Topic 4_Anatomy and Physiology of Joints

Anatomy & Physiology of Joints

• Types of Joints: Classified by structure and mobility.

  • Fibrous Joints: Little to no movement (e.g., sutures in the skull).

  • Cartilaginous Joints: Limited movement (e.g., pubic symphysis).

  • Synovial Joints: Full range of movement, most common in limbs.

Objectives of the Study

• Understand classification of joints:

  • Fibrous Joints: Describe structure and give examples.

  • Cartilaginous Joints: Outline general structure and types.

  • Synovial Joints: Discuss structure, stability factors, movement types, and major body joints.

Classification of Joints

• Structural Classification:

  • Fibrous Joints: Two bones connected by dense connective tissue.

  • Cartilaginous Joints: Bones unified by cartilage.

  • Synovial Joints: Joint cavity present, allowing for significant movement.

• Functional Classification:

  • Synarthroses: Immovable joints (e.g., sutures).

  • Amphiarthroses: Slightly movable joints (e.g., intervertebral discs).

  • Diarthroses: Freely movable (e.g., shoulder, elbow).

Fibrous Joints

• Types:

  • Synostoses (sutures): Immovable joints, only found in the skull.

  • Syndesmoses: Joints connected by ligaments; movement varies based on fiber length.

  • Gomphoses: Peg-in-socket (e.g., tooth in its socket).

• Characteristics:

  • Connected by dense connective tissue.

  • No joint cavity present.

  • Movement is typically minimal or non-existent.

Cartilaginous Joints

• Types:

  • Synchondroses: Bones connected by bar or plate of hyaline cartilage; mostly immovable (e.g., epiphyseal plates).

  

  • Symphyses: Bones connected by a plate of fibrocartilage; provide strength with flexibility (e.g., pubic symphysis).

  • Ends covered with hyaline, plate of fibrocartilage between

  

• Characteristics:

  • No joint cavity.

  • Limited movement.

Synovial Joints Structure

• Features:

  1. Articular Cartilage: Covers bone surfaces, cushions joints.

  2. Joint Cavity: Small fluid-filled space reduces friction.

  3. Articular Capsule: Two layers (outer fibrous layer and inner synovial membrane).

  4. Synovial Fluid: Lubricates joints.

  5. Reinforcing Ligaments: Add stability, can be capsular, extracapsular, or intracapsular.

  

  6. Nerve and Blood Supply: Detects pain and monitors joint position.

Bursae and Tendon Sheaths

• burase: bags of synovial fluid that act as a lubricating “ball bearing”

• tendon sheath: elongated form that wraps around tendons

2. Ligaments

   • more lig. = more strength

   • ligaments can only stretch ~6% before break

3. Muscle tone

   • tendons of muscles crossing joints usually MOST IMPORTANTin stabilizing the joint, as they help maintain the position, keep taut by muscle tone

     • esp. shoulderknee, arches of foot

Stability:

-allow lots of movement, not as stable as fibrous cartilage/joint

1. Articular surfaces

   1. Shape of articular surfaces of many joints are such that they dont contribute stability

      • deep ball and socket joints have good shape for mobility

Movement Types of Synovial Joints

• Movement Categories:

  • Nonaxial: Gliding only.

    • e.g.

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

  • Biaxial: Movement in two planes (e.g., condyloid joints knuckle).

  • Multiaxial: Movement in all three planes (e.g., ball-and-socket joints shoulder and hip).

• General Movements:

  • Gliding Movements: Flat surfaces slide past each other.

  • Angular Movements: Increase or decrease the angle between two bones.

  • Rotation: Bone turns around its own axis.

Examples of Specific Movements

• Flexion and Extension: Alter angle between bones in sagittal plane.

• Abduction and Adduction:

  • Abduct: away from midline

  • Adduct: towards midline

• Circumduction: Circular movement at joints.

• Special Movements:

  • Pronation and Supination: Rotational movements of the forearm.

    • drink soup

  • Dorsiflexion and Plantarflexion: Foot movement towards or away from shin.

  • Opposition: Movement of thumb to touch fingers.

• Movements of the Mandible: Protraction, retraction, elevation, and depression.

• Feet

  • Dorsiflexion: Movement that brings the toes closer to the shin, allowing for activities such as walking on heels.

  • Plantar flexion: Movement that points the toes away from the shin, facilitating actions like standing on tiptoes or pushing off during running.

  • Inversion: turn the sole of the foot medially

  • Eversion turn the sole of the foot laterally

• Jaw (mandible)

  • Elevation: up (close mouth)

  • Depression: down (open mouth)

  • Protraction: stick out jaw anteriorly

  • Retraction: pull jaw back posteriorly

Types of Synovial Joints

• Based on Shape:

  • Plane (gliding movement).

    • two flat opposing surfaces

  • Hinge (flexion and extension).

    • cylinder into trough

    • flexion extension (elbow)

    • uniaxial

  • Pivot (rotation)

    • insertion into a ring or sleeve

    • between atlas and dens of axis; proximal radio ulnar joint

  • Condyloid (movement in all planes).

    • “knuckle joint'“

    • articulating surfaace like an oval

    • All planes of motion

  • Saddle (enhanced movement).

    • surface on one bone is saddle, other bone fits into

    • most freely moving

  • Ball-and-socket (most freely moving).

    • multiaxial joints

    • freely moving

    • e.g. shoulder/hips.

Specific Joint Examples

• Shoulder Joint: Ball-and-socket; stabilized by rotator cuff tendons.

  • glenoid cavity broadened slightly by the glenoid labrum

  • largely the tendons of the rotator cuff muscles that stabilize this joint

• Elbow Joint: Hinge; primary movements are flexion and extension; stabilized by collateral ligaments.

  • humerus articulates with radius and ulna

  • annular ligament allows rotation of the radius during pronation and supination

  • ulnar collateral

  • radial collateral

• Hip Joint: Deep ball-and-socket; includes intracapsular and extracapsular ligaments.

  • deep ball and socket

  • intracapsular ligament that extends from the fovea capitis to ligamentum teres

  • extracapsular ligaments: iliofemoral, pubofemoral and ischiofemoral

  • the articular surface does provide some stability

    

• Knee Joint: Hinge; complex structure with multiple ligaments for stabilization.

  

  • largest and most complex

  • doesnt allow movementin multiple planes, primarily permitting flexion and extension.

    • when flex knee allows slight rotation

  • described as having 3 individual joints

  

  Temporomandibular Joint (TMJ): Modified hinge; allows for opening/closing and side-to-side jaw movement.

  • has articular disc

    • serves to divide joint capsule into superior and inferior parts

    • initial jaw opening is hingeded, while further opening involves a gliding motion facilitated by the articular disc, allowing for a full range of motion during activities such as chewing and speaking.

Summary of Midterm Evaluation

• Content for Midterm 1 includes information discussed in lectures and slides; not responsible for extraneous details from the textbooks.