1. Joints of the Skeletal System
Chapter 8
Joints of the Skeletal System

2. Classification of Joints

3. Joints of the Skeletal System
Articulations
Functional junctions between bones
Bind parts of skeletal system together
Make bone growth possible
Permit parts of the skeleton to change shape during childbirth
Enable body to move in response to skeletal muscle contraction

4. Functional Classification Of Joints
Classification=based on the amount of movement allowed
3 types:
Synarthroses = immovable joints
Example = sutures of skull
Amphiarthroses = slightly movable joints.
Example = intervertebral discs between vertebrae
Diarthroses = freely movable joints
Examples = joints of appendicular skeleton

5. Structural Classification Of Joints
Classification= Based on material, which joins bones
3 types:
Fibrous
Cartilaginous
Synovial

6. Fibrous Joints joints composed of fibrous tissue
no joint cavity is present
3 types:
Syndesmosis
Suture
Gomphosis

7. Fibrous Joints cont.
Syndesmosis = cord of fibrous tissue called a ligament
amphiarthroses with "give" but no true movement
Example = distal tibiofibular joint

8. Fibrous Joints cont. Sutures = short fibrous CT fibers synarthroses
Only found in skull

9. Fibrous Joints cont.
Gomphosis = tooth within its bony socket (alveolar fossa)
short periodontal ligament

10. Cartilaginous Joints joints composed of cartilage no joint cavity
2 types:
Synchondrosis
Symphysis

11. Cartilaginous Joints cont.
Synchondrosis = a plate of hyaline cartilage
sites of bone growth during youth
eventually ossify = synarthrotic
Examples: joint between the first rib and manubrium and the epiphyseal plate

12. Cartilaginous Joints cont.
Symphysis = pad or plate of fibrocartilage
compressible "shock absorber"
limited movement = amphiarthroses
Examples: intervertebral discs and symphysis pubis

13. Synovial Joints = fluid-filled joint cavity
free movement = diarthrosis

14. General Structure Of A Synovial Joint
General Structure Of A Synovial Joint = 5 distinct features:
1. Articular cartilage = hyaline cartilage covers the surface of each bone
2. Joint cavity = a potential space between the two bones, filled with synovial fluid
3. Synovial fluid = viscous lubricating fluid within cavity
reduces friction between cartilages of 2 bones
provide lubrication
nourish cartilage
contain phagocytes

15. Synovial Joints cont.
4. Articular capsule = double layered capsule surrounding cavity:
External, tough flexible fibrous capsule (continuous with periosteum of the bones)
Synovial membrane = loose CT lining of fibrous capsule, that also covers all internal joint surfaces excluding hyaline cartilage
5. Reinforcing ligaments = ligaments that strengthen joint
Definition: A ligament joins a bone to another bone across a synovial joint
usually thickened portions of fibrous capsule (intrinsic or capsular)

16. General Structure of a Synovial Joint

17. Synovial Joints cont. Other joint features: fatty pads (hip & knee)
menisci or articular discs or that separate cavity into 2 compartments (knee, jaw, sternoclavicular)

18. Synovial Joints cont.
bursa = flattened fibrous sacs with a synovial membrane and fluid that act as "ball bearings" to prevent friction on adjacent structures during joint activity
cushion the movement of one body part over another;
located between skin and bone (where skin rubs over bone), and between muscle, tendons, ligaments and bone.

19. Types Of Synovial Joints
Ball-and-socket joints = most freely movable joints; all angular movement
The head of one bone fits into the socket of another
Examples = hip and shoulder
Condyloid joints = permit all angular motion, except rotation
Examples = wrists and knuckles

20. Types Of Synovial Joints cont.
Gliding joints = cartilaginous joints
Example = intervertebral discs
Hinge joints = permit flexion & extension only
Examples = elbow and knee

21. Types Of Synovial Joints cont.
Pivot joints = permit rotation
Example = first intervertebral joint (atlantoaxial joint)
Saddle joints = thumb

22. Types Of Joint Movements

23. Introduction Origin = part of muscle attached to the immovable bone
Insertion = part of a muscle attached to the movable bone
When a muscle contracts across a joint, its insertion is pulled toward its origin

24. Three general types of movement
Gliding movements = when flat bone surfaces glide or slide over one another
occur at cartilaginous joints
Examples = intervertebral discs and sternoclavicular joints
Angular movements = changes in angles between bones
occur only at synovial joints

26. Movement cont. Flexion = decreasing the angle between 2 bones.
Example = head toward chest
Dorsiflexion = bringing foot closer to shin
Plantar flexion = pointing one's toe (flexion toward the sole)
Extension = increasing the angle between 2 bones
Example = straightening a flexed neck
Hyperextension = increasing the angle greater than 180o

28. Movement cont. Abduction = moving a limb away from the midline.
Example = raising arm or thigh laterally;
Adduction = moving a limb toward the midline

30. Movement cont.
Circumduction = moving a limb in a circular (cone-shaped) manner
Rotation = turning movement of a bone along its long axis.
Example = atlas over axis (i.e. “just say no”)
Example = shoulder and hip joint

32. Special Movements Special Movements = those at specific joints
supination/pronation = movements between the radius and ulna at the proximal radioulnar joint
thumb up = supination
thumb down = pronation
inversion/eversion = movement of foot
sole inward = inversion
sole out = eversion

34. Special Movements cont.
elevation/depression
shoulder shrug = elevation
mandible in opening mouth = depression
protraction/retraction
thrust forward = protraction
pull back = retraction

36. Shoulder joint Shoulder joint (2 joints)
Ball and socket is the glenohumeral joint
joins Glenoid cavity and head of humerus
Syndesmosis is called the acromioclavicular joint
acromial end of clavicle and the acromion process of the scapula
Ball and socket is surrounded by many reinforcing ligaments and tendons collectively called the rotator cuff
Many bursa also lubricate the shoulder
Movement can occur in any angular plane

38. Elbow joint
(2 joints)
Hinge is between trochlea of humerus and trochlear notch of ulna
Gliding joint is between capitulum of humerus and head of radius
Very stable joint with many reinforcing ligaments
Only allows flexion and extension

40. Hip joint (coxal joint)
Ball and socket between head of femur and acetabulum of coxa
Contains many large reinforcing ligaments
Allows same movements as shoulder, but with less range due to bony limitations

42. Knee (3 joints) Largest, most complex joint
Functions as a hinge even though 3 joints work together
Medial condyles of femur and tibia make one condyloid joint
Lateral condyles of femur and tibia make another condyloid joint
Patellar surface of femur and patella make a gliding joint
Flexion and extension with some slight rotation
Contains many reinforcing structures

43. Knee cont. Menisci C-shaped fibrocartilage pads medial meniscus
lateral meniscus
C-shaped fibrocartilage pads
Reshape the tibial condyles for a better fit
Absorb shock
Many bursae