Joints & Movement - Comprehensive Notes

Joints (Articulations) & Movement (Chapter 8)

Introduction

Articulations (Joints): site of bone-to-bone connection
Study of Joints: Arthrology
Joint strength decreases as mobility increases
Structure of joints determines:
- Type of movement
- Amount/degree of movement: Range of Motion (ROM)

Classifications:

Structural Classification: based on the anatomical organization of the joint
Functional Classification: based on ROM of the joint.
- Can be further subdivided based on anatomical structure

Structural Classification:

Fibrous:
- Suture: only between skull bones, interlocked by dense regular collagenous C.T. called Sutural Ligament.
- Gomphosis: binds teeth to bony sockets in maxillae and mandible, dense regular collagenous C.T. called Periodontal Ligament
- Syndesmosis: bones connected by a ligament (cord / band or sheet of dense regular collagenous C.T.).
  - Example: anterior tibiofibular ligament between the tibia and fibula (tibiofibular joint)
  - Interosseous Membranes: sheet of dense regular collagenous C.T. that binds neighboring bones.
    - Examples: between tibia & fibula, radius & ulna
Cartilaginous:
- Synchondrosis: a rigid, hyaline cartilage bridge between 2 articulating bones.
  - Examples: epiphyseal plate, between first rib and the sternum (1st sternochondral joint)
- Symphysis: bones separated by a pad of fibrocartilage
  - Examples: pubic symphysis, intervertebral discs, sternal symphyses (manubriosternal & xiphisternal symphyses)
Synovial:
- Hinge
- Ball-and-Socket
- Pivot
- Plane
- Saddle
- Ellipsoid (Condylar)
Bony Fusion/Bony Joint:
- Synostosis: totally rigid & immovable joint – no joint cavity
  - Examples: epiphyseal line, fusion of frontal bones (no sutures seen)

Functional Classification

Synarthrosis: Immovable Joint (no ROM)
- Bony edges are close together, may interlock or fuse.
- Extremely strong joints.
- Located where movement is prevented.
- Bony Fusion/Bony Joint
  - Synostosis (ex: epiphyseal line)
- Fibrous
  - Sutures
- Cartilaginous
  - Synchondrosis (ex: epiphyseal plate)
Amphiarthrosis: Slightly Movable (little ROM)
- Slightly more movement is permitted
- Stronger than freely movable joints
- Fibrous
  - Syndesmosis
  - Gomphosis
- Cartilaginous
  - Symphysis (ex: pubic symphysis)
Diarthrosis: Freely Movable (wide ROM)
- Also called Synovial Joint
- Typically at the ends of long bones
- Subdivided by the nature of movement (planes of movement) nonaxial, monaxial (uniaxial), biaxial, triaxial (multiaxial)

Synovial Joints: Diarthroses

Consist of 4 Distinguishing Features:

Articular Cartilage:
- Articular (hyaline) cartilage covers the ends of the bones forming the joint preventing contact between the bony surfaces
- Slick and smooth
- Not covered by the perichondrium with a more watery matrix
Joint Capsule (Articular Capsule):
- Unique to synovial joints
- Joint surfaces are enclosed by a sleeve or capsule of outer fibrous capsule or fibrous membrane: dense collagenous C.T
  - Continuous with the periostea of the articulating bones
- Lined by a smooth inner synovial membrane: synoviocytes + areolar C.T. & elastic fibers
Joint Cavity (Synovial Cavity):
- Enclosed by the joint capsule
- Contains a thin film of lubricating synovial fluid:
  - Resembles interstitial fluid, but contain high concentration of proteoglycans
  - 3 Primary Functions of Synovial Fluid:
    - Lubrication
    - Nutrient Distribution
    - Shock Absorption
Reinforcing Accessory Structures:
- Pads of cartilage or fat, ligaments, tendons and bursae

Accessory Structures

Tendons:
- Not part of the joint
- Tendons passing across or around a joint stabilizes it (limits the ROM) and provide mechanical support
Cartilages and Fat Pads:
- Several joints contain fat pads:
  - Localized masses of adipose tissue
  - Commonly found superficial to the joint capsule
  - Protect articular cartilages
  - Act as a packing material for the joint
- Some joints (e.g. knee joint) contain meniscus (menisci (pl.)):
  - Pad of fibrocartilage
  - Functions of Meniscus:
    - Shock absorption
    - Improve the fit between the articulating surfaces to make joint more stable
    - Weight distribution over a greater contact surface
Sensory Nerves and Blood Vessels:
- Numerous in synovial joints
- Nerves detect:
  - Sensory receptors: Pacinian Corpuscle (lamellated corpuscle), Ruffini Corpuscle (bulbous corpuscle), free nerve endings
  - Monitors position, movement and stretch of the muscle and joint called proprioceptors:
    - Examples: golgi tendon organ – found in tendons, ligament receptors (golgi-type receptors) – found in some ligaments
Bursae (Bursae (pl.)):
- Small, flattened fluid filled pockets (sac like structures)
- Contain synovial fluid
- Outer dense collagenous C.T. lined with synovial membrane
- May be connected or separate from the joint cavity
- Common where ligaments, muscles, skin, tendons, and bones rub together
Tendon Sheaths (Synovial Sheaths):
- Elongated bursa that wraps completely around a tendon
- Protects all sides of tendon as they slide back & forth
Ligaments:
- Support, strengthen, reinforce articulating bones
Bursitis: inflammation of bursa (synovial membrane)
- Due to excessive local friction, infection, arthritis, or direct trauma
Sprain: ligament is stretched to the point where some or all the collagen fibers are torn (varies in severity)

