50A.15.16.Articulations.pdf

ARTICULATIONS

Locations where two or more bones meet, enabling movement and providing structural support for the skeleton.

Joints are composed of:

Bones: The rigid structures that form the skeleton.
Cartilages: Flexible connective tissues that cushion the ends of bones and allow movement at the joint.
Ligaments: Strong bands of connective tissue that connect bones to other bones, providing stability to the joint.
Tendons: Connective tissues that attach muscles to bones, facilitating movement when muscles contract.

Provide mobility to the skeleton, allowing various movements.
Hold the skeleton together, maintaining its shape and integrity.
May offer additional protection to internal organs and structures through cushioning.

Synarthroses: Immovable joints, offering no movement (e.g., sutures in the skull).
Amphiarthroses: Slightly movable joints, allowing limited movement (e.g., pubic symphysis).
Diarthroses: Freely movable joints that permit a wide range of motion (e.g., shoulder and knee).

Fibrous Joints: Bones connected by fibrous tissue with no joint cavity, typically immobile (e.g., sutures).
Cartilaginous Joints: Bones united by cartilage; can be categorized into different types based on the cartilage involved.
Synovial Joints: Bones separated by a fluid-filled cavity, allowing for free movement and flexibility.

These joints are characterized by the absence of a joint cavity and are predominantly fixed or immobile.

Sutures: Interlocking bones most commonly found in the skull, providing protective structure.
Syndesmoses: Bones connected by longer ligaments than sutures, allowing slight movement (e.g., distal tibiofibular joint).
Gomphoses: Peg-in-socket joints, such as teeth fitting into their sockets held by periodontal ligaments.

Sutures: Composed of short fibrous tissue connections, they fuse over time for added protection.
Syndesmosis: Longer ligaments connect bones, providing stability yet allowing for some movement.
Gomphosis: The periodontal ligament serves to hold the teeth firmly in place within their sockets.

Cartilaginous joints lack a joint cavity, and their articulating bones are connected by cartilage.

Synchondroses: Bones joined by hyaline cartilage, often temporary (e.g., epiphyseal plates in growing bones).
Symphyses: Bones united by fibrocartilage, providing strength with some flexibility (e.g., intervertebral discs).

These joints are characterized by a fluid-filled cavity which allows for a wide range of motion.

Articular cartilage: Smooth cartilage that covers the ends of bones, reducing friction during movement.
Synovial cavity: Fluid-filled space that provides lubrication for joint movement and nutrition for articular cartilage.
Articular capsule: Fibrous tissue encasing the joint, adding support and protection.
Synovial membrane: Inner lining of the capsule, producing synovial fluid for lubrication.
Reinforcing ligaments: Strong fibrous tissues that help stabilize joints during movement, preventing dislocation.

Plane Joints: Allow nonaxial movement with gliding actions (e.g., intercarpal joints).
Hinge Joints: Permit uniaxial movement, typically flexion and extension (e.g., elbow joint).
Pivot Joints: Allow uniaxial movement around a central axis (e.g., the joint between the first and second cervical vertebrae).
Condylar Joints: Biaxial movements, allowing flexion, extension, adduction, and abduction (e.g., metacarpophalangeal joints).
Saddle Joints: Allow biaxial movement with a saddle-shaped joint surface (e.g., thumb joint).
Ball-and-Socket Joints: Allow multiaxial movement, providing the greatest range of motion (e.g., shoulder and hip joints).

Gliding: Flat surfaces slide past one another.
Angular Movements: Movements changing the angle between bones, including abduction (movement away from midline), adduction (movement toward midline), flexion (decreasing the angle), and extension (increasing the angle).
Special Movements: Include complex movements such as:
- Supination and Pronation: Rotational movements for the forearm.
- Inversion and Eversion: Movements of the foot; inversion brings the sole inward while eversion moves it outward.
- Elevation and Depression: Movements superiorly (elevation) and inferiorly (depression), like shrugging shoulders.
- Protraction and Retraction: Movement forward (protraction) and backward (retraction), as seen in jaw movements.
- Opposition: Movement of the thumb towards the other fingers.
- Dorsiflexion and Plantar Flexion: Upward (dorsiflexion) and downward (plantar flexion) movements of the foot.
- Lateral Flexion: Bending the torso side to side.

The overall shape of articulating surfaces contributes to joint stability.
The number and positioning of ligaments impact the joint's ability to resist dislocations.
Muscle tone acting on the joint plays a critical role in maintaining its stability, with muscles providing dynamic support during movement.

Cartilage Tears: Damage to the cartilage within a joint, often leading to pain and functional impairment.
Sprains: Injuries to ligaments caused by overstretching or tearing.
Dislocation: A condition where bones are forced out of their normal position, resulting in pain and immobility.

Bursitis: Inflammation of the bursa, typically due to repetitive motion or prolonged pressure, causing pain and swelling.
Tendinitis: Inflammation of tendons, often resulting from overuse injuries, causing pain and reduced function.
Arthritis: A general term for inflammation of joints, leading to pain, swelling, and stiffness, affecting mobility and overall quality of life.