Chapter 14

Chapter 14: Articulations

Introduction

  • Articulation: Point of contact between bones.

  • Joints: Mostly movable but can be immovable or allow limited motion.

  • Movable joints facilitate complex, coordinated, purposeful movements.

Classification of Joints

  • Joints can be classified by structural or functional criteria.

Structural Classification

  • Based on the presence of a fluid-filled joint capsule or type of connective tissue:

    • Synovial Joints: Contain a fluid-filled joint capsule.

    • Fibrous Joints (synarthrodial): Bones connected by connective tissue.

    • Cartilaginous Joints (amphiarthrodial) : Bones connected by cartilage.

Functional Classification

  • Based on degree of movement allowed:

    • Synarthroses: Immovable joints.

    • Amphiarthroses: Slightly movable joints.

    • Diarthroses: Freely movable joints.

Structural Classification Cont.

Fibrous Joints (Synarthroses)

  • Little to no movement; bones fit closely together.

    • Syndesmoses: joints in which ligaments connect two bones.

    • Sutures: Interlocking teethlike projections in the skull that interlock.

    • Gomphoses: Joint between a tooth and the alveolar process of mandible or maxilla.

Cartilaginous Joints (Amphiarthroses)

  • Joined by hyaline cartilage or fibrocartilage; allow limited movement.

    • Synchondroses: Hyaline cartilage present between articulating bones (e.g., ribs to sternum).

    • Symphyses: Fibrocartilage pad or disk connects bones (e.g., pubic symphysis).

Synovial Joints (Diarthroses)

  • Freely movable joints with specific structures:

    • *Joint Capsule: Sleevelike casing around ends of bones that binds them together.

    • *Synovial Membrane: Lines joint capsule and secretes synovial fluid.

    • *Articular Cartilage: Hyaline cartilage on articulating surfaces of bones.

    • *Joint Cavity: Space between bones.

    • *Menisci (articular disks): Pads of fibrocartilage between articulating bones.

    • Ligaments: Dense fibrous tissue holding bones together.

    • Bursae: Synovial fluid-filled sacs for cushioning.

Types of Synovial Joints

Uniaxial Joints

  • Movements around one axis and one plane:

    • Hinge Joints: Allow flexion and extension like a door (e.g., elbow).

    • Pivot Joints: Allow rotation left and right (e.g. axis and atlas of vertebral column). projection of one bone articulates with a ring or notch of another bone.

Biaxial Joints

  • Movements around two axes:

    • Saddle Joints: Resemble saddles; notably in the thumb.

    • Condyloid (Ellipsoidal) Joints: Condyle fits into an elliptical socket.

Multiaxial Joints

  • Movements around three or more axes:

    • Ball-and-Socket Joints (spheroid): Most movable joints that can move in all planes, ball-shaped head of one bone fits into a concave depression of the other (e.g., shoulder, hip).

    • Gliding Joints: Flat surfaces allow smooth and continuous gliding movements along various axes (e.g., between vertebrae).

Representative Synovial Joints

Humeroscapular Joint (Shoulder)

  • Highly mobile due to shallow glenoid cavity; stability from ligaments and muscles.

Elbow Joint

Composed of the humeroradial and humeroulnar joints; classic hinge joint functioning.

Proximal Radioulnar Joint

between head of radius and medial notch of ulna

Distal radioulnar joint

point of articulation between the ulnar notch of the radius and the head of the ulna

Radiocarpal (wrist) joints

Intercarpal Joints

Carpometacarpal joints

Metacarpophalangeal joints

Interphalangeal joints

Hip joint

Knee Joint

Ankle Joint

  • Synovial hinge joint; common site for sprains.

Vertebral Joints

  • Connected by ligaments and intervertebral disks.

Types and Range of Movement at Synovial Joints

Range of Motion Assessment

  • Used to assess joint injury, typically done with a goniometer.

  • ROM can be measured actively or passively

  • Key movements include:

    • Flexion: Decreasing angle.

    • Extension: Increasing angle back to original position.

    • Hyperextension: stretching or extending a body part beyond its anatomical position

    • Abduction/Adduction: Moving away from (abduction) or toward the median plane (adduction).

    • Internal/External Rotation: Rotating limb toward or away from the body.

    • Elevation/Depression: Moving body parts up or down.

    • Dorsi Flexion:

      • Movement where the toes are pointed towards the shin (dorsiflexion)

    • Plantar Flexion:

      • Involves moving the foot in a downward direction (plantar flexion).

        include bullet points for circular and gliding movements

Circular Movements:

  • Rotation: Turning a bone around its own axis.

  • Circumduction: Circular movement of a limb that outlines a cone shape.

Gliding Movements:

  • Gliding: Flat bone surfaces slide over each other.

Special Movements

  • Inversion/Eversion: Movement of the foot's sole inward or outward.

  • Protraction/Retration: Moving a part forward or backward.

  • Elevation and depression: moves a part up or down

Cycle of Life: Articulations

  • Bone development influencing joint stability throughout life :

    • Changes in flexibility and ROM with age.

    • Certain skeletal diseases manifest as joint problems.

The Big Picture: Articulations

  • Mobility of the upper extremity relies on the arrangement of bones, musculature, and their attachments, allowing for object manipulation.