Key Biomechanical Insights For Treating Dance Injuries

Author(s): 
By Thomas M. Novella, DPM

A Guide To Active Plantarflexion (APF) Of The Ankle

All dancers need at least a straight line of foot versus leg. This is required in ballet dancers to pointe, in modern dancers to work on the floor, and in modern and ballet dancers to relevé and tendu. Those who have less than 180 degrees may suffer posterior ankle impingement injuries or midtarsal floor bruises throughout their career.    When it comes to treating APF of the ankle that is inadequate, there are conservative and surgical treatments to address the problem.    A frank lack of plantarflexion in a non-dancer may signal a posterior ankle ossicle. Sliding in baseball or wearing high-heeled shoes can create posterior impingement injuries as can similar hyperplantarflexion trauma.    Technique. Have the patient perform maximal active plantarflexion of the ankle. As you are at eye level with the patient’s ankle, use a straightedge to look for an angular deviation between the distal sagittal third of the leg and the proximal midline of the foot just distal to the talar dome. This should include the dorsal talar/navicular/cuneiform surface but not the metatarsals.    Norms. In female dancers, the norm is 8 degrees or 5 degrees plantarflexed to the tibial line (ballet, modern, respectively). In male dancers, the norm is 3 degrees or 0 degrees plantarflexed versus the tibial line (ballet/modern).

Evaluating Ankle Dorsiflexion With The Knee Flexed

Dorsiflexion of the ankle with the knee flexed (DKF). We actually have DKF when we descend stairs, squat and run up bleacher steps if our calves fatigue. When a dancer has DKF, it is called a demi-plié. The demi-plié is the position from which a dancer (and basketball player) accelerates each leap and absorbs landing shock. Dancers with too little demi-plié may incur symptomatic anterior ankle impingements that are often accompanied by osteophytosis at the anterior ankle margin. Dancers with too much DKF can also suffer anterior impingement injuries as high DKF correlates with a weak or hypotonic soleus, the muscular delimiter of the demi-plié. Low DKF can also cause anterior impingement injury in the non-dancer so it is important to be able to measure it precisely.    DKF technique. The patient lies in a supine position. The examiner holds the sole at 90 degrees to the exam surface while assisting the patient in flexing the knee until reaching ankle end-range of motion. At this moment, the foot will be forced to plantarflex beyond the previously maintained position perpendicular with the exam surface.    Maintaining the patient’s ankle end-range of motion, the examiner assists the patient in slightly extending the hip until the sole again is perpendicular with the exam surface. This is the measurement position. The examiner drops an imaginary plumb line, parallel to the exam surface, from the face of the patella down to the foot. Then he or she notes where the plumb line falls in relation to the foot (first MPJ, talonavicular joint, 2 inches distal to the tip of hallux, etc.).    DKF norms. In male dancers, the norm for DKF is from the first MPJ to 1/2 inch distal to the hallux tip. In female dancers, the norm for DKF is from the first MPJ to 1 inch distal to the hallux tip.

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