The demi-plié is performed countless times in any dance class, rehearsal, or performance. Because it is such a common movement, it would benefit the dancer to have good technique to decrease his or her risk for injury.
Patella Over Second Toe
In a demi-plié, your patella – or knee cap – should be centered over your second toe. Often times when I watch dancers perform demi-plié, I see the patella drift over the big toe or even further forward–or medial to the toe. This may be indicative of forced turnout or decreased use of your deep hip external rotators. Performing demi-pliés this way increases stress on the knee joint and surrounding structures.
Another indicator that a dancer may be forcing their turnout is the presence of over-pronation of the feet. Pronation is when the medial longitudinal arch of the foot – commonly known as the instep – collapses towards the ground. Over-pronation increases stress on the foot, ankle, knee and even at the hip and can predispose a dancer to tendinopathies.
Pelvis in Neutral
When assessing a dancer's plié, it is also important to look up the chain at the pelvis. The placement of the pelvis influences the position of the spine. If the pelvis is not in a neutral position, the spine may no longer be in a position where it can most effectively attenuate forces coming from the floor or from the upper body. This puts stress on the spine and surrounding areas. Additionally, the position of the pelvis sets up how efficiently a dancer can use his or her lower extremity and trunk muscles.
Heels on Ground
Yes, technically a demi-plié is, by definition, a position in which dancers are meant to keep their heels on the ground. That said, it is still important to remember this part of your plié technique especially when the it is used as a transitional step or as a landing from a jump. Performing a demi-plié with your heels off the ground increases stress on your Achilles' tendon and other soft tissue structures that cross the ankle.
A word of caution: These are not the only things to look for. If you think your plié is not technically sound or if you have additional questions about this step's execution, look to a dance medicine specialist to help you figure out what might need to be addressed. Happy dancing!