Chapter 8

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1

Joints or Articulations & FUNCTION:

- sites where 2 or more bones meet

Functions:
- Give skeleton mobility
- Hold skeleton together

Classified by
- Structure (material) and
- Function (type of movement)

2

STRUCTURE:

- material binding bones together and
- presence/absence of joint cavity

3

Fibrous joints:

(bones held together by dense fibrous connective tissue)

4

Cartilaginous joints:

(bones held together by cartilage)

5

Synovial joints:

(have synovial cavity, space between
bones, articular capsule, ligaments): MOST joints of the body

6

Functional classification:

(=amount of movement joint allows)

7

Synarthrosis:

immovable joints (syn=together):
****ex sutures of the skull and other axial skeleton

8

Amphiarthrosis:

slightly movable joint (amphi= both sides)
***Ex: intervertebral disks and other axial skeleton

9

Diarthrosis:

freely movable joint (diarthro=movable): all are synovial
****joints of appendicular skeleton

10

Fibrous Joints:

Lack a synovial cavity

The articulating bones are held very closely together by dense fibrous connective tissue

Fibrous joints permit little or no movement

11

Sutures:

(sutur=seam):
- only between skull bones
fibrous connective tissue ossify and fuse in adult

12

Syndesmoses:

(syndesmo=ligament)

Tibio-fibular ligament, Interosseus membrane (tibia-fibula)

13

Gomphoses:

(a peg or nail fitting into a socket)

Roots of the teeth in the socket

14

Cartilaginous Joints:

- Articulating bones are joined by cartilage (hyaline or fibrocartilage)
- Lacks a synovial cavity
- Allows little or no movement

15

Two types of cartilaginous joints:

1. Synchondroses
2. Symphyse

16

Synchondroses:

(syn=together, chondro=cartilage):
hyaline cartilage

- epiphyseal plate of long bones (children)
- first rib + manubrium joint

17

Symphyse:

(growing together):
fibrocartilage

- pubis symphisis
- intervertebral joint

18

Synovial Joints:

- Articulating bones are separated by a fluid-containing joint cavity, the “Synovial cavity”
- Most joints, all joints of limbs
- Allow a joint to be freely movable. All diarthroses

19

Articular cartilage:

- hyaline cartilage covering the articulating bones:
- slippery, reduces friction

20

Synovial Cavity:

space containing synovial fluid

21

Articular Capsule:

- encloses the synovial cavity
- composed of "two layers"
- outer tough fibrous membrane
- inner "synovial membrane" secreting synovial fluid

22

Synovial Fluid:

- Viscous slippery filtrate of plasma + hyaluronic acid
- Lubricates (reduces friction) and nourishes articular cartilage (avascular)

23

Reinforcing Ligaments:

hold bones together in a synovial joint
- Extracapsular and intracapsular
- Muscles also important in reinforcing some joints (shoulder, knee)

24

Articular Discs (knee: Menisci, sing: meniscus):

- Pads of fibro-cartilage lie between the articular surfaces of the bones
- Meniscectomy (arthroscopy surgery for torn cartilage)
- "Improve the fit" between articulating bone ends making the joint more stable

25

Rich Nerve and Blood Supply:

- Nerve fibers detect pain, monitor joint position and stretch
- Capillary beds produce filtrate for synovial fluid

26

Sprain:

wrenching/twisting of a joint with resulting overstretching of "ligament/s"

27

Strain:

stretched or partially torn "muscle or tendon"

28

“Bags of Lubricant”:

reduce friction

29

Bursae:

(purse)
- Flat sac-like structures containing synovial fluid
- Located where tendons, ligaments muscles, skin or bones, rub together (ex: knee, shoulder)
- Cushion, reduce friction

30

Tendon sheaths:

"Elongated bursae" that "wrap around some tendons" subject to friction

31

Nonaxial:

slipping movement only

32

Uniaxial (or monoaxial):

Movement around one plane
***Ex. Bending lower limb at knee and
straightening

33

Biaxial :

Movement around two perpendicular planes
***Ex bending hand at wrist and then side to side

34

Triaxial :

- Movement around all three planes
- Arm at shoulder joint

35

Gliding /Planar:

- Simple movement back-and-forth and from side-to-side of flat or slightly curved bones

- One flat bone surface glides or slips over another similar surface

- Limited in range

- Intercarpal, intertarsal joints

- Between articular processes
of vertebrae

36

Angular Movements:

Increase or a decrease in the angle between articulating bones

Angular movements include
Flexion
Extension
Lateral flexion
Hyperextension
Abduction
Adduction
Circumduction

37

Flexion (bend):

Decrease in the angle between articulating bones

***Ex: bending the head towards the chest

38

Extension (stretch):

- Increase in the angle between articulating bones often after a flexion to restore anatomical position

- Flexion and extension are "opposite" movements

39

Hyperextension:

- Continuation of extension "beyond the normal extension"