Injuries to Synovial Joints:

Luxation: Complete Dislocation
- Articulating bones are forced out of position
- Damages articular cartilage, ligaments, joint capsule
Subluxation: Partial Dislocation

Types of Articular Movements or Motion

Gliding (Linear) Movement:
- Articulating bone or bones move linearly, slipping pass each other
- Examples: between carpal bones (intercarpal joints), between tarsal bones (intertarsal joints), between clavicle and sternum (claviculosternal joint)
Angular Movement:
- Articulating bone can change angle that pivots at the point of articulation
- Includes circumduction
- Flexion:
  - Angle decreases between articulating bones
- Extension:
  - Angle increases between articulating bones
  - Anatomical position: all the major joints of the axial and appendicular skeleton are at full extension (except for ankle joint)
- Hyperextension:
  - Extension past the anatomical position (not possible for many joints due to ligaments, bony processes or soft tissue)
- Circumduction:
  - Special type of angular movement
  - Moving arm in a loop (hand moves in a circle, but arm does not rotate)
- Abduction:
  - Movement away from the midline of the body in frontal or coronal plane
- Adduction:
  - Moving towards midline in frontal or coronal plane (back to anatomical position)
Rotation Movement:
- Partial rotation, not a complete $360^o$
- Articulating bone can spin at the point of articulation around its longitudinal axis
- Rotation of the Head:
  - Left or Right rotation
- Rotation of the Limb:
  - Medial rotation (inward rotation) – Rotates toward axis
  - Lateral rotation (outward rotation) – Rotates away from axis
- Rotation of the Forearm:
  - Pronation
    - Palm facing posteriorly
  - Supination
    - Palm facing anteriorly (anatomical position)
Special Movements: applies to specific articulation or unusual types of movement
- Lateral Excursion
  - Mandible moves to the right or left
- Medial Excursion
  - Mandible returns to the midline
- Elevation
  - Movement in superior direction (up)
- Depression
  - Movement in inferior direction (down)
- Opposition
  - Thumb movement toward fingers or palm (grasping)
- Reposition
  - Thumb brought back to anatomical position
- Protraction
  - Moves anteriorly in the horizontal plane (pushes forward)
- Retraction
  - Moves posteriorly - opposite of protraction (pulls back)
- Inversion
  - Twists sole of foot medially
- Eversion
  - Twists sole of foot laterally
- Dorsiflexion
  - Flexion at ankle (lifting toes)
- Plantar flexion
  - Extension at ankle (pointing toes)

Planes (Axes) of Dynamic Motion or Movement

Nonaxial (Translational)
- Gliding allows only small amounts of movement: back-and-forth, and side-to-side
- Gliding does not permit rotation or angular movements
- Plane (Gliding) Joints (intercarpal joints of the wrists, intertarsal joints, and claviculosternal joints)
Monaxial (Uniaxial)
- Movement along one axis: angular or rotation movement
- Hinge Joints (elbow joint), Pivot Joints (proximal radio-ulnar joint)
Biaxial
- Movement along two axes: angular, but not rotational movement
- Condylar Joints (radiocarpal joint, metacarpophalangeal joints 2-5), Saddle Joints (carpometacarpal joint of thumb)
Triaxial (Multiaxial)
- Movement along three axes: angular and rotational movement
- Ball-and-socket Joints (shoulder and hip joints)

Types of Synovial Joints: Based on the shapes of the articulating surfaces

Gliding Joint (Plane Joint):
- Flattened or slightly curved articulating surfaces that slide across one another back-and-forth, side-to-side (although very slight)
- Nonaxial (Translational)
Hinge Joint:
- Angular movement in one axis (monaxial)
- Monaxial (Uniaxial)
Pivot Joint:
- Rotational movement in one axis (monaxial)
- Monaxial (Uniaxial)
Ellipsoid Joint (Condylar Joint):
- Oval articular face within a depression allowing for angular movements around two axes (including circumduction), but not rotation
- Biaxial
Saddle Joint:
- Concave-convex articulation permitting angular movement around two axes (including limited circumduction), but not rotation
- Biaxial
Ball-and-Socket Joint:
- Round head of one bone within a cup-shaped depression in another
- All combinations of angular (including circumduction) and rotational movements
- Triaxial (Multiaxial)

