NEW YORK, NY—"High School Musical 2" strutted into history as the most watched basic cable telecast of all time (and the most watched TV telecast ever for young people ages 6 to 11), and an increasing number of those viewers are among the thousands now swelling enrollments at dance schools nationwide. Dance medicine researchers suggest that many will eventually end up in the offices and clinics of orthopaedic surgeons or rheumatologists with some type of dance-related musculoskeletal problem. Donald J. Rose, MD, who heads the world-famous Harkness Center for Dance Injuries at New York's Hospital for Joint Diseases, warns that clinicians need to learn some new steps of their own to care for these patients.
Iliopsoas problems almost unique to dancers
The iliopsoas muscle lies in front of the hip joint and is the main hip flexor [Figure 1].
Dancers with iliopsoas problems may complain of pain in the hip and thigh region, hip stiffness, and a clicking or snapping feeling in the hip. Iliopsoas tendonitis results from repetitive hip flexion or overuse. Iliopsoas syndrome results from a rupture or tear in the muscle following a sudden contraction and occurs most often at the point where the muscle and tendon connect.
Dr. Rose warned that clinicians should carefully rule out iliopsoas syndrome before rushing to MRI in a search for tears of the labrum in dancers who present with hip pain. "The most useful physical examination to test for tightness and iliopsoas syndrome is resisted hip flexion with the patient's legs in the externally turned out position," he explained. "You should not be able to push down the knees of a dancer in this position. If you can, something is wrong with the iliopsoas."
"Hip arthroscopy is vastly overused in treating dancers who present with hip complaints," Dr. Rose said. "This seems to be due to lack of knowledge of how to diagnose and treat iliopsoas syndrome. MRI is not useful for this problem because it is very inaccurate."
Another unusual problem is the os trigonum posterior ankle impingement syndrome. The os trigonum is an accessory bone shaped like a smooth pebble and is found just behind the ankle joint present in 5% to 15% of otherwise normal feet. When ossification of this bone does not fuse with the rest of the talus during development, this bone can become pinched in the space behind the ankle when a ballet dancer assumes the pointe or demi-pointe positions, which maximally plantarflex the ankle. "This problem occurs almost exclusively in classically trained ballet dancers," said Dr. Rose, who describes the result as "trigger finger of the big toe."
Knees are the third major area of concern in dance medicine. Dr. Rose recommends a quick screening test. "Have the dancer assume a second position plié [Figure 2], then examine the knee, hip, and back alignment. 
Dancers who have anatomy-based problems may try to force better ‘turnout' by twisting the knees. Also, many people have asymmetry of the hips, and a dancer may force turnout on the bad side to meet that of the good side. This is often accomplished with hyperlordosis of the lower back. Among other problems, this can predispose to stress fractures of the lower back," he stated.
Study the dancer as well as the dance
Above all, Dr. Rose emphasized that dancers are not like other patients, even other athletes.
"Physicians must be constantly aware of how important dance may be to the patient's overall life. Don't tell an injured dancer to just stop dancing for 6 weeks to rest an overused joint. Either the patient will never come back to you, or he or she will consult another practitioner or seek some form or alternative care. Keep them dancing. Work around their issues. Clinicians should understand the concept of ‘marking.' Identify the specific movement that is contributing to the problem, and help the dancer devise ways to work around it until the injury heals."
Finally, especially for surgeons, Dr. Rose stressed the importance to the dancer of maintaining range of motion. "I handle many aspects of care differently for dancers than for other patients," he said. "For example, anterior cruciate ligament (ACL) repair. In a football player with a torn ACL, stability is the primary concern, and operative technique that produces the most stable repair is the best one. If a football player loses 5° of range of motion as a result, that doesn't much matter. For a dancer, losing 5° of range of motion could well mean the end of a career."
Dr. Rose advises clinicians treating dancers of any age, including children, to learn more about dance and about dance medicine. "Take a course!" he suggested. "Consult the International Association for Dance Medicine & Science Web site (www.iadms.org) and read their journal. Learn about the basic positions, especially in classical ballet, and what it takes to be a dancer."
Dance medicine programs are springing up or expanding to meet this challenge. CIAOMed identified 27 programs at US medical centers that focus on dancers and other performing artists.
Dr. Rose also noted the challenge of providing care to many dancers who have inadequate or nonexistent health insurance. "This was one of the reasons we founded the Harkness Center for Dance Injuries," he said. We wanted the ability to provide quality skeletal care to dancers regardless of their ability to pay. We raised special funds to permit this, and we have a sliding scale. Which is a good thing, since the year we opened the center (1987) we found that our dancer patients had an average annual income of $7000."
Anatomy, technique both contribute to injury risk
Factors thought to contribute to increased risk of injury for dancers include muscle imbalances of the hip, muscle imbalances of the gastrocsoleus equinus, plantarflexion, hallux rigidus, foot type, lumbosacral pelvic alignment, and knee alignment.