- Bending the head/trunk backward, moving the humerus/femur back while walking

40

Lateral flexion:

Movement of the trunk sideways to the right or left at the waist

41

Abduction:

(ab=away, duct=lead)

- Movement of a bone "away from the midline"

- Moving the humerus laterally at the shoulder joint

42

Addauction:

- Movement of a bone "toward the midline"

- Movement that returns body parts to normal position from abduction

43

Hands/feet:

midline is along the longest/middle finger

44

Circumduction:

- Movement of the distal end of the body part in a "circle"

- Circumduction —flexion + abduction + extension + adduction of a limb so as to describe a cone in space

- Moving the humerus in a circle at the shoulder joint, moving the hand in a circle

45

Rotation:

- A bone revolves around its own longitudinal axis

- Turning the head from side to side as when you shake your head “no” (between C1 and C2 vertebrae)

46

Special Movements:

Elevation
Depression
Protraction
Retraction
Inversion
Eversion
Dorsiflexion
Plantar flexion
Supination
Pronation
Opposition

47

Inversion:

Movement of the foot medially
Its opposing movement is eversion

48

Eversion:

Movement of the sole laterally

49

Dorsiflexion:

- Bending of the foot in an upward direction

- Opposing movement is plantar flexion

50

Plantar flexion:

Bending of the foot in a downward direction

51

Supination:

- Movement of the forearm so that the palm is turned upward
- Its opposing movement is pronation

52

Pronation:

Movement of the forearm so that the palm is turned downward

53

Opposition:

Movement of the thumb: thumb moves to touch the tips of the fingers on the same hand

54

Synovial joints are classified based on the:

SHAPE of the articular surfaces

55

Planar / Gliding Joints:

- Primarily permit back-and-forth and side-to-side movements

- Intercarpal / intertarsal joints, joints between articular processes of vertebrae

56

Hinge Joints:

- permits flexion and extension

- Produce an opening and closing motion like that
of a hinged door (convex+concave)

**Knee and elbow

57

Pivot Joints:

- permit rotation

- Surface of one pointed or rounded bone articulates with a ring formed partly by another bone

- Joints that enable the palms to turn anteriorly and posteriorly

- Atlanto-axial joint, proximal radio-ulnar joint

58

Condyloid Joints (or ellipsoidal joint):

permit angular motion Both articular surfaces are "OVAL"

***Hand

59

Saddle Joints:

Articular surface of one bone is saddle-shaped, and the articular surface of the other bone fits into the “saddle”

***Thumb

60

Ball-and-Socket Joints:

- the most movable, all angular movement

- Ball-like surface of one bone fitting into a cuplike depression of another bone

- Shoulder (humerus and glenoid cavity scapula) and
hip (femur and hip bone acetabulum

61

Range of motion (ROM):

Range, measured in degrees of a circle, through which the bones of a joint can be moved

62

Articulating bones:

Shape of bones determines how closely they fit together

63

Ligaments/Muscles:

- strength and tension

- Ligaments are tense when the joint is in certain positions

- Tense ligaments restrict the range of motion

64

Hormones:

- Flexibility may also be affected by hormones (Relaxin from placenta, ovaries, increases the flexibility of the pubic symphysis and loosens the ligaments between the sacrum and hip bone toward the end of pregnancy

65

Disuse:

- Movement restricted if a joint has not been used

- (vv) synovial fluid, (vv) flexibility ligaments and tendons, muscular atrophy

66

Knee Joint :

- Largest and most complex joint of the body

- Modified hinge joint: consists of 3 joints within a single synovial cavity
1. Femoro-Patella joint: plane joint, allows gliding
2. and 3. Tibio-femoral joints: (lateral and medial): between femoral condyle and tibia menisci): allows flexion, extension, slight rotation

67

Menisci (medial and lateral):

- articular fibrocartilage disks, increase fit of articulating bones and help prevent side-to-side rocking of the femur on the tibia

68

Knee: Ligaments :

- Capsule is not complete (absent anteriorly),
reinforced by broad tendons

- Anteriorly, the quadriceps tendon gives
rise to 3 broad ligaments:

- Lateral and medial patellar retinacula
- Patellar ligament (knee-jerk reflex “tapping”)

69

Main ligaments that secure the bones and prevent hyperextension and joint displacement:

1. Intracapsular:
- cruciate ligaments (ant + post. cross each other), prevent anterior-posterior displacement

2. Extracapsular:
- reside outside the capsule:
- Popliteal ligaments (oblique, arcuate)
- Fibular and tibial collateral

70

Shoulder Joint (gleno-humeral joint):

- Ball & Socket joint: formed by head of humerus and glenoid cavity of scapula

- More freedom of movement than any other joint of the body (shallow glenoid cavity), but less stability

- Allows: flexion, extension, hyperextension,
abduction, adduction, rotation, circumduction of the arm

71

Ligaments:

