If the platform is Macintosh, use the Macintosh style sheet. As a ballet teacher, I am always correcting technical details, especially alignment and position. Too often I notice ballet students struggling to maintain proper alignment while getting in and out of position because of hyperextended legs. For teachers, helping these dancers to be conscious of how to work properly to avoid injury and to gain a strong technique should be a primary concern.
Hyperextension is the extreme extension of a limb or part of the body.
In knees, it is most commonly known as swayback. Most people fall into one or more of these categories. In swayback, the knees are pressed too far backward, leaving the ligaments at the back of the knee permanently stretched. Aesthetically, the line of hyperextended knee gives the leg a graceful curve. Often choreographers will use this exaggeration to enhance their style or for expressive purposes.