Ischiofemoral ligament

At a glance

English

Ischiofemoral ligament

Latin (TA2)

Ligamentum ischiofemorale

System

Ligament

Region

Lower limb

Side

Paired, left and right

About the ischiofemoral ligament

Three ligaments thicken the fibrous capsule of the hip: the iliofemoral in front, the pubofemoral below and the ischiofemoral behind. The ischiofemoral ligament is the posterior one. It is a triangular band of strong fibres that begins on the body of the ischium, behind and below the rim of the acetabulum.

From there its fibres spiral upwards and laterally across the back of the femoral neck. Some turn inwards to merge with the zona orbicularis, the ring of circular fibres that hugs the neck, while the rest continue to the femur near the base of the greater trochanter, at the upper end of the neck. Of the three hip ligaments it is the thinnest and weakest.

Like the other two, the ischiofemoral ligament winds around the neck in a spiral. When the hip straightens, all three twist tighter and screw the femoral head into the socket, so a person can stand with little muscular effort. The ischiofemoral ligament in particular checks medial rotation at the hip in every position, whether the joint is bent, straight or neutral, and it also limits adduction when the hip is flexed.

Because the back of the capsule is less strongly reinforced than the front, posterior dislocation is the usual type of hip dislocation. It typically happens when a bent knee strikes a car dashboard and drives the femoral head backwards out of the socket. In such injuries the sciatic nerve, which lies close behind, may be damaged. Surgeons using a posterior approach for hip replacement cut through this region and often repair the capsule afterwards to lower the risk of dislocation.

Attachments and function

Attaches from

The body of the ischium, behind and below the acetabulum.

Attaches to

The femoral neck near the base of the greater trochanter, with some fibres joining the zona orbicularis.

Function

Checks medial rotation of the hip in all positions, and adduction in flexion; tightens in extension with the other capsular ligaments.

Nerve supply

Articular branches of the nerve to quadratus femoris and of the sciatic nerve.

Blood supply

Branches of the medial circumflex femoral and inferior gluteal arteries.