- Coracohumeral ligament—helps support the weight of the upper limb

- Three glenohumeral ligaments—somewhat weak anterior reinforcements

72

Muscle tendons:

Tendon of the long head of biceps: secures humerus to glenoid cavity

73

Four rotator cuff tendons encircle the shoulder joint:

Subscapularis
Supraspinatus
Infraspinatus
Teres minor

74

Elbow Joint:

- Hinge joint formed by the humerus (trochlea, capitulum) with the ulna, and the radius

- Prominent structure: humerus trochlea with trochlear notch of Ulna

- Allows only flexion and extension of the forearm

75

Hip Joint:

- Ball & Socket joint formed by the femur head and
the hip bone acetabulum

- Strongest articular capsule and ligaments

- Allows: flexion, extension, abduction,
adduction, rotation, circumduction

- Good range of motion, limited by deep socket

76

Reinforcing ligaments:

Iliofemoral ligament
Pubofemoral ligament
Ischiofemoral ligament
Ligamentum teres

77

Temporo-mandibular joint :

- Combined hinge and planar joint formed by the mandible (condyles) and the temporal bone

- Only movable joint between skull bones: only the mandible moves

- Allows: depression, elevation (=hinge), lat excursion, protraction, retraction (gliding/planar)

***Most easily dislocated joint in the body

78

Cartilage tears (ex knee meniscus tear):

- Due to compression and shear stress

- Fragments may cause joint to lock or bind

- Cartilage rarely repairs itself

-Repaired with arthroscopic surgery: meniscectomy
(removal of the meniscus)

79

Dislocations (luxations):

- Bones forced out of alignment

- Accompanied by sprains, inflammation, and difficulty moving joint

- Caused by serious falls or contact sports

- Must be reduced to treat

80

Subluxation:

partial dislocation of a joint

81

Bursitis:

- An inflammation of a bursa, usually caused by a blow or friction

- Treated with rest and ice and, if severe, anti-inflammatory drugs

82

Tendonitis:

- Inflammation of tendon sheaths typically caused by overuse (ie carpal tunnel)

- Symptoms and treatment similar to bursitis

83

Arthritis:

Osteoarthritis
Rheumatoid Arthritis (RA)
Gouty Arthritis
Lyme Disease

84

Osteoarthritis (OA):

- Most common of arthritis and joint
disorder

- Irreversible, degenerative (“wear-and-tear”)

- Degradation of joints, including articular cartilage

- Treatment: moderate activity, mild pain relievers, capsaicin creams, glucosamine and chondroitin sulfate, joint replacement surgery

85

Rheumatoid Arthritis (RA):

- Chronic, autoimmune disease of unknown cause:
the immune system attacks its own tissue(cartilageand joint linings)

- Inflammation of the joint (symmetrical), which causes swelling, pain and loss of function:
- Inflammatory blood cells migrate to the joint and release cytokines

- Inflamed synovial membrane thickens and cartilage is eroded and fibrous tissue is deposited in joint and calcifies (“pannus”) making the joint "immovable"

***
Treatment:
Aspirin, long-term use of antibiotics, physical therapy
Anti-inflammatory drugs, immunosuppressants
New biological response modifier drugs neutralize
inflammatory chemicals

86

Gouty Arthritis:

- Build up of "uric acid" in the blood (uric
acid derives from metabolism of nucleic acids
followed by deposition of uric acid crystals in soft tissues of the joints: causing cartilage erosion and "inflammation"

- More common in men

- Typically affects the joint at the base of the great toe

***
Treatment: anti-inflammatory drugs, allopurinol (keeps uric acid low), plenty of water, avoidance of alcohol

87

Lyme Disease:

- Caused by bacteria transmitted by the bites of ticks
- the Borrelia Burgorferi bacteria, from Lyme, CT, transmitted by tear ticks (tiny)

- A rash may appear (bull’s eye), joint stiffness, fever, chills, headache, stiff neck, later arthritis at the larger joints

****Treatment: early antibiotics. If untreated > neurological disorders, irregular heart beat

88

Aging:

- May result in decreased production of synovial fluid

- The articular cartilage becomes thinner

- Ligaments shorten and lose some of their flexibility

- Very subtle degenerative changes may begin at age 20; age 80 most people have some, especially at vertebral column (hunched-over posture)

89

Arthroplasty:

- Joints may be replaced surgically with artificial joints

- Most commonly replaced are the hips, knees, and shoulders

90

Hip Replacements:

- Partial hip replacements involve "only the femur"

- Total hip replacements involve both the "acetabulum" and "head of the femur"

- Prosthesis: artificial devices: acetabulum: plastic polyethylene, femur: metal cobalt/chrome, titanium, stainless steel

91

Knee Replacements:

- Actually a resurfacing of cartilage

- May be partial or total

- Potential complications of arthroplasty include infection, blood clots, loosening or dislocation of the replacement components, and nerve injury

- May activate metal detector at security check