1. Chapter 8 Joints

2. Joints (Articulations)
Articulation—site where two or more bones meet
Functions of joints:
Give skeleton mobility
Hold skeleton together

3. Functional Classification of Joints
Based on amount of movement allowed by the joint
Three functional classifications:
Synarthroses—immovable
Amphiarthroses—slightly movable
Diarthroses—freely movable
Synarthroses – sutures of the skull
Amphiarthroses – vertebral bodies
Diarthroses - glenohumeral

4. Structural Classification of Joints
Based on material binding bones together and whether or not a joint cavity is present
Three structural classifications:
Fibrous
Cartilaginous
Synovial
Fibrous joints – sutures, syndemoses, and gomphoses joints –
Bones joined by dense fibrous connective tissue
No joint cavity
Most are synarthrotic (immovable)

5. Fibrous Joints: Sutures
Rigid, interlocking joints containing short connective tissue fibers
Allow for growth during youth
In middle age, sutures ossify and are called synostoses

6. Fibrous Joints: Syndesmoses
Bones connected by ligaments (bands of fibrous tissue)
Movement varies from immovable to slightly movable
Examples:
Synarthrotic distal tibiofibular joint
Diarthrotic interosseous connection between radius and ulna

7. Fibrous Joints: Gomphoses
Peg-in-socket joints of teeth in alveolar sockets
Fibrous connection is the periodontal ligament

8. Bones united by cartilage No joint cavity Two types:
Cartilaginous Joints
Bones united by cartilage
No joint cavity
Two types:
Synchondroses – typically epiphyseal plates
Symphyses – pubic symphysis
Synchondroses
A bar or plate of hyaline cartilage unites the bones
All are synarthrotic
Symphyses
Hyaline cartilage covers the articulating surfaces and is fused to an intervening pad of fibrocartilage
Strong, flexible amphiarthroses

9. Synovial Joints Distinguishing features:
Articular cartilage: hyaline cartilage
Joint (synovial) cavity: small potential space
Articular (joint) capsule
Outer fibrous capsule and an inner synovial membrane
Synovial fluid:
Viscous slippery filtrate of plasma + hyaluronic acid
Lubricates and nourishes articular cartilage
Three possible types of reinforcing ligaments:
Capsular (intrinsic)—part of the fibrous capsule
Extracapsular—outside the capsule
Intracapsular—deep to capsule; covered by synovial membrane
Rich nerve and blood vessel supply:
Nerve fibers detect pain, monitor joint position and stretch
Capillary beds produce filtrate for synovial fluid
All are diarthrotic
Include all limb joints; most joints of the body

10. Ligament Joint cavity (contains synovial fluid) Articular (hyaline)
cartilage
Fibrous
capsule
Articular
capsule
Synovial
membrane
Periosteum
Figure 8.3

11. Synovial Joints: Friction-Reducing Structures
Bursae:
Flattened, fibrous sacs lined with synovial membranes
Contain synovial fluid
Commonly act as “ball bearings” where ligaments, muscles, skin, tendons, or bones rub together

12. Synovial Joints: Friction-Reducing Structures
Tendon sheath:
Elongated bursa that wraps completely around a tendon

13. Stabilizing Factors at Synovial Joints
Shapes of articular surfaces (minor role)
Ligament number and location (limited role)
Muscle tone, which keeps tendons that cross the joint taut
Extremely important in reinforcing shoulder and knee joints and arches of the foot

14. Synovial Joints: Movement
Muscle attachments across a joint:
Origin—attachment to the immovable bone
Insertion—attachment to the movable bone
Muscle contraction causes the insertion to move toward the origin
Movements occur along transverse, frontal, or sagittal planes

15. 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

16. Summary of Characteristics of Body Joints
Consult Table 8.2 for:
Joint names
Articulating bones
Structural classification
Functional classification
Movements allowed

17. Movements at Synovial Joints
Gliding
Angular movements:
Flexion, extension, hyperextension
Abduction, adduction
Circumduction
Rotation
Medial and lateral rotation
Gliding – One flat bone surface glides or slips over another similar surface
Examples:
Intercarpal joints
Intertarsal joints
Between articular processes of vertebrae

18. Movements at Synovial Joints
4. Special movements
Supination, pronation
Dorsiflexion, plantar flexion of the foot
Inversion, eversion
Protraction, retraction
Elevation, depression
Opposition

19. Angular Movements
Movements that occur along the sagittal plane:
Flexion—decreases the angle of the joint
Extension— increases the angle of the joint
Hyperextension—excessive extension beyond normal range of motion

