1. 1 Chapter 9: Articulations

2. 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. 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. 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

5. 5

6. 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

7. 7

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

9. 9

10. 10 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

11. 11 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

12. 12

13. 13 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

14. 14

15. 15 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

16. 16

17. 17 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

18. 18 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

19. 19 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

20. 20

21. 21 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

22. 22 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

23. 23

24. 24 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

25. 25 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 REPRESENTATIVE SYNOVIAL JOINTS (cont.)

26. 26

27. 27

28. 28

29. 29 REPRESENTATIVE SYNOVIAL JOINTS (cont.) 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

30. 30

31. 31 REPRESENTATIVE SYNOVIAL JOINTS (cont.) Vertebral joints (Figures 9-13 and 9-14)  Vertebrae are connected to one another by several joints to form a strong flexible column  Bodies of adjacent vertebrae are connected by intervertebral disks and ligaments  Intervertebral disks are composed of two parts Annulus fibrosus: disk’s outer rim, made of fibrous tissue and fibrocartilage Nucleus pulposus: disk’s central core, made of a pulpy, elastic substance

32. 32

33. 33

34. 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. 35

36. 36

37. 37

38. 38

39. 39

40. 40

41. 41 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

42. 42

43. 43 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

44. 44

45. 45 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

46. 46