ANAT 6.2 - Updated

Evolutionary/Biomechanical Adaptations for humans

Humans are adapted for bipedal stance:

• pelvis rotated laterally

• illium (pelvic wing) curves down sides

This allows:

• muscles on lateral hip

• hip abductors to stabilise pelvis

• standing on one leg during walking

Without these abductors:

• pelvis would drop during single-leg stance

Line of gravity:

• passes posterior to hip & anterior to knees (promotes hip and knee extension)

  • extended joints allow ligaments/joints to support posture & muscles to relax more

Components of the pelvic girdle and its function

• Right pelvic bone

• Left pelvic bone

• Sacrum

Function: transfers force btw axial skeleton and lower limbs

Pelvic bone structure:

Each pelvic bone forms from fusion of ilium, ischium and pubis

Male vs Female Pelvis

Female: wider, shorter, larger infrapubic angle (adaptations for childbirth)

Male: narrower, taller, smaller pubic angle

What’s a Sacroiliac Joint (SI Joint) and its role?

Synovial plane joint btw Sacrum and ilium

• does very small gliding

• main role is to tranfer force and for stability

What are the 3 strong stabilising ligaments and role?

• sacroiliac ligaments

• sacrotuberous ligament

• sacrospinous ligament

These resist sacral tilting under body weight.

What’s the pubic symphysis?

Secondary cartilaginous joint between pubic bones.

• contains fibrocartilage disc

• function is for stability and movement

What’s the femur and role?

Femur is the largest bone in body.

Role is to bear weight.

Hip joint:

• is a synovial ball and socket joint

• has deep socket and large femoral head = very stable

• Ligaments that stabilise it are iliofemoral, ischiofemoral and pubofemoral ligaments

Overall makes it less mobile but more stable that shoulder joint.

Tibia vs Fibula

Tibia

• large

• medial

• major weight-bearing bone

Fibula

• thin

• lateral

• mainly muscle attachment + ankle support

Important Tibia/Fibula Landmarks

Landmark	Notes
Tibial tuberosity	quadriceps attachment
Medial malleolus	medial ankle bump
Lateral malleolus	lateral ankle bump

Osgood-Schlatter Disease

Inflammation near tibial tuberosity from quadriceps pulling during growth.

What joints does knee joint contain?

Actually contains:

1. Tibiofemoral joint

2. Patellofemoral joint

Type:

• modified hinge synovial joint

Main movements:

• flexion

• extension

Additional movement:

• rotation when flexed

Types, functions and shape of Menisci

Types:

• medial meniscus

• lateral meniscus

Functions:

• improve joint congruency

• shock absorption

• distribute synovial fluid

Shape:

• flat inferiorly

• curved superiorly

Knee Ligaments

Ligament	Prevents
MCL	valgus stress
LCL	varus stress

Valgus

Knee collapses inward.

Varus

Knee bows outward.