Anatomy of Joints: Types, Movements, and Functions

Fibrous joints

Little to none (immovable or slightly movable).

Cartilaginous joints

Slightly movable.

Synovial joints

Freely movable (diarthrosis).

Synarthrosis

An immovable joint (e.g., gomphosis, synchondrosis).

Amphiarthrosis

A slightly movable joint (e.g., syndesmosis, symphysis).

Diarthrosis

A freely movable joint (all synovial joints).

Gomphosis joint

Tooth in its alveolar socket.

Synchondrosis joint

Epiphyseal plate (growth plate).

Syndesmosis joint

Distal joint between tibia and fibula.

Symphysis joint

Pubic symphysis.

Articular cartilage function

Covers bone ends, reduces friction, absorbs shock.

Layers of articular capsule

Outer fibrous layer and inner synovial membrane.

Synovial fluid production

Synoviocytes in the synovial membrane.

Components of synovial fluid

Filtrate of plasma with hyaluronic acid, glycoproteins, and lubricin.

Function of menisci

Cushion and stabilize the joint (e.g., knee).

Bursae

Small sacs that reduce friction between bone and soft tissue.

Tendon sheaths

Tube-like bursae surrounding tendons in high-friction areas.

Factors affecting ROM

Bone shape, ligament tension, and muscle arrangement.

Hormones effect on joints

Relaxin increases flexibility (e.g., during childbirth).

Disuse of a joint

Atrophy and reduced synovial fluid production.

Plane joint movement

Gliding (nonaxial).

Hinge joint movement

Flexion and extension (uniaxial).

Pivot joint movement

Rotation (uniaxial).

Condyloid joint movement

Flexion/extension, abduction/adduction (biaxial).

Saddle joint movement

Angular movement (biaxial, e.g., thumb).

Ball-and-socket joint movement

All directions (multiaxial).

Flexion vs extension

Flexion decreases angle; extension increases it.

Abduction vs adduction

Abduction moves away; adduction moves toward midline.

Rotation

Turning around bone's axis.

Circumduction

Circular movement combining flexion, extension, abduction, adduction.

Supination vs pronation

Supination turns palm up; pronation turns palm down.

Inversion vs eversion

Inversion turns sole inward; eversion turns it outward.