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9 Articulations
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An Introduction to Articulations
Learning Outcomes 9-1 Contrast the major categories of joints, and explain the relationship between structure and function for each category. 9-2 Describe the basic structure of a synovial joint, and describe common synovial joint accessory structures and their functions. 9-3 Describe how the anatomical and functional properties of synovial joints permit movements of the skeleton. 9-4 Describe the articulations between the vertebrae of the vertebral column.
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An Introduction to Articulations
Learning Outcomes 9-5 Describe the structure and function of the shoulder joint and the elbow joint. 9-6 Describe the structure and function of the hip joint and the knee joint. 9-7 Describe the effects of aging on articulations, and discuss the most common age-related clinical problems for articulations. 9-8 Explain the functional relationships between the skeletal system and other body systems.
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An Introduction to Articulations
Body movement occurs at joints (articulations) where two bones connect Joint Structure Determines direction and distance of movement (range of motion or ROM) Joint strength decreases as mobility increases
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9-1 Classification of Joints
Two Methods of Classification Functional classification is based on range of motion of the joint Structural classification relies on the anatomical organization of the joint
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9-1 Classification of Joints
Functional Classifications Synarthrosis (immovable joint) Amphiarthrosis (slightly movable joint) Diarthrosis (freely movable joint)
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9-1 Classification of Joints
Structural Classifications Bony Fibrous Cartilaginous Synovial
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Table 9-1 Functional and Structural Classifications of Articulations
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Table 9-1 Functional and Structural Classifications of Articulations
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Table 9-1 Functional and Structural Classifications of Articulations
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9-1 Classification of Joints
Synarthroses (Immovable Joints) Are very strong Edges of bones may touch or interlock Four types of synarthrotic joints Suture Gomphosis Synchondrosis Synostosis
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9-1 Classification of Joints
Suture Bones interlocked Are bound by dense fibrous connective tissue Are found only in skull Gomphosis Fibrous connection (periodontal ligament) Binds teeth to sockets
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9-1 Classification of Joints
Synchondrosis Is a rigid cartilaginous bridge between two bones Epiphyseal cartilage of long bones Between vertebrosternal ribs and sternum Synostosis Fused bones, immovable Metopic suture of skull Epiphyseal lines of long bones
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9-1 Classification of Joints
Amphiarthroses More movable than synarthrosis Stronger than freely movable joint Two types of amphiarthroses Syndesmosis Bones connected by ligaments Symphysis Bones separated by fibrocartilage
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9-1 Classification of Joints
Synovial Joints (Diarthroses) Also called movable joints At ends of long bones Within articular capsules Lined with synovial membrane
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9-2 Synovial Joints Articular Cartilages
Pad articulating surfaces within articular capsules Prevent bones from touching Smooth surfaces lubricated by synovial fluid Reduce friction
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9-2 Synovial Joints Synovial Fluid
Contains slippery proteoglycans secreted by fibroblasts Functions of synovial fluid Lubrication Nutrient distribution Shock absorption
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9-2 Synovial Joints Accessory Structures Cartilages Fat pads Ligaments
Tendons Bursae
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9-2 Synovial Joints Cartilages Fat Pads Ligaments Cushion the joint
Fibrocartilage pad called a meniscus (or articular disc; plural, menisci) Fat Pads Superficial to the joint capsule Protect articular cartilages Ligaments Support, strengthen joints Sprain – ligaments with torn collagen fibers
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9-2 Synovial Joints Tendons Bursae Attach to muscles around joint
Help support joint Bursae Singular, bursa, a pouch Pockets of synovial fluid Cushion areas where tendons or ligaments rub
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9-2 Synovial Joints Factors That Stabilize Synovial Joints
Prevent injury by limiting range of motion Collagen fibers (joint capsule, ligaments) Articulating surfaces and menisci Other bones, muscles, or fat pads Tendons of articulating bones
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Figure 9-1a The Structure of a Synovial Joint
Medullary cavity Spongy bone Periosteum Fibrous joint capsule Synovial membrane Articular cartilages Joint cavity (containing synovial fluid) Compact bone Synovial joint, sagittal section 22
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Figure 9-1b The Structure of a Synovial Joint
Quadriceps tendon Bursa Joint capsule Femur Patella Synovial membrane Articular cartilage Meniscus Fat pad Patellar ligament Intracapsular ligament Joint cavity Tibia Meniscus Knee joint, sagittal section 23
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9-2 Synovial Joints Injuries Dislocation (luxation) Subluxation
Articulating surfaces forced out of position Damages articular cartilage, ligaments, joint capsule Subluxation A partial dislocation
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9-3 Movements Three Types of Dynamic Motion
