Topics

Topic

design image
Articular capsule of hip joint

The articular capsule of the hip joint is a strong, fibrous sleeve that surrounds the hip joint, enclosing the femoral head and acetabulum. It provides stability, resists excessive motion, and contains synovial fluid to nourish and lubricate the joint. The capsule is reinforced by thick ligaments and blends with surrounding musculature, making it crucial for both mobility and stability of the hip.

Synonyms

  • Hip joint capsule

  • Capsular ligament of the hip

  • Fibrous capsule of hip

Attachments

  • Proximally (pelvic side):

    • Outer margin of the acetabulum

    • Acetabular labrum

    • Transverse acetabular ligament

  • Distally (femoral side):

    • Intertrochanteric line (anteriorly)

    • Neck of femur (posteriorly, just proximal to intertrochanteric crest)

Structure and Relations

  • Fibrous layer: Thick and strong, reinforced by ligaments (iliofemoral, pubofemoral, ischiofemoral)

  • Synovial layer: Inner lining that secretes synovial fluid and extends to cover femoral neck

  • Relations:

    • Anteriorly: Iliopsoas muscle and femoral nerve/vessels

    • Posteriorly: Obturator externus, quadratus femoris, sciatic nerve (more superficial)

    • Superiorly: Gluteus minimus, reflected head of rectus femoris

    • Inferiorly: Obturator externus and acetabular margin

Nerve Supply

  • Supplied by articular branches from:

    • Femoral nerve

    • Obturator nerve

    • Sciatic nerve

    • Superior gluteal nerve

Arterial Supply

  • Medial and lateral circumflex femoral arteries

  • Obturator artery (acetabular branch)

  • Superior and inferior gluteal arteries

Venous Drainage

  • Follows arterial supply into femoral, obturator, and gluteal veins

Function

  • Encloses and stabilizes the hip joint

  • Resists dislocation while allowing wide range of motion

  • Maintains negative intra-articular pressure, contributing to joint congruence

  • Provides proprioceptive input for joint position and movement

Clinical Significance

  • Injured in hip dislocations and labral tears

  • Thickening or synovial inflammation may occur in arthritis or synovitis

  • Hip capsule contracture contributes to restricted motion in degenerative disease

  • Surgical reference in hip arthroscopy and total hip arthroplasty

MRI Appearance

T1-weighted images:

  • Capsule appears as a thin low-signal band around hip joint

  • Surrounding fat planes are bright, aiding visualization

T2-weighted images:

  • Capsule remains low signal

  • Joint effusion or synovitis appears as bright intra-articular fluid

  • Thickened or pathological capsule may show intermediate to high signal

STIR (Short Tau Inversion Recovery):

  • Capsule normally low signal

  • Inflammation, edema, or capsular strain: bright hyperintensity

  • Fluid collections: also appear bright

T1 Fat-Sat Post-Contrast:

  • Capsule may show thin uniform enhancement due to vascular synovium

  • Synovitis or arthropathy: thickened and strongly enhancing capsule

  • Abscess: rim enhancement with non-enhancing center

CT Appearance

Non-Contrast CT:

  • Capsule not clearly visualized unless thickened or calcified

  • Hip joint effusion appears as soft tissue density widening the joint space

Post-Contrast CT:

  • Capsule itself enhances poorly, but synovial lining enhances with contrast

  • Capsular thickening or enhancing synovium seen in arthritis, tumor, or infection

  • Effusions/abscesses show low attenuation with rim enhancement

MRI image

articular capsule of hip joint MRI axial anatomy image-img-00000-00000

MRI image

articular capsule of hip joint MRI sag anatomy image-img-00000-00000_00001

MRI image

articular capsule of hip joint MRI axial anatomy image-img-00000-00000

MRI image

Ischiofemoral ligament MRI coronal anatomy image-img-00000-00000

MRI image

Ischiofemoral ligament MRI coronal anatomy image-img-00000-00000