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Resource Paper: Turnout for Dancers - Hip Anatomy and Factors Affecting Turnout - Page 2

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Structure of the Hip Joint: The Ball and Socket
The hip joint itself includes two main parts, the ball and socket. The ball of the hip joint consists of the round head of the femur or thigh bone (see Figure 5). The hip socket (described previously and shown in Figure 2), or acetabulum, forms approximately half of a sphere. It is deepened by a horseshoe-shaped piece of cartilage called the labrum. The cartilage is thicker around the socket rim, tapering to a thin layer toward the joint center.



Capsule and Ligaments of the Hip Joint
Enclosing the bones of the hip joint is the hip joint capsule, a sleeve of fibrous connective tissue. The pelvic end of this sleeve is attached around the perimeter of the bony acetabular socket. The thigh end of the capsule attaches at the far end of the neck of the femur. The capsule holds the femoral head in the hip joint and stabilizes it, and does provide some restriction of motion. It is lined by a synovial membrane, which secretes lubricating synovial fluid.

The capsule is reinforced by three major ligaments, which are denser bands of connective tissue. Each of the three ligaments is attached to one of the three bones of the hip socket. The attachments of each of these can be identified by its name: the iliofemoral ligament extends from the ilium on the pelvis to the femur, the pubofemoral ligament connects the pubic bone to the femur, and the ischiofemoral ligament extends from the ischium to the femur. All three of these ligaments become taut in hip extension (as the leg moves backwards in grand battement derrière for example), and therefore contribute to stability while standing. All three of these ligaments become lax as the hip moves into flexion (as the leg moves forwards or in grand battement devant for example).

The iliofemoral ligament (also called the Y ligament) extends diagonally across the front of the hip joint and it is the strongest ligament in the body (see Figure 6). It primarily strengthens the front of the hip capsule, resisting hip extension (raising the leg behind the body to arabesque) and it also inhibits external rotation. This is why it is so difficult to turn out the leg in full arabesque. The pubofemoral ligament strengthens the back portion of the hip capsule, primarily resisting hip abduction (raising the leg sideways to à la seconde). The ischiofemoral ligament resists adduction (moving the leg across the midline) and medial rotation.

The hip is designed more for stability than mobility, the opposite of the situation in the shoulder joint. Consequently, the hip socket is deeper, and the capsule and ligaments are stronger than at the shoulder.

Muscles of the Hip that Create Turnout
The most obvious muscles of the hip are located in the buttocks. The large gluteal muscles act as hip extensors (taking the leg to the back such as in arabesque) and external rotators.

In contrast, the muscles that are more important for turnout, the deep lateral rotators, are small and are buried under the gluteus maximus (see Figure 7). These six lateral rotator muscles are attached to different parts of the pelvis. They all then run laterally, spanning the back of the hip joint capsule and the ischiofemoral ligament. Finally, they all attach on or adjacent to the greater trochanter of the femur. In addition to the six lateral rotators and the gluteus maximus, there are additional muscles around the hip that contribute to external rotation. The sartorius is an external rotator that is thought to be particularly active when the hip is flexed or abducted such as in a passé or front attitude (see Figure 8). The adductor muscles on the inner thigh may contribute to external rotation when the femur is in extension and is already turned out by the primary external rotators. Straightening the legs from the bottom of plié is a good example of using adductors in outward rotation.

Figure 7: Hip outward rotators
Figure 8: Thigh muscles

The function of all six deep rotator muscles is to laterally rotate or turn out the leg, relative to the pelvis. They achieve this goal by pulling the femur's greater trochanter backwards, that is, toward the back of the pelvis. It is often difficult for dancers to isolate the contraction of this muscle group. It is not necessary to tighten or "clench" the gluteals to activate the deep lateral rotators.



This paper may be reproduced in its entirety for educational purposes, provided acknowledgement is given to the "International Association for Dance Medicine and Science."

Copyright © 2011 IADMS, Virginia Wilmerding, Ph.D., and Donna Krasnow, M.S.

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