Iliofemoral ligament
Encyclopedia
The iliofemoral ligament is a ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...

 of the hip joint which extends from the ilium
Ilium (bone)
The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

 to the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

 in front of the joint. It is also referred to as the Y-ligament (see below) or the ligament of Bigelow
Henry Jacob Bigelow
Henry Jacob Bigelow was an American surgeon and Professor of Surgery at Harvard University. He was a vocal opponent of vivisection and was best known for his description of the hip joint and for a technique for treating patients with kidney stones.-Biography:Bigelow was born on March 11, 1818 in...

, and any combinations of these names.

With a tensile strength exceeding 350 kg, the iliofemoral ligament is not only stronger than the two other ligaments of the hip joint, the ischiofemoral
Ischiofemoral ligament
The ischiocapsular ligament consists of a triangular band of strong fibers on the posterior side of the hip joint...

 and the pubofemoral
Pubofemoral ligament
The pubofemoral ligament is a ligament on the inferior side of the hip joint.This ligament is attached, above, to the obturator crest and the superior ramus of the pubis; below, it blends with the capsule and with the deep surface of the vertical band of the iliofemoral ligament....

, but also the strongest ligament in the human body and as such is an important constraint to the hip joint.

Structure

Arising from the anterior inferior iliac spine and the rim of the acetabulum
Acetabulum
The acetabulum is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.-Structure:...

, the iliofemoral ligament spreads obliquely downwards and lateralwards to the intertrochanteric line on the anterior side of the femoral head
Femur head
The femur head is the highest part of the thigh bone . It is supported by the neck of the femur.The head is globular and forms rather more than a hemisphere, is directed upward, medialward, and a little forward, the greater part of its convexity being above and in front.Its surface is smooth,...

. It is divided into two parts or bands which act differently: the transverse part above, is strong and runs parallel to the axis of the femoral neck
Femur neck
The femur neck or neck of the femur is a flattened pyramidal process of bone, connecting the femoral head with the femoral shaft, and forming with the latter a wide angle opening medialward.- Angle of inclination :...

. The descending part below, is weaker and runs parallel to the femoral shaft
Body of femur
The body of the femur , almost cylindrical in form, is a little broader above than in the center, broadest and somewhat flattened from before backward below...

. As the lateral portion is twisted like a screw, the two parts together take the form of an inverted Y.

It is intimately connected with the joint capsule
Joint capsule
An articular capsule is an envelope surrounding a synovial joint.-Layers:Each capsule consists of two layers:* an outer layer composed of avascular white fibrous tissue...

, and serves to strengthen the joint by resisting hyperextension. Its upper band is sometimes named the iliotrochanteric ligament. Between the two bands is a thinner part of the capsule. In some cases there is no division, and the ligament spreads out into a flat triangular band which is attached to the whole length of the intertrochanteric line.

Function

In a standing posture, when the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...

 is tilted posteriorly, the ligament is twisted and tense, which prevents the trunk from falling backwards and the posture is maintained without the need for muscular activity. In this position the ligament also keeps the femoral head
Femur head
The femur head is the highest part of the thigh bone . It is supported by the neck of the femur.The head is globular and forms rather more than a hemisphere, is directed upward, medialward, and a little forward, the greater part of its convexity being above and in front.Its surface is smooth,...

 pressed into the acetabulum.

As the thighs flexes, the tension in the ligament is reduced and the amount of possible rotations in the hip joint is increased, which permits the pelvis to tilt backwards into its sitting angle. Lateral rotation and adduction in the hip joint is controlled by the strong transversal part, while the descending part limits medial rotation.

Turnout
Turnout (ballet)
In ballet, turnout is a rotation of the leg which comes from the hips, causing the knee and foot to turn outward, away from the center of the body. This rotation allows for greater extension of the leg, especially when raising it to the side and rear...

 used in the classical ballet
Ballet
Ballet is a type of performance dance, that originated in the Italian Renaissance courts of the 15th century, and which was further developed in France and Russia as a concert dance form. The early portions preceded the invention of the proscenium stage and were presented in large chambers with...

 style requires a great deal of flexibility in this ligament. As does the front split where the rear leg is hyper-extended at the hip. Many externally rotate the rear leg while doing a front split, this external rotation when the hip is not flexed stretches the ligament even more. This "martial arts split" is distinguished by the rear knee pointing outward sideways (usually the foot along with it) rather than pointing straight down with the patella facing the floor, in a pure extension front split.
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