Linear movement (gliding) Angular movement Rotation Planes (Axes) of Dynamic Motion Monaxial (1 axis) Biaxial (2 axes) Triaxial (3 axes)
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Figure 9-2 A Simple Model of Articular Movement
Initial position Gliding movement Angular movement Circumduction Rotation 26
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Figure 9-2a A Simple Model of Articular Movement
Initial position Initial position of the model. The pencil is at right angles to surface. 27
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Figure 9-2b A Simple Model of Articular Movement
Gliding movement Possible movement 1, showing gliding, an example of linear movement. The pencil remains vertical, but tip moves away from point of origin. 28
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Figure 9-2c A Simple Model of Articular Movement
Angular movement Possible movement 2, showing angular movement. The pencil tip remains stationary, but shaft changes angle relative to the surface. 29
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Figure 9-2d A Simple Model of Articular Movement
Circumduction Possible movement 2, showing a special type of angular movement called circumduction. Pencil tip remains stationary while the shaft, held at an angle less than 90º, moves in a conical pattern to complete a circle. 30
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Figure 9-2e A Simple Model of Articular Movement
Rotation Possible movement 3, showing rotation. With tip at same point, the angle of the shaft remains unchanged as the shaft spins around its longitudinal axis. 31
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9-3 Movements Types of Movement at Synovial Joints Terms describe:
Plane or direction of motion Relationship between structures
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9-3 Movements Types of Movement at Synovial Joints Gliding Movement
Two surfaces slide past each other Between carpal or tarsal bones
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9-3 Movements Angular Movement Flexion Extension Angular motion
Anterior–posterior plane Reduces angle between elements Extension Increases angle between elements
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Figure 9-3a Angular Movements
Extension Flexion Hyperextension Flexion Flexion Hyper- extension Extension Extension Flexion Hyperextension Extension Flexion/extension 35
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9-3 Movements Angular Movement Hyperextension Angular motion
Extension past anatomical position
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Figure 9-3a Angular Movements
Extension Flexion Hyperextension Flexion Flexion Hyper- extension Extension Extension Flexion Hyperextension Extension Flexion/extension 37
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9-3 Movements Angular Movement Abduction Adduction Angular motion
Frontal plane Moves away from longitudinal axis Adduction Moves toward longitudinal axis
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Figure 9-3b Angular Movements
Abduction Abduction Adduction Adduction Abduction Adduction Abduction Adduction Abduction/adduction 39
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Figure 9-3c Angular Movements
Adduction Abduction Adduction/abduction 40
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9-3 Movements Angular Movement Circumduction
Circular motion without rotation Angular motion
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Figure 9-3d Angular Movements
Circumduction 42
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9-3 Movements Types of Movement at Synovial Joints Rotation
Direction of rotation from anatomical position Relative to longitudinal axis of body Left or right rotation Medial rotation (inward rotation) Rotates toward axis Lateral rotation (outward rotation) Rotates away from axis
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Figure 9-4a Rotational Movements
Head rotation Right rotation Left rotation Lateral (external) rotation Medial (internal) rotation 44
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9-3 Movements Types of Movements at Synovial Joints Rotation Pronation
Rotates forearm, radius over ulna Supination Forearm in anatomical position
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Figure 9-4b Rotational Movements
Supination Pronation Supination Pronation 46
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9-3 Movements Special Movements Inversion Eversion Dorsiflexion
Twists sole of foot medially Eversion Twists sole of foot laterally Dorsiflexion Flexion at ankle (lifting toes) Plantar flexion Extension at ankle (pointing toes)
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Figure 9-5 Synovial Joints
Eversion Inversion 48
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Figure 9-5 Synovial Joints
Dorsiflexion (ankle flexion) Plantar flexion (ankle extension) 49
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9-3 Movements Special Movements Opposition
Thumb movement toward fingers or palm (grasping) Reposition Opposite of opposition Protraction Moves anteriorly In the horizontal plane (pushing forward) Retraction Opposite of protraction Moving anteriorly (pulling back)
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Figure 9-5 Synovial Joints
Opposition 51
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Figure 9-5 Synovial Joints
Retraction Protraction 52
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9-3 Movements Special Movements Elevation Depression Lateral flexion
Moves in superior direction (up) Depression Moves in inferior direction (down) Lateral flexion Bends vertebral column from side to side
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Figure 9-5 Synovial Joints
Depression Elevation 54
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Figure 9-5 Synovial Joints
Lateral flexion 55
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9-3 Movements Classification of Synovial Joints by Shape Gliding Hinge
Pivot Condylar Saddle Ball-and-socket
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9-3 Movements Gliding Joints Hinge Joints Pivot Joints
