Understanding Joints: Types, Functions, and Movements

Joint

A point where two or more bones meet.

Functions of joints

To connect bones and to allow movement.

Functional classifications of joints

Synarthroses, amphiarthroses, and diarthroses.

Structural classifications of joints

Fibrous joints, cartilaginous joints, and synovial joints.

Example of functional and structural classification of joint

Synarthrosis—suture; amphiarthrosis—pubic symphysis; diarthrosis—shoulder.

Material connecting bones in fibrous joints

Collagen fibers.

Sutures location in the body

Between bones of the skull.

Bones connected by gomphoses

Teeth and their sockets.

Bones connected by syndesmoses

Radius and ulna, tibia and fibula.

Movement allowed at fibrous joints

Little to no movement.

Material connecting bones in cartilaginous joints

Cartilage.

Examples of synchondroses

Epiphyseal plate and the joint between rib 1 and the sternum.

Examples of symphyses

Intervertebral discs and pubic symphysis.

Synchondroses after ossification

Synostoses.

Defining feature of synovial joints

A joint cavity filled with synovial fluid.

Structures part of a typical synovial joint

Articular cartilage, joint cavity, synovial fluid, articular capsule, ligaments, nerves, and blood vessels.

Function of synovial fluid

Reduces friction and nourishes cartilage.

Role of the articular capsule in a synovial joint

Encloses the joint cavity and maintains the joint's integrity.

Role of nerves and blood vessels in a synovial joint

Nerves detect pain and monitor joint position; blood vessels provide nutrients.

Bursa

A fluid-filled sac that reduces friction between tissues.

Tendon sheath

An elongated bursa that wraps around a tendon.

Difference between bursae/tendon sheaths and ligaments/tendons

They reduce friction but do not provide structural support.

Plane joint

Gliding.

Hinge joint

Flexion and extension.

Pivot joint

Rotation.

Condylar joint

Flexion, extension, abduction, and adduction.

Saddle joint

Flexion, extension, abduction, and adduction.

Ball-and-socket joint

Movement in all directions.

Gliding movement

A sliding motion between flat bone surfaces.

Angular movement

A change in the angle between two bones.

Rotational movement

A bone turning around its own axis.

Flexion

A movement that decreases the angle between bones.

Abduction

A movement away from the midline.

Circumduction

A circular motion of a limb.

Medial rotation

Rotation toward the midline.

Pronation

Rotation of the forearm so the palm faces downward.

Plantarflexion

Movement that points the toes downward.

Inversion

Turning the sole of the foot inward.

Protraction

Moving a body part forward.

Elevation

Lifting a body part upward.

Opposition

Movement of the thumb toward the fingers.

Joint stability and mobility relationship

As mobility increases, stability decreases.

Highly mobile joint that lacks stability

The shoulder joint.

Cartilage tear causes

Trauma or overuse.

Bursitis causes

Inflammation of a bursa due to friction or injury.

Tendonitis causes

Inflammation of a tendon or tendon sheath from overuse.

Sprain vs dislocation

A sprain is a stretched or torn ligament; a dislocation is a misalignment of bones.

Osteoarthritis

Degeneration of articular cartilage from wear and tear.

Rheumatoid arthritis

An autoimmune disease that attacks synovial joints.

Gouty arthritis

A buildup of uric acid crystals in the joints.