The Hip Joint

The hip joint is the articulation between the head of the femur and the acetabulum of the hip bone. It is a synovial ball and socket joint.

The stability of the joint is determined by the shape of the articular surfaces (a deep socket securely holding the femoral head), the strength of the joint capsule and associated ligaments, and the insertion of muscles crossing the joint, which tend to be at some distance from the centre of movement. Although the hip is a ball and socket joint, when standing erect the femoral head is not completely covered by the acetabulum, the anterosuperior aspect being exposed.

Joint capsule

The fibrous capsule of the hip is very strong and thicker anteriorly, where the head of the femur articulates, and superiorly, enhancing the stability of the joint. Proximally, the capsule surrounds the acetabulum attaching directly to the bone outside the labrum above and behind, and to the bone and outer edge of the labrum in front and below. Opposite the acetabular notch the capsule attaches to the transverse ligament. On the femur the capsule attaches anteriorly to the intertrochanteric line and to the junction of the neck with the trochanters. Posteriorly the capsule has an arched free border and covers the medial two-thirds of the neck only.

Capsular ligaments



1. The iliofemoral ligament is very strong and thick, being situated anterior to the joint.
2. The pubofemoral ligament strengthens the inferior and anterior aspects of the joint capsule. It runs from the iliopubic eminence and superior pubic ramus to the lower part of the intertrochanteric line.
3. The ischiofemoral ligament, posteriorly, is spiral in shape and arises from the body of the ischium behind and below the acetabulum.

The three ligaments, iliofemoral, pubofemoral and ischiofemoral, have important roles in limiting and controlling the various movements of which the hip is capable.

Inside the capsule



The synovial membrane of the hip joint lines the fibrous capsule and covers the:
• Neck of the femur between the attachment of the fibrous capsule and the edge of the articular cartilage of the head
• Nonarticular area of the acetabulum, providing a covering for the ligament of the femoral head.

A synovial protrusion beyond the free margin of the fibrous capsule onto the posterior aspect of the femoral neck forms a bursa for the obturator externus tendon.
The ligament of the head of the femur (Ligamentum teres) is weak and of little importance in strengthening the hip joint. Its wide end attaches to the margins of the acetabular notch and the transverse acetabular ligament. Its narrow end attaches to the pit in the head of the femur. Usually the ligament contains a small artery to the head of the femur.

The fat pad in the acetabular fossa (covered with synovial membrane) fills the part of the acetabular fossa that's not occupied by the femoral head. The malleable nature of the fat pad permits it to change shape to accommodate the varying shape of the head during joint movements.

Blood Supply of the Hip Joint



The arteries supplying the hip joint are:
• Medial and lateral circumflex femoral arteries: usually branches of the deep artery of the thigh but occasionally arising as branches of the femoral artery
• Artery to the head offemur--a branch of the obturator artery--enters through the ligament of the head.

Nerve Supply of the Hip Joint

• Femoral nerve or its muscular branches (anteriorly)
• Accessory obturator nerve, if present (anteriorly)
• Obturator nerve (anterior division) (inferiorly)
• Superior gluteal nerve (superiorly and posteriorly)
• Nerve to quadratus femoris (posteriorly).

Movements of the Hip Joint

Abduction, Adduction, Flexion, Extension, External and Internal rotation

Normal angles

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