1. JOINTS
Chapter 9

2. Introduction
Joints or articulations are sites where two or more bones meet
Joints have two fundamental functions:
provide for skeletal mobility
hold the skeleton together
Weakest parts of the skeleton, yet have a remarkable ability to resist the forces that tear them apart

3. Classification of Joints
Structural classification
focuses on the material binding the bones together and whether or not there is a joint cavity (fibrous, cartilaginous, synovial)
Functional classification
based on the amount of movement allowed at the joint (synarthroses, amphiarthoroses, diarthroses)

4. Functional Classification
Synarthroses
Immovable joints
Amphiarthroses
Slightly movable joints
Diarthroses
Freely movable joints

5. Structural Classification
Fibrous
Joined by fibrous tissue
Cartilaginous
Joined by cartilage
Synovial
The bones are joined and surrounded by a joint cavity
Note:
Structural classification is the system used in your text

6. Summary of Joint Classes
Fibrous joints
Suture
Syndesmoses
Gomphoses
Cartilaginous joints
Synchondroses
Symphyses
Synovial
Gliding, hinge, pivot, condyloid, saddle, and ball and socket

7. Fibrous Joints
In fibrous joints the bones are joined by fibrous tissue; no joint is present. The three types of fibrous joints are. . .
Sutures
Dense fibrous connective tissue
Syndesmosis
A cord or band of connective tissue
Gomphosis
Peg-in-socket arrangement surrounded by fibrous tissue or peridontal ligament

8. Suture Joint Occurs only between bones of the skull
Wavy articulating bone edges interlock
Junction is filled by connective tissue
Rigid splices bind bones of the skull together tightly

9. Syndesmosis Longer fibrous tissue occurs as a sheet or membrane
Longer fibrous tissue permits the joint to “give” or flex
True movement is not possible

10. Gomphosis Fibrous tissue holds teeth in their sockets
Teeth embedded in sockets of bone
Anchored by fibers of periodontal ligament

11. Cartilaginous Joints
In cartilaginous joints, the articulating bones are united by cartilage, there is no joint cavity
Synchondroses
Hyaline cartilage unites the bones
Symphyses
Fibrocartilage unites the bones

12. Synchondroses Hyaline cartilage unites the bones
Epiphyseal plates in growing children
Provide for bone growth
When growth ends all synchondroses become immovable
Epipyseal
Plate

13. Synchrondroses
Sternocostal joint between the manubrium and rib 1 is a immovable hyaline cartilage joint

14. Symphyses
Bone surfaces are covered with articular hyaline cartilage which is fused to a pad of fibrocartilage
Fibrocartilage is resilient and acts as a shock absorber and permits limited movement

15. Synovial Joints
In synovial joints articulating bones are located within a fluid containing joint cavity
Synovial joints permit substantial range of motion
All synovial joints have similar features

16. Structures of Synovial Joint
Articular cartilage
Hyaline cartilage on opposing bone surfaces
Joint (synovial) cavity
Space filled with fluid
Articular capsule
Capsule to confine fluid
Synovial fluid
Fluid to lubricate joints
Reinforcing ligaments
Maintain joint alignment

17. Articular Cartilage Hyaline cartilage covers the bone surfaces
Cartilage absorbs the compression placed on the joint
Cartilage keeps the bone ends from being crushed

18. Joint (synovial) cavity
Joint spaces are unique to synovial joints
Joint spaces are filled with synovial fluid

19. Articular capsule
The joint cavity is enclosed by a double layered articular capsule
The external layer is a tough flexible fibrous capsule
The inner synovial membrane

20. Synovial Fluid Synovial fluid fills the entire joint
Slippery fluid lubricates joint
Weeping lubrication squeezes synovial fluid into and out of the cartilage nourishing the cells
Synovial
Fluid

21. Reinforcing ligaments
Extracapsular
Ligament
Ligaments reinforce joints
Intrinsic ligaments reinforce capsule
Extracapsular are outside capsule
Intracapsular are inside capsule
Intracapsular
Ligament

22. Features of Select Synovial Joints
Certain synovial joints have additional structural features
Fatty pads cushion the knee and hip joints
Fibrocartilage articular discs separates articular surfaces (menisci)
Articular discs improve the fit between the articulating surfaces (knee, jaw)

23. Bursae and Tendon Sheaths
Bursae and tendon sheaths are closely associated with synovial joints
Essentially sacs of lubricant
Function as “ball bearings” to reduce friction between adjacent structures
Reduces friction during joint activity

24. Bursae
Bursae are flattened fibrous sacs lined with synovial membrane and containing a thin film of synovial fluid
Common at sites where ligaments, skin, muscles or tendons rub against a bone

25. Bursae: Anomolies
A bunion is an enlarged bursae at the base of the big toe
False bursae may develop at any site where there is excessive motion
Function similar to a true bursae

