Chapter 9 Articulations

1. Chapter 9Articulations

2. Introduction • Articulation • Point of contact between bones • Joints are mostly very movable, but others are immovable or allow only limited motion • Movable joints allow complex, highly coordinated, and purposeful movements to be executed

3. Classification of Joints • Joints may be classified using a structural or functional scheme (Table 9-1) • Structural classification • Joints are named according to one of the following: • Type of connective tissue that joins bones together • Fibrous • Cartilaginous • Presence of a fluid-filled joint capsule • Synovial joint

4. Classification of Joints • Joints may be classified (cont.) • Functional classification • Joints are named according to degree of movement allowed: • Synarthroses—immovable joint • Amphiarthroses—slightly movable • Diarthroses—freely movable

5. Classification of Joints • Fibrous joints • Synarthroses • Bones of joints fit together closely • Allow little or no movement (Figure 9-1) • Syndesmoses - joints in which ligaments connect two bones • Sutures - found only in skull; toothlike projections from adjacent bones interlock with each other • Gomphoses - between root of a tooth and the alveolar process of the mandible or maxilla

6. Fibrous Joints

7. Classification of Joints • 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. Cartilaginous Joints

9. Classification of Joints • Synovial joints (diarthroses) • Freely movable joints (Figure 9-3) • Structures of synovial joints • Joint capsule - sleevelike casing around ends of bones, binding them together • Synovial membrane - lines joint capsule and also secretes synovial fluid • Articular cartilage - hyaline cartilage covering articular surfaces of bones

10. Classification of Joints • Structures of synovial joints (cont.) • 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 bones of synovial joint more firmly together • Bursae -synovial membranes filled with synovial fluid; cushion joints and facilitate movement of tendons

12. Classification of Joints • 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 • Projection of one bone articulates with a ring or notch of another bone

13. Classification of Joints • Types of synovial joints (cont.) • 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 occurrence in body is in thumbs • Condyloid (ellipsoidal) joints - synovial joints in which a condyle fits into an elliptical socket

14. Classification of Joints • 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; 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

16. 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 glenoid cavity that lends depth to the cavity • Structures that strengthen the shoulder joint are ligaments, muscles, tendons, and bursae

21. Representative Synovial Joints • Hip joint (Figure 9-6) • Stable joint because of shape of head of femur and of acetabulum • A joint capsule and ligaments contribute to joint’s stability

26. Representative Synovial Joints • Knee joint (Figures 9-10 and 9-11) • Largest and one of most complex and most frequently injured joints • Tibiofemoral joint is supported by a joint capsule, cartilage, and numerous ligaments and muscle tendons • Permits flexion and extension and, with knee flexed, some internal and external rotation

28. Representative Synovial Joints • Vertebral joints (Figures 9-10 and 9-11) • 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 made up 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

31. Representative Synovial Joints • Elbow joint • Humeroradial joint—lateral articulation of capitulum of humerus with head of radius • Humeroulnar joint—medial articulation of trochlea of humerus with trochlear notch of ulna • Both components of elbow joint surrounded by single joint capsule and stabilized by collateral ligaments

32. Representative Synovial Joints • Elbow joint (cont.) • 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 those fingers and part of hand supplied by nerve; severe injury may cause “wrist drop”

33. Representative Synovial Joints • Proximal radioulnar joint—between head of radius and medial notch of ulna • Stabilized by annular ligament • Permits rotation of forearm • Dislocation of radial head called “pulled elbow” • Distal radioulnar joint—point of articulation between ulnar notch of radius and head of ulna • Together with proximal radioulnar joint, permits pronation and supination of forearm

34. Representative Synovial Joints • Radiocarpal (wrist) joints • Only radius articulates directly with carpal bones distally (scaphoid and lunate) • Joints are synovial • Scaphoid bone is fractured frequently • Portion of fractured scaphoid may become avascular

35. Representative Synovial Joints • Intercarpal joints • Between 8 carpal bones • Stabilized by numerous ligaments • Joint spaces usually communicate • Movements generally gliding, with some abduction and flexion

36. Representative Synovial Joints • Carpometacarpal joints—total of three joints • One joint for thumb—wide range of movements • Two joints for 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 tip of thumb to tip of other fingers—movement of great functional significance

37. Representative Synovial Joints • Metacarpophalangeal joints • Rounded heads of metacarpals articulate with concave bases of proximal phalanges • Capsule surrounding joints strengthened by collateral ligaments • Primary movements are flexion and extension

38. Representative Synovial Joints • Interphalangeal joints • Typical diarthrotic, hinge-type, synovial joints • Occur between heads of phalanges and bases of more distal phalanges • Two categories: • PIP joints—proximal interphalangeal joints (between proximal and middle phalanges) • DIP joints—distal interphalangeal joints (between middle and distal phalanges)

39. Representative Synovial Joints • Ankle joint (Figure 9-12) • Hinge type of synovial joint • Articulation between lower ends of tibia and fibula and upper part of talus • Joint is “mortise” or wedge-shaped • Lateral malleolus lower than medial

40. Representative Synovial Joints • Ankle joint (cont.) • Internal rotation injury results in common “sprained ankle” • Involves anterior talofibular ligament • Other ankle ligaments may also be involved in sprain injuries—example is deltoid ligament

41. Representative Synovial Joints • Ankle joint (cont.) • 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

43. Types and Range of Movement at Synovial Joints • Measuring range of motion (Figure 9-12) • Range of motion (ROM) assessment used to determine extent of joint injury • ROM can be measured actively or passively; results of both methods generally about equal • ROM measured by instrument called a goniometer

44. Types and Range of Movement at Synovial Joints • Angular movements - change the size of the angle between articulating bones • Flexion • Decreases the angle between bones; bends or folds one part on another • 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 \

45. Types and Range of Movement at Synovial Joints • Angular movements (cont.) • Plantar flexion and dorsiflexion • Plantar flexion - increases angle between top of foot and front of leg • Dorsiflexion - decreases angle between top of foot and front of leg • Abduction and adduction • Abduction - moves a part away from median plane of body • Adduction - moves a part toward median plane of body

46. Types and Range of Movement at Synovial Joints • Circular movements • Rotation and circumduction • Rotation - pivoting a bone on its own axis • Circumduction - moves a part so that its distal end moves in a circle • Supination and pronation (Figure 9-19, B) • Supination - turns the hand palm side–up • Pronation - turns the hand palm side–down

47. Types and Range of Movement at Synovial Joints • Gliding movements • Simplest of all movements • Articular surface of one bone moves over articular surface of another without any angular or circular movement

48. Types and Range of Movement at Synovial Joints • Special movements • Inversion and eversion • Inversion - turning sole of foot inward • Eversion - turning sole of foot outward • Protraction and retraction (Figure 9-16, B) • Protraction - moves a part forward • Retraction - moves a part backward • Elevation and depression • Elevation - moves a part up • Depression - lowers a part

49. 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 occur • Skeletal diseases manifest as joint problems • Abnormal bone growth (lipping)—influences joint motion • Disease conditions can be associated with specific developmental periods

50. The Big Picture: Articulations • Hand—“reason for the upper extremity” and thumb—“reason for the hand” • Examples of “Big Picture” type of thinking when used in functional context