1. Joints 8

2. Joints (Articulations)
Weakest parts of the skeleton
Articulation – site where two or more bones meet
Functions of joints
Give the skeleton mobility
Hold the skeleton together

3. Classification of Joints: Structural
Structural classification focuses on the material binding bones together and whether or not a joint cavity is present
The three structural classifications are:
Fibrous
Cartilaginous
Synovial

4. Fibrous Structural Joints
The bones are joined by fibrous tissues
There is no joint cavity
Most are immovable
There are three types – sutures, syndesmoses, and gomphoses

5. Fibrous Structural Joints: Sutures
Occur between the bones of the skull
Comprised of interlocking junctions completely filled with connective tissue fibers
Bind bones tightly together, but allow for growth during youth

6. Fibrous Structural Joints: Sutures
Figure 8.1a

7. Fibrous Structural Joints: Syndesmoses
Bones are connected by a fibrous tissue ligament
Movement varies from immovable to slightly variable
Examples include the connection between the tibia and fibula, and the radius and ulna

8. Fibrous Structural Joints: Syndesmoses
Figure 8.1b

9. Fibrous Structural Joints: Gomphoses
The peg-in-socket fibrous joint between a tooth and its alveolar socket
The fibrous connection is the periodontal ligament

10. Articulating bones are united by cartilage Lack a joint cavity
Cartilaginous Joints
Articulating bones are united by cartilage
Lack a joint cavity
Two types – synchondroses and symphyses

11. Cartilaginous Joints: Synchondroses
A bar or plate of hyaline cartilage unites the bones
All synchondroses are synarthrotic
Examples include:
Epiphyseal plates of children
Joint between the costal cartilage of the first rib and the sternum

12. Cartilaginous Joints: Synchondroses
Figure 8.2a, b

13. Cartilaginous Joints: Symphyses
Hyaline cartilage covers the articulating surface of the bone and is fused to an intervening pad of fibrocartilage
Amphiarthrotic joints designed for strength and flexibility
Examples include intervertebral joints and the pubic symphysis of the pelvis

14. Cartilaginous Joints: Symphyses
Figure 8.2c

15. All are freely movable diarthroses
Synovial Joints
Those joints in which the articulating bones are separated by a fluid-containing joint cavity
All are freely movable diarthroses
Examples – all limb joints, and most joints of the body

16. Synovial Joints: General Structure
Synovial joints all have the following
Articular cartilage
Joint (synovial) cavity
Articular capsule
Synovial fluid
Reinforcing ligaments

17. Synovial Joints: General Structure
Figure 8.3a, b

18. Synovial Joints: Friction-Reducing Structures
Bursae – flattened, fibrous sacs lined with synovial membranes and containing synovial fluid
Common where ligaments, muscles, skin, tendons, or bones rub together
Tendon sheath – elongated bursa that wraps completely around a tendon

19. Synovial Joints: Movement
The two muscle attachments across a joint are:
Origin – attachment to the immovable bone
Insertion – attachment to the movable bone
Described as movement along transverse, frontal, or sagittal planes

20. Synovial Joints: Range of Motion
Nonaxial – slipping movements only
Uniaxial – movement in one plane
Biaxial – movement in two planes
Multiaxial – movement in or around all three planes

21. Types of Synovial Joints
Plane joints
Articular surfaces are essentially flat
Allow only slipping or gliding movements
Only examples of nonaxial joints
Figure 8.7a

22. Types of Synovial Joints
Hinge joints
Cylindrical projections of one bone fits into a trough-shaped surface on another
Motion is along a single plane
Uniaxial joints permit flexion and extension only
Examples: elbow and interphalangeal joints

23. Types of Synovial Joints
Figure 8.7b

24. Only uniaxial movement allowed
Pivot Joints
Rounded end of one bone protrudes into a “sleeve,” or ring, composed of bone (and possibly ligaments) of another
Only uniaxial movement allowed
Examples: joint between the axis and the dens, and the proximal radioulnar joint

25. Pivot Joints
Figure 8.7c

26. Condyloid, or Ellipsoidal, Joints
Oval articular surface of one bone fits into a complementary depression in another
Both articular surfaces are oval
Biaxial joints permit all angular motions
Examples: radiocarpal (wrist) joints, and metacarpophalangeal (knuckle) joints

27. Condyloid, or Ellipsoidal, Joints
Figure 8.7d

28. Similar to condyloid joints but allow greater movement
Saddle Joints
Similar to condyloid joints but allow greater movement
Each articular surface has both a concave and a convex surface
Example: carpometacarpal joint of the thumb

29. Saddle Joints
Figure 8.7e

30. Ball-and-Socket Joints
A spherical or hemispherical head of one bone articulates with a cuplike socket of another
Multiaxial joints permit the most freely moving synovial joints
Examples: shoulder and hip joints

31. Ball-and-Socket Joints
Figure 8.7f

32. One flat bone surface glides or slips over another similar surface
Gliding Movements
One flat bone surface glides or slips over another similar surface
Examples – intercarpal and intertarsal joints, and between the flat articular processes of the vertebrae

33. Flexion — bending movement that decreases the angle of the joint
Angular Movement
Flexion — bending movement that decreases the angle of the joint
Extension — reverse of flexion; joint angle is increased
Dorsiflexion and plantar flexion — up and down movement of the foot
Abduction — movement away from the midline
Adduction — movement toward the midline
Circumduction — movement describes a cone in space

34. Gliding Movement
Figure 8.5a

35. Angular Movement
Figure 8.5b

36. Angular Movement
Figure 8.5c, d

37. Angular Movement
Figure 8.5e, f

38. The turning of a bone around its own long axis
Rotation
The turning of a bone around its own long axis
Examples
Between first two vertebrae
Hip and shoulder joints
Figure 8.5g

39. Supination and pronation Inversion and eversion
Special Movements
Supination and pronation
Inversion and eversion
Protraction and retraction
Elevation and depression

40. Special Movements
Figure 8.6a

41. Special Movements
Figure 8.6b

42. Special Movements
Figure 8.6c

43. Special Movements
Figure 8.6d