Knee rotation in classical dancer during the grand plie

For the past two decades, dance researchers and educators have been concern ed about the use of the grand plie and its potential impact on injury incid ence. The purpose of this study was to investigate external longitudinal ro tation (ELR) at the knee during grand plies performed in three classical ba llet leg positions, 2nd, 3rd, and 4th, by professional female ballet dancer s. Light reflective markers were placed on seven lower boyd segments of ten volunteer subjects. Subjects performed three trials of the grand plie and one demi-lie in each of the three leg positions while being videotaped. Mar ker locations were digitalized. Five 'instants' were identified in the plie : begin, demi-lie lowering phase, grand plie, demi-plie rising phase, and f inish. The ELRs at the knee joints for each instant were analyzed using an analysis of variance (ANOVA) and custom matrix analysis. Results indicate t hat ELR values are highest at the bottom of the movement in all positions, and that 3rd and 4th position grand plies present higher overall ELRs than 2nd position. Because ELR at the knee has been named as one of the more ser ious predisposing factors to knee injury, the results of this study indicat e that further investigation about the grand plie is needed, and educators should include grand plies in the training process with caution.