1. Chapter 9: Articulations

2. INTRODUCTION Articulation: point of contact between bones
Joints are mostly movable, but some are immovable or allow only limited motion
Movable joints allow complex, highly coordinated, purposeful movements to be executed

3. CLASSIFICATION OF JOINTS
Joints may be classified by using a structural or functional scheme (Table 9-1)
Structural classification: joints are named according to:
Presence of a fluid-filled joint capsule (synovial joint)
Type of connective tissue that joins bones together (fibrous or cartilaginous joints)
Functional classification: joints are named according to the degree of movement allowed
Synarthroses: immovable joint
Amphiarthroses: slightly movable
Diarthroses: freely movable

4. CLASSIFICATION OF JOINTS (cont.)
Fibrous joints (synarthroses): bones of joints fit together closely, thereby allowing little or no movement (Figure 9-1)
Syndesmoses: joints in which ligaments connect two bones
Sutures: found only in the skull; teethlike projections from adjacent bones interlock with each other
Gomphoses: between the root of a tooth and the alveolar process of the mandible or maxilla

6. CLASSIFICATION OF JOINTS (cont.)
Cartilaginous joints (amphiarthroses): bones of joints are joined together by hyaline cartilage or fibrocartilage; allow very little motion (Figure 9-2)
Synchondroses: hyaline cartilage present between articulating bones
Symphyses: joints in which a pad or disk of fibrocartilage connects two bones

8. CLASSIFICATION OF JOINTS (cont.)
Synovial joints (diarthroses): freely movable joints (Figure 9-3)
Structures of synovial joints
Joint capsule: sleevelike casing around the ends of the bones
Synovial membrane: membrane that lines the joint capsule and secrete fluid
Articular cartilage: cartilage covering the articular surfaces of bones

9. CLASSIFICATION OF JOINTS (cont.)
Synovial joints (diarthroses): freely movable joints (Figure 9-3)
Structures of synovial joints contd
Joint cavity: small space between the articulating surfaces of the two bones of the joint
Menisci (articular disks): pads of fibrocartilage located between articulating bones
Ligaments: strong cords of dense, white, fibrous tissue that hold the bones of a synovial joint more firmly together
Bursae: synovial membranes filled with synovial fluid; cushion joints and facilitate movement of tendons
Cartilage: firm, whitish, flexible connective tissue found in various forms in the articulating surfaces of join

11. CLASSIFICATION OF JOINTS (cont.)
Synovial joints (cont.)
Types of synovial joints (Figure 9-4)
Uniaxial joints: synovial joints that permit movement around only one axis and in only one plane
Hinge joints: articulating ends of bones form a hinge-shaped unity that allows only flexion and extension
Pivot joints: a projection of one bone articulates with a ring or notch of another bone
Biaxial joints: synovial joints that permit movements around two perpendicular axes in two perpendicular planes
Saddle joints: synovial joints in which the articulating ends of the bones resemble reciprocally shaped miniature saddles; only example in the body is in the thumb
Condyloid (ellipsoidal) joints: synovial joints in which a condyle fits into an elliptical socket

12. CLASSIFICATION OF JOINTS (cont.)
Types of synovial joints (cont.)
Multiaxial joints: synovial joints that permit movements around three or more axes in three or more planes
Ball-and-socket (spheroid) joints: most movable joints; the ball-shaped head of one bone fits into a concave depression
Gliding joints: relatively flat articulating surfaces that allow limited gliding movements along various axes

14. REPRESENTATIVE SYNOVIAL JOINTS
Humeroscapular joint (Figure 9-5)
Shoulder joint
Most mobile joint because of the shallowness of the glenoid cavity
Glenoid labrum: narrow rim of fibrocartilage around the glenoid cavity that lends depth to the glenoid cavity
Structures that strengthen the shoulder joint are ligaments, muscles, tendons, and bursae

16. REPRESENTATIVE SYNOVIAL JOINTS (cont.)
Elbow joint (Figure 9-6)
Humeroradial joint: lateral articulation of the capitulum of the humerus with the head of the radius
Humeroulnar joint: medial articulation of the trochlea of the humerus with the trochlear notch of the ulna
Both components of the elbow joint surrounded by a single joint capsule and stabilized by collateral ligaments
Classic hinge joint
Medial and lateral epicondyles are externally palpable bony landmarks
Olecranon bursa independent of elbow joint space; inflammation called olecranon bursitis
Trauma to nerve results in unpleasant sensations in the fingers and part of the hand supplied by the nerve; severe injury may cause paralysis of hand muscles or reduction in wrist movements

18. REPRESENTATIVE SYNOVIAL JOINTS (cont.)
Proximal radioulnar joint: between the head of the radius and the medial notch of the ulna
Stabilized by the annular ligament
Permits rotation of the forearm
Dislocation of the radial head called a pulled elbow
Distal radioulnar joint: point of articulation between the ulnar notch of the radius and the head of the ulna
Acting with the proximal radioulnar joint permits pronation and supination of the forearm

19. REPRESENTATIVE SYNOVIAL JOINTS (cont.)
Radiocarpal (wrist) joints (Figure 9-7)
Only the radius articulates directly with the carpal bones distally (scaphoid and lunate)
Joints are synovial
Scaphoid bone is fractured frequently
Portion of the fractured scaphoid may become avascular

20. REPRESENTATIVE SYNOVIAL JOINTS (cont.)
Intercarpal joints
Present between eight carpal bones
Stabilized by numerous ligaments
Joint spaces usually communicate
Movements generally gliding with some abduction and flexion

