Joints and Joint Movement

Joints and Joint Movements

Bones of the Appendicular Skeleton: This lecture focuses on the second part of the appendicular skeleton and its joints.

Connection of Bones: The adult human body has 206 bones. All, except the hyoid bone, connect to at least one other bone.
Definition of Joints: Joints are the points where two or more bones meet. Their stability and movement are inversely related. Joints can allow for smooth movement, or may restrict motion for stability.
Importance: Understanding joint structure and function aids in identifying joint types in different body regions.

Structural Classification:
- Fibrous Joints: Adjacent bones connected by fibrous connective tissue.
- Cartilaginous Joints: Joined by hyaline cartilage or fibrocartilage.
- Synovial Joints: Articulating surfaces not directly connected but move against each other within a lubricated joint cavity.
Functional Classification:
- Synarthrosis: Immobile joints (e.g., sutures in the skull).
- Amphiarthrosis: Slightly movable joints (e.g., intervertebral discs).
- Diarthrosis: Freely movable joints (e.g., synovial joints).

Example: Sutures of skull - classified as fibrous joints for structural classification.
- Function: Provides strong union to protect the brain.

Examples:
- Intervertebral discs: Cartilaginous joints that allow limited mobility, providing flexibility for bending and twisting.
- Pubic symphysis: Connects pubic regions of hip bones, allowing limited movement and contributes to pelvic stability.

Definition: This category includes all synovial joints, which offer the greatest range of movement.
Classification:
- Uniaxial: Allows movement in one direction (e.g., elbow).
- Biaxial: Movement in two directions (e.g., metacarpophalangeal joint).
- Multiaxial: Movement in three dimensions (e.g., shoulder and hip joints).

Definition: Strong bands of fibrous tissue connecting bones.
Function: Provide stability and restrict excessive movements.
Types:
- Extrinsic: Located outside articular capsule.
- Intrinsic: Incorporated into articular capsule.
- Intracapsular: Found inside articular capsule.

Categories Based on Movement:
- Pivot Joint: Allows rotation (e.g., between cervical vertebrae).
- Hinge Joint: Permits bending (e.g., elbow).
- Saddle Joint: Biaxial joint allowing diverse motion (e.g., thumb).
- Plane Joints: Allow gliding movements (e.g., between tarsal bones).
- Condyloid Joint: Allows movement in two planes (e.g., wrist joint).
- Ball and Socket Joint: Greatest range of motion (e.g., hip and shoulder).

Definition: Inflammation of joints causing pain and reduced mobility.
Types:
- Osteoarthritis: Most common; degenerative joint disease resulting from wear and tear.
- Rheumatoid Arthritis: An autoimmune disorder attacking joint tissues.

Causes: Risks include joint injury, labor-intensive jobs, physical activity, and obesity.
Symptoms: Pain, swelling, stiffness, and reduced mobility. No cure, but treatments available (e.g., lifestyle changes, medications, surgery).

Characteristics: Immune system attacks joint structures, causing significant damage and disability. Symptoms include joint swelling, pain, and deformity.

Flexion and Extension: Movements in the sagittal plane; flexion decreases angle while extension increases it.
Hyperflexion and Hyperextension: Excessive movements that can lead to injury.
Abduction and Adduction: Lateral movements in the coronal plane.
Circumduction and Rotation: Circular movements and twisting around an axis.
Pronation and Supination: Movements of the forearm; supination is palm up, pronation is palm down.
Dorsiflexion and Plantar Flexion: Movements of the ankle, with dorsiflexion lifting the foot and plantar flexion pointing toes down.
Inversion and Eversion: Movements of the foot; inversion turns the foot inward while eversion turns it outward.
Protraction and Retraction: Movements of the scapula and mandible.
Depression and Elevation: Movements of the scapula and mandible.
Opposition and Reposition: Thumb movements unique to human anatomy.