Most ankle injuries in ballet dancers occur during pointe or demi-pointe work, reflecting the 180° of plantar flexion relative to the central axis of the tibia and foot required to perform full pointe. An MRI study of ballet dancers' foot and ankle injuries presented at the Radiological Society of North America 2002 meeting and reported in Diagnostic Imaging Online showed posterior impingement in 12 of 20 scans, four of which also showed signs of os trigonum.1 Lead author of that study Julia C. Hillier, MD, commented, "Impingement syndromes of the ankle are painful disorders that limit the full range of movement. Although unusual in the population as a whole, they are relatively common in young athletes, and in particular in ballet dancers."
The dancers' scans also showed a high incidence of flexor hallucis longus tendonitis and of bone marrow edema within tarsal bones. "A range of foot and ankle injuries are sustained by ballet dancers. Although posterior impingement and os trigonum complex are well recognized in this group, there needs to be a high index of suspicion for other injuries, in particular flexor hallucis longus tendonitis and stress responses," the researchers concluded.1
With regard to back injuries, Treg Brown, MD, and Lyle J. Micheli, MD, with the division of sports medicine at Children's Hospital, in Boston, wrote in BioMechanics, "The center of body mass lies just anterior to the second sacral segment. The body will strive to maintain this center of mass throughout most movements, dance, or otherwise. Achieving and maintaining such alignment requires various concentric and eccentric contractions of the muscle groups mentioned. When this delicate balance is disrupted, either intentionally (as to improve hip range of motion through altered technique) or unintentionally, an imbalance results. The imbalance will result in a deficiency that may manifest as a hyperlordotic lumbar spine. Hyperlordosis appears to be a factor in a majority of dance-related cases of low back pain."2
Drs. Brown and Micheli also note that among ballet dancers, the attempt to achieve the ideal turnout position of 180° external rotation of the lower extremities may lay the groundwork for later hip problems. "Ballet dancers are well known for the immense effort they will devote to achieving ideal turnout. These efforts routinely begin at a young age, thanks to the common belief that the femoral neck may be molded into greater retroversion through a series of exercises and stretching techniques." After about age 11, emphasis may shift to stretching the hip capsule and the iliofemoral ligament. This can set the stage for "calcium deposition, osteophyte formation at the femoral neck, and increased compression at the superolateral border of the acetabulum, ultimately resulting in early arthrosis of the hip." Hamilton et al recently reported that girls who underwent dance training for 6 hours a week or more from ages 11 to 14 had significantly less femoral torsion than girls who had less than 6 hours of dance per week, but this had no influence on their execution of turnout.3
Young dancers are also likely to try to compensate for poor anatomy with poor technique, such as forcing turnout from below the knee. This redirects force medial to the foot rather than down onto the second metatarsal, generating abnormal tensile forces across the medial aspect of the knee and the first metatarsophalangeal joint, according to Drs. Brown and Micheli.2
These factors translate into increased risk of arthritis. Van Dijk et al found that, compared with nondancers, former professional female ballet dancers had increased arthrosis of the ankle, subtalar and first metatarsophalangeal joints, which they attribute to repetitive microtrauma.4
Dancing builds bones, helps older adults keep moving
Dance researchers also report some significant benefits. One is increased bone health in girls who dance throughout the years of puberty. Matthews et al measured bone mineral density over 3 consecutive years in 82 ballet dancers and 61 controls ages 8 to14. They report that the dancers had significantly greater bone mineral content in the total body, lower limbs, femoral neck, and lumbar spine.5
Researchers are also documenting benefits of social dancing for older adults. Verghese reports that, compared with nondancers, those who danced regularly had better balance, a longer mean stride, and a more stable gait pattern during walking. They also had reduced stance time, longer swing time, and shorter double support time.6
References
1. Gould P. Ballet dancers' MR scans keep doctors on their toes. Diagn Imaging Online. August 21, 2003. Available at: http://www.diagnosticimaging.com/dinews/2003082101.shtml.
2. Brown T, Micheli LJ. Where artistry meets injury. BioMechanics. September 1998. Available at: www.biomech.com/db_area/archives/1998/9809dance.12-24.bio-.html.
3. Hamilton D, Aronsen P, Løken JH, et al. Dance training intensity at 11-14 years is associated with femoral torsion in classical ballet dancers. Br J Sports Med. 2006;40:299-303.
4. van Dijk CN, Lim LS, Poortman A, et al. Degenerative joint disease in female ballet dancers. Am J Sports Med. 1995;23:295-300.
5. Matthews BL, Bennell KL, McKay HA, et al. Dancing for bone health: a 3-year longitudinal study of bone mineral accrual across puberty in female non-elite dancers and controls. Osteoporos Int. 2006;17:1043-1054.
6. Verghese J. Cognitive and mobility profile of older social dancers. J Am Geriatr Soc. 2006;54:1241-1244.
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