22. REPRESENTATIVE SYNOVIAL JOINTS (cont.)
Carpometacarpal joints: total of three joints
One joint for the thumb—wide range of movements
Two joints for the fingers—movements largely gliding type
Thumb carpometacarpal joint is unique and important functionally
Loose-fitting joint capsule
Saddle-shaped articular surface
Movements: extension, adduction, abduction, circumduction, and opposition
Opposition: ability to touch the tip of the thumb to the tip of other fingers; movement of great functional significance

23. REPRESENTATIVE SYNOVIAL JOINTS (cont.)
Metacarpophalangeal joints (Figure 9-8)
Rounded heads of metacarpals articulate with concave bases of the proximal phalanges
Capsule surrounding joints strengthened by collateral ligaments
Primary movements are flexion and extension

25. REPRESENTATIVE SYNOVIAL JOINTS (cont.)
Interphalangeal joints
Typical diarthrotic, hinge-type, synovial joints
Exist between heads of phalanges and bases of more distal phalanges
Two categories:
Proximal interphalangeal joints: between proximal and middle phalanges
Distal interphalangeal joints: between middle and distal phalanges

26. REPRESENTATIVE SYNOVIAL JOINTS (cont.)
Hip joint (Figure 9-9)
Stable joint because of the shape of the head of the femur and the acetabulum
A joint capsule and ligaments contribute to the joint’s stability
Knee joint (Figures 9-10 and 9-11)
Largest and one of the most complex and most frequently injured joints
Tibiofemoral joint is supported by a joint capsule, cartilage, and numerous ligaments and muscle tendons
Permits flexion, extension and, with the knee flexed, some internal and external rotation

30. REPRESENTATIVE SYNOVIAL JOINTS (cont.)- last one
Ankle joint (Figure 9-12)
Synovial-type hinge joint
Articulation between the lower ends of the tibia and fibula and the upper part of the talus
Joint is mortise, or wedge, shaped
Lateral malleolus lower than medial malleolus
Internal rotation injury results in common “sprained ankle”
Involves anterior talofibular ligament
Other ankle ligaments also may be involved in sprain injuries (e.g., deltoid ligament)
External ankle rotation injuries generally involve bone fractures rather than ligament tears
First-degree ankle injury: lateral malleolus fractured
Second-degree ankle injury: both malleoli fractured
Third-degree ankle injury: fracture of both malleoli and articular surface of tibia

34. TYPES AND RANGE OF MOVEMENT AT SYNOVIAL JOINTS
Measuring range of motion (Figure 9-15)
Range of motion (ROM) assessment used to determine extent of joint injury
ROM can be measured actively or passively; both are generally equal
ROM measured by instrument called a goniometer
Angular movements change the size of the angle between articulating bones
Flexion: decreases the angle between bones; bends or folds one part on another (Figures 9-16, 9-18, and 9-19)
Extension and hyperextension
Extension: increases the angle between bones; returns a part from its flexed position to its anatomical position
Hyperextension: stretching or extending part beyond its anatomical position (Figures 9-19, 9-21, and 9-23)

35. Flexion: decreases the angle between bones; bends or folds one part on another (Figures 9-16, 9-18, and 9-19)
Extension and hyperextension
Extension: increases the angle between bones; returns a part from its flexed position to its anatomical position
Hyperextension: stretching or extending part beyond its anatomical position (Figures 9-19, 9-21, and 9-23)

42. TYPES AND RANGE OF MOVEMENT AT SYNOVIAL JOINTS (cont.)
Plantar flexion and dorsiflexion (Figure 9-25)
Plantar flexion increases the angle between the top of the foot and the front of the leg
Dorsiflexion decreases the angle between the top of the foot and the front of the leg
Abduction and adduction (Figures 9-19 and 9-23)
Abduction moves a part away from the median plane of the body
Adduction moves a part toward the median plane of the body

44. TYPES AND RANGE OF MOVEMENT AT SYNOVIAL JOINTS (cont.)
Circular movements
Rotation and circumduction
Rotation: pivoting a bone on its own axis (Figure 9-16, D)
Circumduction: moves a part so that its distal end moves in a circle
Supination and pronation (Figure 9-20, B)
Supination turns the hand palm side up
Pronation turns the hand palm side down
Gliding movements: simplest of all movements; articular surface of one bone moves over the articular surface of another without any angular or circular movement

46. TYPES AND RANGE OF MOVEMENT AT SYNOVIAL JOINTS (cont.)
Special movements
Inversion and eversion (Figure 9-25, B)
Inversion: turning the sole of the foot inward
Eversion: turning the sole of the foot outward
Protraction and retraction (Figure 9-17, A)
Protraction moves a part forward
Retraction moves a part backward
Elevation and depression (Figure 9-17, B)
Elevation moves a part up
Depression lowers a part

48. CYCLE OF LIFE: ARTICULATIONS
Bone development and the sequence of ossification between birth and skeletal maturity affect joints
Fontanels between cranial bones disappear
Epiphysial plates ossify at maturity
Older adults
ROM decreases
Changes in gait
Skeletal diseases manifest as joint problems
Abnormal bone growth (lipping) influences joint motion
Disease conditions can be associated with specific developmental periods

49. Key points for chapter 9
Hand: “reason for the upper extremity”; thumb: “reason for the hand”
Examples of “big picture” type of thinking when used in functional context
Mobility of the upper extremity is extensive because of the following:
Arrangement of bones in the shoulder girdle, arms, forearm, wrist, and hand
Location and method of attachment of muscles to bones
Proper functioning of joints
Mobility and extensive ROM needed to position upper extremity and hand to permit grasping and manipulation of objects, thus enabling effective interaction with objects in the external environment