26. Tendon Sheaths
An elongated bursa that wraps completely around a tendon subjected to friction
Tendon slides within this lubricated sleeve
Common at sites where the tendon is subject to friction from other tendons or bone features
Tendon
Sheath

27. Retinaculum
Retinaculum
Retinaculum function to confine tendons to a specific line of pull
Muscle exerts a force around a skeletal feature
Similar to a pulley or gear changing the angle of force exerted by a machine

28. Factors Influencing Synovial Joint Stability
The stability of a synovial joint depends on three factors . . .
The nature of the articular surfaces
The number and positioning of the ligaments
The tone and strength of the muscles acting upon the joint

29. Articular Surfaces
The surfaces determine what movements are possible at a joint, but play a minimal role in joint stability
Many joints have shallow, “misfit” surfaces
Larger surfaces or deeper sockets vastly improve stability
Ball and socket joints are very stable because of their articular surfaces

30. Articular Surfaces The knee is a hinge joint by classification
The knee is an example of a joint that allows for “extra” movements
The joint surfaces allow for some anterior - posterior sliding, sliding, as well as a slight amount of rotation at full extension

31. Ligaments Ligaments unite the bones of a joint
Ligaments help to direct bone movement and prevent excessive or undesirable motion
As a rule, the more ligaments a joint has the stronger it is
Ligaments can stretch due to undue tension or trauma
Ligaments can stretch only 6% of its length before it snaps

32. Supporting Ligaments
The supporting ligaments of the elbow allow flexion / extension and restrict movement in any other plane
The Annular ligament allows for rotation of the head of the radius but restricts other movements

33. Muscle Tone
In most joints the muscles that act upon a joint are the most important stabilizing factor
The tendons of the muscles keep the joint taunt and provide dynamic support
Muscle tone is extremely important in reinforcing the shoulder and knee joint as well as the arches of the foot
The articular capsule and the ligament have extensive sensory nerve endings providing reflexive contraction of supporting muscles

34. Muscle Tone The knee is a joint that features movement over stability
The knee is very dependent upon the muscles to provide dynamic stability to the joint while it moves
Note: Rehab

35. Movements Allowed by Synovial Joints
Nonaxial
Biaxial
Multiaxial

36. Gliding Movements Simplest type of joint movement
Bone surface glides or slips over another similar surface
Occur at the intercarpal and intertarsal joints as well as articular processes of vertebrae

37. Flexion/Extension Flexion Extension
A bending movement that decreases the angle of the joint
Extension
A movement that increases the angle of the joint

38. Flexion/Extension/Hyperextension
A bending movement that decreases the angle of the joint
Extension
A movement that increases the angle of the joint
Hyperextension
Bending beyond the upright position

39. Flexion Flexion Illustrated
A bending movement that decreases the angle of the joint and brings the two articulating bones closer together
Movement usually occurs in the sagittal plane
Illustrated
Flexion of the arm
Flexion of the leg

40. Extension Extension Illustrated
A movement that increases the angle of the joint that moves the two articulating bones farther apart
Movement within the sagittal plane
Illustrated
Extension of the leg and arm

41. Dorsiflexion and Plantar Flexion
Lifting the foot so that its superior surface nears the shin
Plantar flexion
Depressing the foot or pointing the toes downward

42. Ab/Adduction/Circumduction
Abduction
Movement of a limb away from midline or a spreading of the digits of the hand or foot
Adduction
Movement of a limb toward midline or in the case of the digits toward the midline of the hand or foot
Circumduction
Movement of a limb in a circle

43. Rotation Rotation is the turning of a bone around its own long axis
Only movement possible between C1 & C2
Common at the hip and shoulder joints
Medial or lateral is a function of whether rotation results in the anterior surface of the limb moving toward or away from the midline of the body

44. Supination and Pronation

45. Inversion and Eversion

46. Protraction and Retraction

47. Elevation and Depression

48. Opposition

49. Types of Synovial Joints
Although all synovial joints have the same features they do not have a common structural plan
Based on the shape of their articular surfaces there are six major categories of synovial joints
Plane, hinge, pivot, condyloid, saddle, and ball and socket

50. Plane Joint A plane joint is the only example of a nonaxial joint
Articular surfaces are essentially flat
Allow only short slipping or gliding movements

51. Plane Joints No rotation around an axis Examples Plane joints
Intercarpals
Intertarsals
Vertebrae
Plane
joints

52. Hinge Joints
In hinge joints a cylindrical shaped projection of bone fits into a trough shaped surface of another bone
Motion is within a single plane
Joint components resemble that of a mechanical hinge

53. Hinge Joints The elbow joint is an example of a hinge joint
It allows for movement (flexion and extension) in only one plane
Other example
Knee

54. Pivot Joints
The rounded end of a bone protrudes into a ring of bone and ligaments on another bone
Only movement allowed is rotation of bone around long axis

55. Pivot Joints
An example is the joint between the atlas and axis, which allows your head to move side to side
Another example is the proximal radioulnar joint, where the head of the radius rotates within the annular ligment

