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Head of femur

The head of the femur is the smooth, rounded, proximal articular surface of the femur that articulates with the acetabulum of the pelvis to form the hip joint. It represents approximately two-thirds of a sphere, providing stability while allowing extensive mobility.

The head is covered almost entirely with hyaline articular cartilage, except for the fovea capitis femoris, a small depression where the ligamentum teres (ligament of the head of femur) attaches. This ligament carries a small artery (artery to the head of the femur from the obturator artery), though the primary vascular supply arises from the medial and lateral circumflex femoral arteries (branches of the profunda femoris artery).

The head of femur plays a key role in weight transmission, mobility, and stability of the hip joint. Its vascular anatomy is clinically important, as disruption (e.g., femoral neck fracture, hip dislocation) can cause avascular necrosis (AVN).

Synonyms

  • Femoral head

  • Caput femoris

Function

  • Articulates with the acetabulum to form the hip joint

  • Transmits body weight from pelvis to femoral shaft during standing and gait

  • Covered with hyaline cartilage for smooth articulation and shock absorption

  • Attachment site for ligamentum teres at the fovea capitis

Nerve Supply (joint capsule and surrounding structures)

  • Femoral nerve (articular branches)

  • Obturator nerve (posterior branch)

  • Accessory obturator nerve (when present)

  • Sciatic nerve (minor posterior articular contribution)

Arterial Supply

  • Medial circumflex femoral artery (retinacular branches – dominant supply)

  • Lateral circumflex femoral artery (contributes via anterior retinacular branches)

  • Artery of ligamentum teres (branch of obturator artery – minor in adults, important in children)

Venous Drainage

  • Follows arterial pathways: circumflex femoral veins → profunda femoris vein → femoral vein

MRI Appearance

T1-weighted images:

  • Bone cortex: hypointense (dark rim)

  • Bone marrow: high to intermediate signal (fatty marrow)

  • Cartilage: intermediate signal

  • Useful for marrow infiltration, fractures, and AVN (early stage shows decreased signal)

T2-weighted images:

  • Cortex: hypointense

  • Marrow: intermediate to bright depending on water/fat content

  • Cartilage: hyperintense smooth layer

  • AVN shows the classic double-line sign (inner bright line, outer dark line)

PD Fat-Saturated (Proton Density with Fat Suppression):

  • Cortex: hypointense

  • Marrow edema: hyperintense signal (seen in trauma, AVN, arthritis)

  • Excellent for detecting cartilage defects, labral tears, and subchondral edema

STIR:

  • Suppresses fat, making bone marrow edema, fractures, and early AVN conspicuous as bright hyperintensity

  • Sensitive for detecting acute trauma and inflammatory processes

T1 Post-Gadolinium (with fat saturation):

  • Normal marrow: mild homogeneous enhancement

  • Pathology: AVN shows rim enhancement, tumors and infection show heterogeneous enhancement

  • Outlines synovitis, vascularized granulation tissue, or neoplasms

3D T2-weighted Imaging:

  • Cortex: hypointense

  • Provides high-resolution multiplanar evaluation of femoral head shape, cartilage coverage, and acetabular congruency

  • Essential for FAI (cam deformity) and surgical planning

CT Appearance

Non-contrast CT:

  • Bone cortex: hyperdense and well-demarcated

  • Marrow: lower density compared to cortex

  • Excellent for detecting subchondral fractures, sclerotic changes, cam lesions, and bone loss

CT Post-Contrast:

  • Bone: cortex remains unchanged

  • Soft tissue and synovium: enhancement reveals infection, tumor, or synovitis

  • Occasionally used for evaluating vascular compromise or intra-articular pathology when MRI contraindicated

CT VRT 3D image

Head of femur 3D CT VRT anatomy image

CT image

Head of femur ct axial image

MRI image

Head of femur MRI axial anatomy image