Joints Classification. Movements

Periosteum and Bone Marrow

  • Periosteum

    • A dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints.

  • Yellow Bone Marrow

    • A type of bone marrow that primarily stores fat and serves as an energy reserve.

Joint Structure and Components

  • Fibrous Layer

    • A layer of the articular capsule providing structural strength to the joint.

  • Synovial Membrane

    • The inner lining of the joint capsule that produces synovial fluid.

  • Joint Cavity

    • The space between articulated bones, filled with synovial fluid.

  • Articular Capsule

    • Capsule that encloses the joint, containing synovial fluid to lubricate the joint space.

  • Articular Cartilage

    • Smooth tissue covering the ends of bones, providing a low-friction surface for joint movement.

  • Extrinsic Ligament

    • Ligament located outside the joint capsule providing additional instability and support.

Classification of Joints

  • Types of Joints

    • Fibrous Joint

    • Cartilaginous Joint

    • Synovial Joint

Joint Movements

  • Movements in Synovial Joints

    • Various types, including gliding, angular, rotational, and special movements.

Learning Objectives of the Lecture

  • Students should be able to describe:

    • Types of joint classification (fibrous, cartilaginous, synovial).

    • Movements within Synovial Joints including gliding, angular, rotational, and special movements.

    • Applications of bioengineering principles in joint replacements.

    • Metrics for engineering success in joint replacement technology.

Definitions of Joints and Their Study

  • Joints (Articulations)

    • Points of union between bones, cartilage, or teeth.

    • The study of joints is called Arthrology, important for bioengineers in the design of prosthetic implants that replicate natural joint function.

  • Structural Classes of Joints

    • Fibrous Joint: Connected by dense connective tissue,

    • Cartilaginous Joint: Bones joined by cartilage,

    • Synovial Joint: Bones joined by ligaments with a fluid-filled cavity.

Functional Classification of Joints

  • Functional Classes:

    1. Synarthroses: Immobile joints, can be fibrous or cartilaginous.

    2. Amphiarthroses: Slightly mobile joints, can be fibrous or cartilaginous.

    3. Diarthroses: Freely mobile joints, all synovial joints.

Further Classification of Joints by Structure

  • Fibrous Joints

    • No joint cavity; include gomphosis, suture, and syndesmosis.

  • Cartilaginous Joints

    • Lack a joint cavity; include synchondrosis and symphysis.

  • Synovial Joints

    • Joint cavity present; categorized as diarthroses.

Types of Fibrous Joints

  • Gomphoses

    • “Peg in a socket” joint; articulation of teeth with mandible/maxilla; held by periodontal ligaments.

  • Sutures

    • Found between skull bones; short fibers interlocking and stabilizing structure, allowing growth in childhood.

  • Syndesmoses

    • Bound by interosseous membrane; allows slight mobility between bones like tibia and fibula.

Types of Cartilaginous Joints

  • Synchondroses

    • Bones joined by hyaline cartilage; entirely immobile (e.g., epiphyseal plate).

  • Symphyses

    • Fibrocartilage pads between bones to resist compression and allow slight mobility.

Properties of Synovial Joints

  • Bones are separated by an articular cavity.

  • Comprised of several common features:

    1. Articular capsule

    2. Joint cavity

    3. Synovial fluid

    4. Articular cartilage

    5. Associated structures: ligaments, nerves, and blood vessels.

  • Bioengineered designs aim to replicate these features.

Classification of Synovial Joints by Movement

  • Types of Movements:

    1. Uniaxial: Movement in one plane (e.g., hinge joints).

    2. Biaxial: Movement in two planes (e.g., condylar joints).

    3. Multiaxial or Triaxial: Movement in multiple planes (e.g., ball-and-socket joints).

Movements of Synovial Joints

1. Gliding Motion

  • Opposing surfaces slide back-and-forth or side-to-side, typically occurs in plane joints (e.g., carpals).

2. Angular Motion

  • Changes the angle between two bones; includes:

    • Flexion: Decreases angle, bringing bones closer (e.g., bending a finger).

    • Extension: Increases angle between bones (e.g., straightening fingers).

    • Abduction: Movement away from midline (e.g., lifting arm laterally).

    • Adduction: Movement toward midline (e.g., lowering arm).

    • Circumduction: Circular movement, creating a cone shape (e.g., drawing circles).

3. Rotational Motion

  • Bone pivots around its longitudinal axis:

    • Lateral Rotation: Moving anterior surface laterally.

    • Medial Rotation: Moving anterior surface medially.

    • Pronation and Supination: Rotational movements of the forearm.

4. Special Movements

  • Depression: Inferior movement (e.g., opening mouth).

  • Elevation: Superior movement (e.g., closing mouth).

  • Dorsiflexion: Flexing ankle to bring foot upward.

  • Plantar Flexion: Pointing toes downward.

  • Eversion and Inversion: Side movements of the foot, turning sole in or out.

  • Protraction and Retraction: Grappling jaw movements.

  • Opposition and Reposition: Thumb movement toward fingers or away.