56. Condyloid Joints
In condyloid joints the oval articular surface of one bone fits into a comple- mentary concavity in another
Both articulating surfaces are oval shaped

57. Condyloid Joints The biaxial joints permits all angular motions
flexion / extension
abduction adduction
Circumduction
Metacarpo- phalangeal joints

58. Saddle Joints
Resemble condyloid joints, but allow greater freedom of movement
Each surface has both a concave and a convex surface that fit together
Each surface is shaped like a saddle

59. Saddle Joints
The best example of a saddle joint in the body are the carpo-metacarpal joints of the thumb
Saddle
Joint

60. Ball and Socket Joint
The spherical head of one bone articulates with the cuplike socket of another
These joints are multiaxial and the most freely moving synovial joints

61. Ball and Socket Joints Movements in all planes is allowed
All axis and planes
Examples
Shoulder
Hip
Head of
Femur fits
Acetabulum
Of pelvis

65. Shoulder (Glenohumeral) Joint
The shoulder joint has sacrificed stability for mobility

66. Shoulder (Glenohumeral) Joint
The glenoid labrum deepens the cavity
The articular capsule is thin and loose to contribute to movement

67. Shoulder (Glenohumeral) Joint
Ligaments reinforce primarily the anterior aspect
Coracohumeral
Glenohumeral
Transverse humeral

68. Shoulder (Glenohumeral) Joint
Muscles crossing the joint provide most of the stability
Long head of the biceps is the most important stabilizer

69. Shoulder (Glenohumeral) Joint
Four tendons of the rotator cuff encircle the joint, blend with the capsule
Subscapularis
Supraspinatus
Infraspinatus
Teres minor

70. Shoulder Joint
The joint lacks structural stability and shoulder dislocations are quire common
Since the shoulder is weakest anteriorly and inferiorly, the humerous tends to dislocate forward and downward

71. Hip Joint
This ball and socket joint has good range of motion but the motion is limited by the deep socket and the joint ligaments
Deep acetabulum is enhanced by circular acetabular labrum
Ligamentum teres provides internal support to the joint

72. Hip Joint
This ball and socket joint has good range of motion but the motion is limited by the deep socket and the joint ligaments
Deep acetabulum is enhanced by circular acetabular labrum
Ligamentum teres provides internal to the joint

73. Hip Joint Thick articular capsule encloses the joint
Several strong ligaments support the joint
Iliofemoral, Pubofemoral, Ischiofemoral
Ligaments are arranged in such a manner that they screw the head of the femur into the acetabulum when standing erect

74. Elbow Joint
The ulna and humerus provide a stable hinge joint that allow flexion and extension
The Annular ligament anchors the head of the radius
Supported laterally and medially by ligaments

75. Knee Joint Largest and most complex joint
Allows for flexion extension and some rotation
C-shaped menisci deepen the tibial articular surface
Menisci prevent side to side rocking and act a shock absorbers

76. Knee Joint
The intracapsular ligaments of the knee cruciates are located within the intercondylar notch
Ligaments restrict anterior / posterior displacement
Ligaments are named for their tibial attachment sites

77. Knee Joint
Posteriorly the joint is reinforced by the oblique popliteal ligament
Gastrocnemius has two head that cross the joint posteriorly and provide dynamic stability

78. Analysis of Knee Movements
Weight bearing begins with the femur sliding posteriorly on the posterior aspect of the condyles
During extension the femoral condyles travel forward until restricted by the anterior cruciate ligament
Finally the lateral condyle stops before the medial spinning the joint into a locked position

79. Analysis of Knee Movements
When extending the knee as in kicking the same movements occur but in this case the tibia does the moving

80. Analysis of Knee Injuries
Knee is vulnerable to horizontal forces or high tension twisting movements
These factors lead to
Isolated meniscus tears
Isolated medial collateral ligament tears
Isolated cruciate tears
Triad of O’Donahue

81. Orthopedic Injuries to Joints
Sprains - Ligament supporting a joint are stretched or torn
Strains - Tendons or muscle fibers are stretched or torn
Cartilage - Tear or fragmentation of the cartilaginous tissue
Dislocation - Bones are forced out of their normal alignments at a joint
Bursitis/Tendonitis - Inflammation caused by trauma or more frequently overuse

82. Degenerative Conditions of Joints
Arthritis
A general reference to over 100 different types of inflammatory or degenerative diseases of the joints
Osteoarthritis
A degenerative disease related to the aging process (wear-and-tear arthritis)
Rheumatoid Arthritis
A chronic inflammatory disorder alters the synovival membrane
Can lead to changes in articular cartilage and bone tissue of the joints

83. Degenerative Conditions of Joints
Gouty Arthritis
Abnormal amount of Uric acid contribute to the deposition of urate crystals in the soft tissues of joints
Lead to agonizingly painful joints
If untreated can lead to fusion and immobilization of the joint

84. End of Chapter
Chapter 8