Specific Synovial Joints:

Shoulder Joint (Glenohumeral Joint):

A ball-and-socket joint
Allows more motion than any other joint
The least stable joint
Supported by skeletal muscles, tendons, ligaments
Processes of the Shoulder Joint
- Acromion (clavicle) and Coracoid Process (scapula)
  - Project laterally, superior to the humerus
  - Help stabilize the joint
Socket of the Shoulder Joint
- Glenoid labrum
  - Deepens socket of glenoid cavity
  - Fibrocartilage lining
  - Extends past the bone - between head of humerus and glenoid cavity of scapula
Shoulder Ligaments
- Glenohumeral
- Coracohumeral
- Coracoacromial
- Coracoclavicular
- Acromioclavicular
Shoulder Muscles (Rotator Cuff)
- Supraspinatus
- Infraspinatus
- Subscapularis
- Teres minor

Elbow Joint (Cubital Joint):

Humeroulnar Joint
- Largest joint
- Between the humerus and ulna
- A stable hinge joint due to thick joint capsule, bony surfaces of humerus and ulna that interlock closely
- Contain multiple strong ligaments to reinforce the elbow joint
Humeroradial Joint
- Smaller joint
- Between the humerus and radius
Proximal Radioulnar Joint
- Between the proximal radius and ulna
With articulations involving humerus, radius, and ulna
Strong Ligaments:
- Radial collateral ligament
  - Stabilizes joint at lateral surface
  - Extends around head of radius
- Ulnar collateral ligament
  - Stabilizes medial side of the joint
  - Extends from medial epicondyle of humerus to coronoid and olecranon of ulna
- Radial annular ligament
  - Surrounds the neck of the radius
  - Binds head of the radius to the ulna

Hip Joint (Coxal Joint):

Head of femur fits into the socket of acetabulum (extended by fibrocartilaginous acetabular labrum)
Strong ball-and-socket joint: diarthrosis
Wide range of motion
Ligaments of the Hip Joint
- Iliofemoral
- Pubofemoral
- Ischiofemoral
- Transverse acetabular
- Ligamentum teres

Knee Joint

A complicated hinge joint
Transfers weight from femur to tibia
Articulations of the knee joint
- Two femur–tibia articulations: at medial and lateral condyles of the femur and tibia
- One between patella and patellar surface of femur
Seven Major Supporting Ligaments
- Patellar Ligament (anterior)
- (2) Popliteal Ligaments (posterior)
- Anterior Cruciate Ligament (ACL)
- Posterior Cruciate Ligaments (PCL)
- Tibial Collateral Ligament (Medial Collateral Ligament: MCL)
- Fibular Collateral Ligament (Lateral Collateral Ligament: LCL)
Medial and Lateral Menisci
- Pads of fibrocartilage
- Located at femur–tibia articulations
- Shock absorption
- Improves the fit between the articulating surfaces of the femur and tibia
- Provides lateral and medial support to the knee
- Helps distributes the upper body weight across their surfaces

Degenerative Changes to Joints:

Rheumatism:

A general term that indicates pain and stiffness
Affects the skeletal system, muscular system or both

Arthritis

Encompasses all the rheumatic diseases that affect synovial joints
Always involves damage to the articular cartilages due varying causes
Types of Arthritis:
1. Osteoarthritis: OA (Degenerative Arthritis or Degenerative Joint Disease (DJD):
  - Generally affects people 60 or older
  - Most common form of arthritis
  - A chronic degenerative condition
  - Course is usually slow and irreversible
  - Joints most affected: fingers, cervical and lumbar joints, knees and hips
  - Can result from:
    - Cumulative wear and tear at the joint surfaces
    - Genetic factors (family history of OA)
    - Joint injury that occurred in earlier years
    - Obesity (chronic extra weight placed on the joint)
  - In US: 25% of women and 15% of men over age 60 are affected
2. Rheumatoid Arthritis: RA
  - An inflammatory disorder
  - Affects about 0.5-1.0% of adult population (affects 3 times as many women as men)
  - Usually occurs between ages 40-50, but may occur at any age
  - An autoimmune disease (may be the result of bacterial or viral infections)
  - Marked by remissions and flareups
  - Often occurs symmetrically
  - All cases involve restricted joint movement and extreme pain
3. Gouty Arthritis (Gout):
  - Accumulation of uric acid crystals (needle-like crystals) within the synovial joint
  - Metabolism of purines produces uric acid
  - Symptoms include intense pain and inflammation that typically affects a single joint (often the big toe)
  - Other joints that can also be affected such as the ankles, knees, wrists, fingers, and elbows.
  - More common in men than women with onset typically after 30
  - Strong genetic component
  - Most people with gout will experience repeated bouts over the years.