Hip joint health in professional ballet dancers

Submission note: A thesis submitted for the degree of Doctor of Philosophy at School of Allied Health, College of Science, Health and Engineering, La Trobe University, Victoria.

Ballet involves repetitive loading at extreme hip ranges of movement, but there is no conclusive evidence that ballet causes hip joint pathology or osteoarthritis (OA). The overall aim of the thesis was to compare hip joint imaging and clinical findings in male and female professional ballet dancers with age-and sex-matched non-dancing athletes. Study 1-3 compared the prevalence of hip joint pathology (labral tear (Study 1), ligamentum teres tear (LT) (Study 2), and cartilage defects (Study 3), with 3-Tesla magnetic resonance imaging in dancer and athletes, and examined the relationship between hip joint pathology and clinical findings. Dancers had a similar prevalence of labral tear and cartilage defects compared to athletes; however, ligamentum teres appears to be abnormally loaded in ballet, as the prevalence of LT tear was higher in dancers compared to athletes. Studies 1-3 demonstrated a weak correlation between pathology, and clinical measures. Thus, not all imaging findings are clinically relevant. Labral tear, LT tear and cartilage defects were found to co-exist, but prospective studies are required to determine a causal link. Study 4 compared hip bony morphology between dancers and athletes. Dancers had unique bony morphology, such as: greater femoral head-neck junction concavity measured superiorly, higher femoral neck-shaft angles, and lower acetabular version compared to athletes that may contribute to optimal performance in ballet, but high neck-shaft angles and low acetabular version are potential risk factors for hip joint injury. Study 5 investigated the relationship between bony morphology, labral tear, cartilage defects and hip symptoms in dancers. Bony morphology was not related to chondrolabral pathology, but all dancers with cam morphology had cartilage defects. Hip symptoms were not associated with bony morphology or chondrolabral pathology, and a longitudinal study is required to determine if these joint abnormalities are precursors to symptomatic hip joint pathology or OA.