Figure 3.

Both (a) side splits and (b) front splits are common in flexibility sports and dance. In ballet, these positions are called grand écart facial and grand écart lateral, respectively. These 2 positions as well as the développé à la seconde (c, in ballet; d, in a skater) and the (e) grand plié have been found to cause impingement at the posterior-superior aspect of the acetabulum in morphologically normal hips. Figure (c) reproduced with permission, http://www.shutterstock.com/g/df028. Figure (d) Yuna Kim 2009 World Figure Skating Championships, Los Angeles, California, http://www.flickr.com/photos/queenyuna/6368356397, used under a Creative Commons Attribution-NonCommercial-NoDerivatives License. Figure (e) reproduced with permission, Sergey Petrov, http://www.shutterstock.com/g/irtish.