Wednesday, February 16, 2011

The Dancer’s Hip

By William G. Hamilton, MD

How’s your turnout? Wish you had more? Most dancers do, so let’s take a look at the dancer’s hip.

First the anatomy

As you probably know, the hip is a ball and socket joint. The ball is the uppermost part of the thighbone, or femur, and the socket is the acetabulum (Latin for vinegar dish). This arrangement allows motion in all planes:

Rotation: Internal, or toeing in, vs. external, or toeing out. Adduction: toward the midline, e.g., when crossing your legs in fifth position. Abduction: away from the midline, e.g., second position. Forward motion: flexion, as in tendu or battement to the front. When you sit, the hip is flexed. Backward motion is extension.

Can you improve your turnout?

Not much. The extent of this motion is limited by the alignment and architecture of the ball and socket joint itself. Still, the range of motion varies considerably from one person to another and from one hip to the other in the same individual.

The normal hip has roughly an equal amount of internal and external rotation. If you are born “pigeon-toed” you will have more turn-in than turnout. The opposite type of hip, “duck-footed,” is naturally turned out and perfect for ballet. How much your natural turnout can be improved by early training is controversial. The orthopedic literature suggests that turnout, or anteversion in medical parlance, is mostly determined by age 12. It can be slightly improved by early training and stretching, but not dramatically. The rotation you have at age 12–13 is pretty much what you are stuck with.

Turning out below the hip

The second component of turnout is the knee, or actually the tibia, or shinbone below the knee, which is normally rotated outward 10–15 degrees. This rotation has a fancy name. It is called external tibial torsion, and this also varies. Some dancers with good turnout in the hip can lose some of it below the knee, while others with mediocre rotation in the hip can gain it below.

The third component is the foot and ankle. But, as all well-trained dancers know, you should not get your turnout by twisting either your knee or your foot out and rolling in—the cardinal sin of ballet.

It is OK to “nudge” your hip to get all of the turnout that is present, but forcing it too hard can injure it. There is a cartilaginous rim that runs around the edge of the socket called the labrum (lip). When the rotation is pushed too far this lip can actually be torn loose from its attachment. The torn labrum can cause a lot of trouble and sometimes requires arthroscopic surgery to fix it. (More on this later.)

Special circumstances

Hypermobile dancers, whose joints are too loose, are especially prone to labral tears and damage to the joint. By forcing their turnout, they can actually slip the hip partly out of joint. That’s called subluxation. Hypermobility comes in various degrees from mild to severe— as in the Indian Rubber Man in the circus who can tie himself into knots, or contortionists. There is no cure for this, but hypermobile dancers need to become extra strong with physical therapy exercises to control their looseness. They also need to be very careful with their technique.

Acetabular dysplasia. Some dancers are born with a hip socket that is too shallow. They usually have a very good range of motion— sometimes too good. This type of hip is very prone to labral tears and early arthritis and should not be turned out at all. This condition can be picked up on a MRI study. Acetabular dysplasia is not common, but when it is present it is a relative contraindication to ballet or turning out because this can easily rotate the hip partly out of a socket that is already too shallow. These dancers should dance parallel to protect their hips.

Labral tears are characterized by sudden pains in the groin that often occur with certain motions like moving sideways, or developé à la second. There is a specific test for labial tears during the physical exam: With the patient lying down on her back (supine), the affected hip is flexed first straight up toward the chest with the knee bent. This is usually not painful. But when the knee is brought up in the same motion but more toward the midline (adducted) it will cause pain in the hip if a labral tear is present. That’s “the flexion-adduction sign.” It is not 100 percent accurate, but is highly suggestive and is usually an indication for getting a special MRI. Some labial tears are not very painful, so a physician will just keep an eye on it over time. If it gets worse, the dancer may need arthroscopic surgery to fix the problem.

Dancers who turn out may be prone to arthritis of the hip later in life, but this is not known for sure because the condition often occurs even in non-dancers. Symptomatic arthritis is the usual indication for a hip replacement.

Remember that with turnout, like many things in dance, it is important to know your limitations and to work within them. “Forcing the envelope” can lead to injuries. Merde!

William G. Hamilton, MD is an orthopedic surgeon in private practice in New York City. He is the orthopedic consultant for the New York City Ballet, American Ballet Theatre, the School of American Ballet, and the JKO School of Ballet at ABT. He specializes in foot and ankle injuries in dancers and athletes. He is past president of the American Orthopedic Foot and Ankle Society.

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