Supports of the Hip Joint

1. Bony Support (Articular Surfaces)

• The lunate surface of the acetabulum (covered by hyaline cartilage, broadest superiorly) receives the spherical head of the femur.
• The acetabulum almost entirely encompasses the femoral head, contributing substantially to inherent bony stability.
• The nonarticular acetabular fossa contains loose connective tissue and the ligament of the head.

2. Acetabular Labrum

• A fibrocartilaginous collar that deepens the acetabulum and grips the femoral head, further improving stability.
• Inferiorly, it bridges the acetabular notch as the transverse acetabular ligament, converting the notch into a foramen.

Fig. 6.31 - Transverse acetabular ligament (A) and ligament of the head of femur (B). Gray's Anatomy for Students

3. Joint Capsule (Fibrous Membrane)

• A strong, thick fibrous membrane that encloses the joint.
• Medial attachment: margin of the acetabulum, transverse acetabular ligament, and adjacent margin of the obturator foramen.
• Lateral attachment: intertrochanteric line anteriorly; just proximal to the intertrochanteric crest posteriorly (so the posterior femoral neck lies intracapsular).
• The capsule contains zona orbicularis fibers (circular fibers that form a collar around the femoral neck, helping grip the neck).

4. Synovial Membrane

• Lines the fibrous membrane and attaches to the margins of articular surfaces.
• Forms a tubular sleeve around the ligament of the head of femur.
• From its attachment at the margin of the femoral head, it covers the femoral neck before reflecting onto the fibrous membrane - this is clinically important because it carries retinacular vessels supplying the femoral head.

Fig. 6.32 - Synovial Membrane of the Hip Joint. Gray's Anatomy for Students

5. Ligaments

Fig. 6.33 - (A) Fibrous membrane, (B) Iliofemoral and pubofemoral ligaments - anterior view, (C) Ischiofemoral ligament - posterior view. Gray's Anatomy for Students

a. Iliofemoral Ligament (Ligament of Bigelow)

• Strongest ligament in the body - Y-shaped (inverted Y)
• Position: Anterior to the hip joint
• Proximal attachment: Ilium between the anterior inferior iliac spine (AIIS) and the margin of the acetabulum
• Distal attachment: Along the intertrochanteric line of the femur (thicker superiorly and inferiorly, giving the Y shape)
• Function: Resists extension and lateral rotation; prevents the pelvis from tilting backward during standing (reduces muscle effort)

b. Pubofemoral Ligament

• Position: Anteroinferior to the hip joint
• Proximal attachment: Iliopubic eminence, adjacent bone, and obturator membrane
• Distal attachment: Blends with the fibrous membrane and deep surface of the iliofemoral ligament
• Function: Limits abduction and extension

c. Ischiofemoral Ligament

• Position: Posterior to the hip joint (weakest of the three)
• Medial attachment: Ischium, just posteroinferior to the acetabulum
• Lateral attachment: Greater trochanter, deep to the iliofemoral ligament
• Function: Limits extension and medial rotation

d. Ligament of the Head of Femur (Ligamentum Teres)

• A flat band of delicate connective tissue inside the joint
• Attaches from the fovea on the femoral head to the acetabular fossa, transverse acetabular ligament, and margins of the acetabular notch
• Limited mechanical role in adults; carries a branch of the obturator artery (contributing to blood supply of the femoral head in children)

6. Muscle Support

7. Vascular Supply

• Medial and lateral circumflex femoral arteries (main supply to femoral head)
• Obturator artery (acetabular branch via ligamentum teres)
• Superior and inferior gluteal arteries
• First perforating branch of the deep femoral artery

8. Nerve Supply (Hilton's Law)

• Femoral nerve
• Obturator nerve
• Superior gluteal nerve
• Nerve to quadratus femoris