Key Biomechanical Insights For Treating Dance Injuries

After completing my residency and an orthopedics fellowship at the New York College of Podiatric Medicine, I quickly became a medical advisor to world-class athletes. In the dawn of the sports medicine era back in 1980, I joined a multidisciplinary dance-health facility and saw up to 30 dancers a day. New York City was the dance capital of the world and some surveys reported that 80 percent of dancers sustain career-threatening foot/ankle injuries.    Unfortunately, my biomechanics training applied more to the average Joe but not the dancer. I found that the concepts from Root and others who were founding fathers of podiatric biomechanics did not apply to dancers, who spent little time engaging their subtalar joints in ground reaction. Dance involved a fixed set of extreme positions, an archetypal soup for overuse injury. It did not seem like there was an exact way to measure ankle ranges of motion. I was rattled by these challenges. Then a soft-spoken dancer from A Chorus Line walked into my office and my life changed.    “Doc, I have Achilles tendonitis because I cannot point my foot all the way, see?” Although he actually had a posterior impingement injury in his ankle, what sobered me was his expectation that I would see a pathological lack of ankle plantarflexion. I did not have a clue what he was indicating. Realizing this might be an epiphany, I exposed my unjustified reputation and said, “Danny, what are you looking at?” Through poorly veiled surprise, he pointed to the dorsal surface of his foot distal to the talar neck and compared it to the distal sagittal third of his tibia.    A light went on for me. I was looking at what a dancer looks at when critiquing ankle plantarflexion. It was easier to see and precisely measure than published orthopedic methods that compared the fibula to the fifth metatarsal but were oblivious to the influences of the interposed joints. All I needed was a pencil, a little hardware store circular level or eventually just my eyes, and I could precisely measure talar plantarflexion.    Concentrating on foot and ankle function during dance, I carefully observed classes and performances. In a few months, I was able to use simple, accurate, replicable techniques to measure ankle ranges. Then I related these requisite ranges of motion to the common set of hallmark dance injuries. I was able to establish a database, based upon the 1,500 professional dancers I had already seen by the late 1980s, in which excesses or inadequacies in ranges correlated strongly with particular injuries. I have used and lectured about this framework in my dance injury practice, sports medicine practice and general podiatric practice throughout my career.    That said, let us take a closer look at some evaluation techniques and clinical implications with dance-related injuries.

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.

Key Pointers For Assessing The DKE Position

Dorsiflexion of the ankle with the knee extended (DKE). This is a measurement of gastroc tension or “calf flexibility.” When calves are too tight, the patient may have resulting tensile injuries such as forced subtalar and midtarsal pronation, and Achilles tendinitis. Patients with calves that are too loose are susceptible to injuries from inadequate eccentric (decelerative) or concentric (accelerative) gastroc function. In addition, excessive DKE over-recruits the flexor hallucis longus (FHL) as an accessory ankle plantarflexor. The FHL is also responsible for medial stabilization of the ankle en pointe, and toggling between pointe and demi-pointe. FHL tendinitis is called the “dancer’s tendinitis” due to this FHL multitasking in dancers.    Too much DKE also correlates with heel and leg impact problems like heel bruises and tibial or fibular stress fractures. A hyperflexible calf is like a bungee cord that is too long. The DKE technique uses no goniometer and allows clinicians to measure with more of a linear value rather than radial value. I define DKE as the minimal slope of the shoe necessary to enable subtalar neutral. Due to the overpowering mechanical advantage of the gastroc, if a patient has a negative 3/4-inch DKE, the foot will pronate in any shoe with a heel height less than 3/4 inch. Conversely, the gastroc will not reach full length/tension in shoes higher than a 3/4-inch slope. This sets the stage for eccentric injuries.    Technique. The patient is in a supine position with legs fully extended. The examiner crouches to eye level with the sagittal ankle. The examiner grasps the fifth metatarsal head and maximally extends the knee while locking the midtarsal (by exerting a dorsiflexion/eversion moment at the fifth metatarsal head). The examiner maintains a subtalar neutral position with gentle palpation by the opposite hand. (Note that forceful palpation elicits apprehensive active dorsiflexion and invalidates the exam.) With the patient at the end range of passive dorsiflexion, the examiner drops an imaginary plumb line, perpendicular to the leg’s long axis, from the plantar fifth metatarsal head down to the heel. The distance between the inferior heel nadir and plumb line is the DKE value.    When the patient has end range of motion with the fifth metatarsal head stopping plantar to the heel, there is a negative DKE value (gastroc equinus). If the fifth metatarsal head stops dorsal to the heel, there is a positive DKE value. The DKE value represents the heel height required to maintain subtalar neutral. I have found that examining for the DKE value is the single most important examination in my practice.

Understanding Hallux Dorsiflexion With The Ankle Fully Plantarflexed (HDP)

Dancers spend a lot of time landing, posturing, leaping and turning from the tiptoe position (demi-pointe). The dancer’s hallux must dorsiflex 90 degrees to accommodate her or his plantarflexed ankle, an amount significantly higher than the non-dancer norm of 60 to 65 degrees. If a dancer’s hallux cannot dorsiflex this much, he or she may be susceptible to plantar plate injury, medial first MPJ collateral sprains, dorsal impingement at the first MPJ or compensatory weight shifts to the hallux/functional hallux limitus or toward lateral ankle instability. Inadequate HDP is a major cause of morbidity in the dance population.    Technique. The patient maximally plantarflexes the ankle. The examiner assists the patient in holding this position. The patient then dorsiflexes the hallux to end range of motion. One would compare the line made by the plantar aspect of the first MPJ and the hallux plantar surface to the distal anterior margin of the leg while the ankle is maximally plantarflexed. The hallux-MPJ line must be 90 degrees or more acute to the previously described APF leg line.

In Conclusion

For over 25 years, my general practice has enjoyed consistently favorable outcomes in the treatment of dance injuries. I hope the biomechanical concepts that I have learned in treating this specific patient population over the years can be beneficial in your practice as well.    Dr. Novella is an Adjunct Clinical Professor of Podiatric Orthopaedics at the New York College of Podiatric Medicine. Dr. Caselli is a staff podiatrist at the VA Hudson Valley Health Care System in Montrose, N.Y. He is also an Adjunct Professor at the New York College of Podiatric Medicine and a Fellow of the American College of Sports Medicine.