Perhaps another made between FROM values and and/or lack of mobility, strength, and physical tool could be employed for standardized uniplanar norms. motor control. The dancer can then measurement 3 to help neutralize the This study’s strength, therefore, use this information to work toward frontal plane alignment of the bilateral is that this method for comparing managing and correcting these areas. ASIS anatomical landmarks through- FROM might aid in fine-tuning the The teacher can train the individual out the measurement. The findings process of defining and classifying dancer within the limitation of his or also support that in four out of five injury. Pink and colleagues’ functional her body. The choreographer can be dance positions, the reliable use of the range of motion study for runners made aware of the special needs of goniometer, even if it is adapted, can helped athletes answer the question, each dancer. be accomplished in functional, non- “When does it hurt?”8 Perhaps a simi- To summarize, these female ballet standard test positions, across several lar question for dancers is, “Where dancers undoubtedly have different examiners, given compliance with the is the extra range of motion coming hip ROM when compared to the goniometric requirements of using from?” FROM measurements used in average population. Goniometric standard bony anatomical landmarks. combination with functional strength measurement in functional positions Limitations of the study include and active ROM measurements can is essential when fully assessing the its focus on a small number (n = 6) assist a physical therapist in deter- dancer’s injury and in determining of elite female ballet dancers as well as mining which muscles or joints may the compensatory patterns of the indi- the functional positions representing be overstressed in compensation for vidual dancer. Therefore, establishing the combined ROM values of multi- thightness or weakness elsewhere. norms for the female ballet population planar dance movements. However, Further development and subse- in functional positions may prove the findings demonstrate a discrep- quent clinical use of functional dance beneficial to the physical therapist ancy between the FROM of these position measurements can be benefi- working with this population. dancers and the norms established cial in at least two comparative ways. Conclusion for cardinal plane hip ROM in the First, the values could be compared average population. For example, the to future normative FROM tables es- The purpose of this study was to docu- American Academy of Orthopaedic tablished for this population in order ment hip ROM in professional female Surgeons (AAOS) records 45° for to compare abilities between dancers. ballet dancers as measured in dance both hip external and internal rota- Second, and perhaps the most infor- positions. This pilot study assessed the tion in the cardinal plane.9 These mative use, could be the comparison feasibility of the instrumentation and values differ from Postions 4 and 5, of FROM measures within one danc- the procedures necessary to imple- which were also measured in single er. For instance, in looking at Subject ment a full normative study. Four planes, as indicated in Table 5. Ex- 2 in Table 5, it can be seen that she out of five end-positions were found ternal rotation is consistently higher displays greater ranges of hip motion to be reliably reproducible to a good and internal rotation is consistently in Postions 1 and 2, and the least in degree, indicating that the methods lower than the AAOS measurements. Position 5, when compared to the of measurement can be generalized Although the movement was mea- other four subjects. This method of to a clinical setting. Reliability across sured at the feet in this study, which comparision of an individual against examiners also rated within clinically would include any rotation possible a future FROM table of elite female accepted values for four out of five for hip, knee, and ankle, the rota- ballet dancers might aid in identifying end-positions. Further development tion should always be greater when injury incurred through compensa- of methods and procedures is espe- summed. The first three positions tory mechanisms (for example, joint cially warranted for the quatrième 62 Journal of Dance Medicine & Science Volume 2, Number 2 1998 derrière au terre and à la seconde en LA, Kushner SF: Lower extremity 18:286-291, 1990. l’air end positions. However, using flexibility patterns in classical bal- 8. Pink M, Perry J, Houglum PA, this technique, a preliminary norma- let dancers and their correlation to Devine DJ: Lower extremity range tive hip FROM table was generated, lateral hip and knee injuries. Am J of motion in the recreational sport demonstrating that professional fe- Sports Med 15:347-352, 1987. runner. Am J Sports Med 22:541- 3. Micheli LJ, Gillespie WJ, Walaszek 549, 1994. male ballet dancers, especially those at A: Physiologic profiles of female 9. Norkin CC, White DJ: Measurement an elite level, are a special population professional ballerinas. Clinics Sports of the Joint: A Guide to Goniometry. whose ROM values fall beyond the Med 3:199-209, 1984. Philadelphia: F. A. Davis Co., 1995. passive ROM values of the average, 4. Sammarco GJ: The dancer’s hip. 10. Portney L, Watkins M: Foundations non-dancing population. Of special Clinics Sports Med 2:485-498, of Clinical Research: Applications to note: measuring ROM in dance posi- 1983. Practice. Norwalk, CT: Appleton & tions can help reveal specific compen- 5. Garrick JG, Requa RK: Ballet inju- Lange, 1993. satory movements used by individual ries. Am J Sports Med 21:586-590, 11. Horger M: The reliability of gonio- dancers. 1993. metric measurements of active and 6. Pearsall AW: Assessing acute hip passive wrist motions. Am J Occup References injury. Phys Sports Med 23:36-48, Ther 44:342-348, 1990. 1. Hamilton WG, Hamilton LH, 1995. 12. Baumgartner TA, Jackson AS: Marshall P, Molnar M: A profile of 7. Kushner S, Saboe L, Reid D, Penrose Measurement for Evaluation in Physi- the musculoskeletal characteristics of T, Grace M: Relationship of turnout cal Education and Exercise Science. elite professional ballet dancers. Am to hip abduction in professional Dubuque, IA: William C. Brown J Sports Med 20:267-272, 1992. ballet dancers. Am J Sports Med Publishers, 1987. 2. Reid DC, Burnham RS, Saboe