Injury and joint hypermobility syndrome in ballet dancers--a 5-year follow-up.

SIR, We have previously reported on the prevalence of joint hypermobility and the joint hypermobility syndrome (JHS) in the Royal Ballet School and Company [1]. In this study, we observed, particularly among the female dancers, that skin hyperextensibility and joint dislocation were the principal clinical features that defined the presence of JHS, having removed joint pain and soft tissue injury from the analysis, given their relatively high prevalence throughout the study cohort. Generalized hypermobility was ubiquitous among the dancers. A key finding, however, was a decrease in prevalence of JHS in ascending from junior school, through the senior school to Company, and within the Company from Corps de Ballet to principal dancer. We suggested that JHS may be associated with a greater risk of injury and/or prolonged periods of recovery post-injury, which may have an adverse affect on career development. In this study, we undertook a 5-year follow-up of previous students in the schools and of the company. Using a self-reporting questionnaire, we identified the frequency and type of injuries and the periods of recovery requiring >6 weeks of rest from dancing. The presence or absence of JHS was defined by the original criteria of skin hyperextensibility and joint dislocation having identified that none of the previously defined non-JHS dancers reported dislocations at present. The response rate was 69% with 93 of the original 135 dancers replying to the questionnaire. Of these, 50 dancers were still within the Royal Ballet Companies; and 55 were females and 38 males. Eighteen (33%) of the females and 12 (32%) of the males had previously been identified as having JHS in the first study [1]. Given that there were no significant differences in the proportion of dancers with JHS compared with what was found in the original study, we concluded that there had been no selection bias for the presence of JHS in the current study. Table 1 shows the data for reporting symptoms for multiple joint pain, cervical, dorsal or lumbar pain, dislocations, ankle sprain, ligament injuries, shoulder capsulitis or fractures. There was no significant difference in reporting between JHS and nonJHS dancers, except for the males, in whom multiple joint pains were significantly more frequent in the JHS dancers than non-JHS. Significant differences were seen in the occurrence of tendon injuries and having had to take time off from dancing for >6 weeks in favour of the non-JHS dancers in females. In men, a similar result was found in both tendon injuries and time off from dancing (Table 2). Dancers suffer from a variety of overuse injuries [2, 3], which have implications for training and performance. The ‘fit to dance’ studies reported that overuse of soft tissue and muscle accounted for 64% [4] and 51% [5] of injuries reported by the UK dance population. The prevalence of soft tissue injuries in our study was similar to these percentages and also similar between males and females. However, we identified that the reporting of at least one or more types of tendon injury was more common in the JHS than the non-JHS dance population for both females and males. Furthermore, dancers with JHS appeared more vulnerable in the sense that JHS was associated with a significantly greater risk of having to take time off from dancing because of injury. The length of time the dancers are off work has not been consistently recorded in other studies. It remains unclear as to whether an injury in dancers with JHS simply takes longer to heal, or whether there is greater tissue damage before the injury is reported, or both. Either way, this study affirms our previous impression that the dancer with JHS is both more vulnerable to the effects of injury and that healing is likely to be more prolonged and may be incomplete. The nature of ballet means that these dancers need to be both strong (powerful) and have stability, stamina and endurance. Muscle and tendon gradually respond to the work load by means of hypertrophy, becoming stronger in response to loading. However, if the loading is excessive, damage will occur either as overuse, premature degeneration or mechanical failure [6]. JHS may be considered a form of collagen deficiency, and in a JHS dance population the tendons may be weaker structurally and slower to respond to training effects, thus leaving them more vulnerable to injury during training or performance. Other causes of stress in a tendon can be due to faulty technique, anatomical factors and muscle imbalance [6]. Dance companies, instructors and health professionals including therapists should recognize the presence of JHS when supporting the injured dancer through a period of recovery, and training should focus on early identification and intervention to prevent injury in these individuals.