The pelvis and the hip (joints)

Characteristics of the hip joint

• Synovial

• Enarthrosis (ball and socket). 2/3 of the ball fitted in the acetabulum

• Multiaxial

Pelvic girdle joints

• sacroiliac joint

• coxofemoral joint

• Pubic symphysis

Characteristics of the femur head

it has depression on top of it which is called the fovea for the ligament of the head of the femur.

Except for the fovea, the femoral head is also covered entirely in articular cartilage which facilitates smooth movement and prevents bone erosion as it slides within the acetabulum.

Acetabulum

Bowl shape structure formed by the fusion of:

• Ilium

• Ischium

• Pubis

Acetubular labrum

increases the surface area of the acetabulum to allow more than half of the femoral head to fit within the acetabulum for stability.

Fibrous capsule and synovial membrane

• fibrous capsule: strong joint capsule formed by an external fibrous layer,

• synovial membrane : internal layer.

Ligaments of the hip

• Intracapsular

• Capsular

Capsular ligaments

• Iliofemoral

• Pubofemoral (anterior)

• Ischiofemoral (posterior)

Most of these ligaments’ fibers has an spiral shape

Iliofemoral ligament

Origin: anterior inferior iliac spine (AIIS) of the pelvis and acetubular margin

Insertion: intertrochanteric line of the femur.

This ligament is the strongest ligament of the hip joint (and of the body), providing stability and preventing hyperextension.

Pubofemoral ligament (anterior)

Origin: pectineal crest and pectineal pubis
Insertion: intertrochanteric line

Ischiofemoral ligament (posterior)

Origin : ischium

Insertion : intertrochanteric line (not crest)

limits internal rotation

Synovial layer

• Covers the ligementum teres (ligament of the head of the femur) and acetabular fossa producing synovial fluid to lubricate the joint.

Retinacula of the synovial membrane

Vascular plexus for the femoral head

Intracapsular ligaments

• Transverse acetabular ligament

• Ligamentum teres

Ligamentum teres

• ligament of the head of the femur, which houses the artery to the head of the femur, a branch of the obturator artery.

Origin: margins of the acetabular notch along with the transverse acetabular ligament,

Transverse acetabular ligament

attaches to the edges of the acetabular notch

Movements of the hip

• Flexion-extension

• abduction-adduction

• rotation, medial (internal) and lateral (external)

• circumduction (combination of previous movements)

Sacroiliac joint type

synovial type.

primarily responsible for transferring weight and forces between the upper body and lower limbs.

Articular surfaces of the sacrum and ilium

• Flat with irregularities

• Cartilage is thick

Ligaments of the sacroiliac joint

• anterior

• interosseous

• posterior

Accesory ligaments of the sacroiliac joints

• sacrospinous

• sacrotuberous

interosseous sacroiliac joint

A type of joint connection between the sacrum and ilium, characterized by strong ligaments that stabilize the pelvis during movement.

Sciatic foramina

• Greater sciatic foramen

• Lesser sciatic foramen

Static foramina

The sciatic foramina are two openings in the posterior pelvis that allow important nerves, vessels, and muscles to pass between the pelvis and gluteal region. They are formed by the greater and lesser sciatic notches of the pelvis and the sacrospinous and sacrotuberous ligaments.

Greater and lesser sciatic foramen

• greater: from lesser pelvis to gluteal region

• lesser: from perineum to gluteal region

Movements of the pelvis

Important during pregnancy.

Relaxin hormone that helps in pelvic flexibility, relaxing the ligaments

• Nutation: standing, the coccyx goes backwards

• counter-nutation

Pubic symphysis

The pubic symphysis is a cartilaginous joint located between the left and right pubic bones in the pelvis, providing slight movement and stability during activities such as walking and childbirth.

Pubic symphysis articular surfaces

• flat but with reciprocal ridges and papillae

Pubic symphysis

• hyalinge cartilage → dark blue

• interpubic disc (fibrocartilagenous, shock absorber, not synovial) → light blue

• Superior and inferior (arcuate) ligament → red