Flattened or slightly curved faces Limited motion (nonaxial) Hinge Joints Angular motion in a single plane (monaxial) Pivot Joints Rotation only (monaxial)
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Figure 9-6 Synovial Joints
Gliding joint Movement: slight nonaxial or multiaxial Clavicle Examples: • Acromioclavicular and claviculosternal joints Manubrium • Intercarpal and intertarsal joints • Vertebrocostal joints • Sacro-iliac joints 58
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Figure 9-6 Synovial Joints
Hinge joint Movement: monaxial Examples: Humerus • Elbow joint • Knee joint • Ankle joint Ulna • Interphalangeal joint 59
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Figure 9-6 Synovial Joints
Pivot joint Movement: monaxial (rotation) Examples: Atlas • Atlanto-axial joint • Proximal radio-ulnar joint Axis 60
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9-3 Movements Condylar Joints Saddle Joints Ball-and-socket Joints
Oval articular face within a depression Motion in two planes (biaxial) Saddle Joints Two concave, straddled (biaxial) Ball-and-socket Joints Round articular face in a depression (triaxial)
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Figure 9-6 Synovial Joints
Condylar joint Movement: biaxial Examples: • Radiocarpal joint Scaphoid bone • Metacarpophalangeal joints 2–5 • Metatarsophalangeal joints Ulna 62
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Figure 9-6 Synovial Joints
Saddle joint Movement: biaxial Examples: • First carpometacarpal joint III II Metacarpal bone of thumb Trapezium 63
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Figure 9-6 Synovial Joints
Ball-and-socket joint Movement: triaxial Examples: Scapula • Shoulder joint • Hip joint Humerus 64
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9-3 Movements Joints A joint cannot be both mobile and strong
The greater the mobility, the weaker the joint Mobile joints are supported by muscles and ligaments, not bone-to-bone connections ANIMATION Representative Articulations: A Functional Classification of Synovial Joints
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9-6 The Knee Joint The 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 One between patella and patellar surface of femur
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9-6 The Knee Joint The Articular Capsule and Joint Cavity
Medial and lateral menisci Fibrocartilage pads At femur–tibia articulations Cushion and stabilize joint Give lateral support
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9-6 The Knee Joint Seven Major Supporting Ligaments
Patellar ligament (anterior) 2. & 3. Two popliteal ligaments (posterior) 4. & 5. Anterior and posterior cruciate ligaments (inside joint capsule) Tibial collateral ligament (medial) Fibular collateral ligament (lateral)
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Figure 9-12a The Right Knee Joint
Quadriceps tendon Patella Joint capsule Patellar retinaculae Tibial collateral ligament Fibular collateral ligament Patellar ligament Tibia Anterior view, superficial layer 69
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Figure 9-12b The Right Knee Joint
Femur Joint capsule Plantaris muscle Gastrocnemius muscle, medial head Gastrocnemius muscle, lateral head Bursa Fibular collateral ligament Tibial collateral ligament Cut tendon of biceps femoris muscle Popliteal ligaments Popliteus muscle Tibia Fibula Posterior view, superficial layer 70
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Figure 9-12c The Right Knee Joint
Patellar surface Fibular collateral ligament Posterior cruciate ligament Lateral condyle Medial condyle Tibial collateral ligament Lateral meniscus Cut tendon Medial meniscus Anterior cruciate ligament Tibia Fibula Deep anterior view, flexed 71
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Figure 9-12d The Right Knee Joint
Femur Posterior cruciate ligament Fibular collateral ligament Medial condyle Lateral condyle Tibial collateral ligament Lateral meniscus Medial meniscus Cut tendon Anterior cruciate ligament Fibula Tibia Deep posterior view, extended 72
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9-7 Effects of Aging on Articulations
Degenerative Changes Rheumatism A pain and stiffness of skeletal and muscular systems Arthritis All forms of rheumatism that damage articular cartilages of synovial joints Osteoarthritis Caused by wear and tear of joint surfaces, or genetic factors affecting collagen formation Generally in people over age 60
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9-7 Effects of Aging on Articulations
Rheumatoid Arthritis An inflammatory condition Caused by infection, allergy, or autoimmune disease Involves the immune system Gouty Arthritis Occurs when crystals (uric acid or calcium salts) Form within synovial fluid Due to metabolic disorders
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9-7 Effects of Aging on Articulations
Joint Immobilization Reduces flow of synovial fluid Can cause arthritis symptoms Treated by continuous passive motion or CPM (therapy) Bones and Aging Bone mass decreases Bones weaken Increases risk of hip fracture, hip dislocation, or pelvic fracture
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9-8 Integration with Other Systems
Bone Recycling Living bones maintain equilibrium between: Bone building (osteoblasts) And breakdown (osteoclasts)
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9-8 Integration with Other Systems
Factors Affecting Bone Strength Age Physical stress Hormone levels Calcium and phosphorus uptake and excretion Genetic and environmental factors
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9-8 Integration with Other Systems
Bones Support Body Systems Support and protect other systems Store fat, calcium, and phosphorus Manufacture cells for immune system
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9-8 Integration with Other Systems
Bones Support Body Systems Disorders in other body systems can cause: Bone tumors Osteoporosis Arthritis Rickets (vitamin D deficiency)
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