Ch-09-Articulations-handout

Introduction to Articulations

• Bones are designed for support, mobility, and protection.

• Movements are restricted to joints where 2+ bones meet.

• Joints classified based on:

  • Function:

    • Immovable

    • Slightly movable

    • Freely movable

  • Type of movement:

    • Angular

    • Rotational

  • Structural classification:

    • Fibrous (F), Cartilaginous (C), Boney (B)

    • Presence of joint cavity: Synovial (S)

• Joint Stability Factors:

  1. Shape of articular surfaces

  2. Accessory structures

  3. Muscle tone

Functional Classification of Joints

Synarthrosis

• Sutures: Bones interlocked by collagen fibers (F) found only in the skull.

• Gomphosis: Collagen fibers (F) of the periodontal ligament anchor teeth into alveolar sockets (jawbones: maxilla & mandible).

• Synchondrosis: Hyaline cartilage (C) forms a rigid connection between two bones (e.g., 1st sternocostal joint, epiphyseal plates).

• Synostosis: Boney fusion (B) of two or more bones (e.g., coxal bones, epiphyseal lines).

Amphiarthroses

• Syndesmosis: Ligaments (F) connect two bones limiting motion (e.g., distal tibiofibular joint, related to high ankle sprain).

• Symphysis: Bones separated by a wedge or pad of cartilage (e.g., pubic symphysis, intervertebral discs).

Synovial Joint Components

• Joint capsule: Encloses the joint, provides stability.

• Synovial membrane: Lining secreting synovial fluid.

• Articular cartilage: Reduces friction and absorbs shock.

• Joint cavity: Space filled with synovial fluid.

• Accessory structures: Include ligaments, tendons, bursae, fat pads, and meniscus.

Functional Classification – Diarthroses

• Freely Movable Joints: Structurally defined as synovial joints, typically found at the ends of long bones.

• Five Basic Characteristics:

  1. Joint capsules (vascular and innervated)

  2. Joint cavity lined by synovial membrane

  3. Filled with synovial fluid

  4. Articular cartilages of hyaline cartilage

  5. Accessory structures (ligaments, tendons, bursae, etc.)

Types of Movements with Reference to Anatomical Position

Angular Movements

• Flexion / Extension

• Abduction / Adduction

• Circumduction

Rotational Movements

• Pronation / Supination

• Medial (internal) / Lateral (external) rotation

Special Movements

• Dorsiflexion / Plantar flexion

• Inversion / Eversion

• Lateral flexion

• Protraction / Retraction

• Elevation / Depression

• Opposition

Classification of Synovial Joints by Number of Axes

• Plane (nonaxial) joint

• Uniaxial (monaxial):

  • Pivot joint

  • Hinge joint

• Biaxial:

  • Condylar joint

  • Saddle joint

• Multiaxial:

  • Ball-and-socket joint

The Temporomandibular Joint (TMJ)

• Articulation between the condylar process of the mandible and the mandibular fossa of the temporal bone.

• Functions as a modified hinge joint allowing elevation, depression, and lateral excursion.

Intervertebral Articulations

• Stabilized by numerous ligaments: anterior/posterior longitudinal ligaments, ligamentum flavum, etc.

• Vertebral bodies separated by intervertebral discs which includes a nucleus pulposus and anulus fibrosis.

The Shoulder Joint

• Glenohumeral Joint: Comprises the head of the humerus with the glenoid fossa of the scapula.

• Reinforced by various ligaments and muscle tone from surrounding musculature.

• Movements: multiaxial; responsible for a wide range of motion.

The Elbow & Radioulnar Joints

• Elbow: Combination of humeroulnar and humeroradial joints with significant reinforcement by ligaments.

• Radioulnar Joints: Permits pronation and supination.

The Hip Joint

• Strong joint formed by the head of the femur and the acetabulum of the os coxa.

• Reinforced by ligaments and muscle tone of surrounding musculature, allowing a wide range of motion as a ball and socket joint.

The Knee Joint

• Composed of tibial and femoral condyles, and stabilized by several ligaments including patellar and collateral ligaments.

• Movements: primarily flexion/extension, with limited rotation.

The Ankle Joint

• Hinge joint formed by the union of the inferior ends of the tibia and fibula with the talus of the foot.

• Movements: dorsiflexion/plantar flexion and inversion/eversion.

Aging and Articulations

• With age, joints may experience wear and tear leading to conditions like rheumatism and arthritis.

• Arthritis types include Osteoarthritis (OA), Rheumatoid arthritis (RA), and Gouty arthritis - all involving inflammation and damage to articular cartilage.