20. Angular Movements
Movements that occur along the frontal plane:
Abduction—movement away from the midline
Adduction—movement toward the midline
Circumduction—flexion + abduction + extension + adduction of a limb so as to describe a cone in space

21. The turning of a bone around its own long axis Examples:
Rotation
The turning of a bone around its own long axis
Examples:
Between C1 and C2 vertebrae
Rotation of humerus and femur

22. Movements of radius around ulna:
Special Movements
Movements of radius around ulna:
Supination (turning hand backward)
Pronation (turning hand forward)

23. Special Movements Movements of the foot:
Dorsiflexion (upward movement)
Plantar flexion (downward movement)

24. Special Movements Movements of the foot:
Inversion (turn sole medially)
Eversion (turn sole laterally)

25. Movements in a transverse plane:
Special Movements
Movements in a transverse plane:
Protraction (anterior movement)
Retraction (posterior movement)

26. Special Movements
Elevation (lifting a body part superiorly)
Depression (moving a body part inferiorly)

27. Opposition of the thumb
Special Movements
Opposition of the thumb
Movement in the saddle joint so that the thumb touches the tips of the other fingers

28. Classification of Synovial Joints
Six types, based on shape of articular surfaces:
Plane
Hinge
Pivot
Condyloid
Saddle
Ball and socket

29. Plane Joints
Nonaxial joints
Flat articular surfaces
Short gliding movements
Ex. Intercarpal Joint

30. Hinge Joints
Uniaxial joints
Motion along a single plane
Flexion and extension only

31. Pivot Joints
Rounded end of one bone conforms to a “sleeve,” or ring of another bone
Uniaxial movement only

32. Condyloid (Ellipsoidal) Joints
Biaxial joints
Both articular surfaces are oval
Permit all angular movements

33. Allow greater freedom of movement than condyloid joints
Saddle Joints
Biaxial
Allow greater freedom of movement than condyloid joints
Each articular surface has both concave and convex areas
Ex. Thumbs (Carpo-metacarpal joints)

34. Ball-and-Socket Joints
Multiaxial joints
The most freely moving synovial joints

35. Knee Joint Largest, most complex joint of body
Three joints surrounded by a single joint cavity:
Femoropatellar joint:
Plane joint
Allows gliding motion during knee flexion
Lateral and medial tibiofemoral joints between the femoral condyles and the C-shaped lateral and medial menisci (semilunar cartilages) of the tibia
Allow flexion, extension, and some rotation when knee is partly flexed

36. Knee Joint At least 12 associated bursae
Capsule is reinforced by muscle tendons:
E.g., quadriceps and semimembranosus tendons
Joint capsule is thin and absent anteriorly
Anteriorly, the quadriceps tendon gives rise to:
Lateral and medial patellar retinacula
Patellar ligament

37. Capsular and extracapsular ligaments
Knee Joint
Capsular and extracapsular ligaments
Help prevent hyperextension
Intracapsular ligaments:
Anterior and posterior cruciate ligaments
Prevent anterior-posterior displacement
Reside outside the synovial cavity

38. Lateral knee injury

39. Shoulder (Glenohumeral) Joint
Ball-and-socket joint: head of humerus and glenoid fossa of the scapula
Stability is sacrificed for greater freedom of movement

40. Reinforcing ligaments:
Shoulder Joint
Reinforcing ligaments:
Coracohumeral ligament—helps support the weight of the upper limb
Three glenohumeral ligaments—somewhat weak anterior reinforcements

41. Shoulder joint Reinforcing muscle tendons:
Tendon of the long head of biceps:
Travels through the intertubercular groove
Secures the humerus to the glenoid cavity
Four rotator cuff tendons encircle the shoulder joint:
Subscapularis
Supraspinatus
Infraspinatus
Teres minor

42. Elbow Joint
Radius and ulna articulate with the humerus
Hinge joint formed mainly by trochlear notch of ulna and trochlea of humerus
Flexion and extension only

43. Anular ligament—surrounds head of radius
Elbow Joint
Anular ligament—surrounds head of radius
Two capsular ligaments restrict side-to-side movement:
Ulnar collateral ligament
Radial collateral ligament

44. Hip (Coxal) Joint
Ball-and-socket joint
Head of the femur articulates with the acetabulum
Good range of motion, but limited by the deep socket
Acetabular labrum—enhances depth of socket

45. Hip Joint Reinforcing ligaments: Iliofemoral ligament
Pubofemoral ligament
Ischiofemoral ligament
Ligamentum teres

46. Common Joint Injuries Sprains Cartilage tears
The ligaments are stretched or torn
Partial tears slowly repair themselves
Complete ruptures require prompt surgical repair
Cartilage tears
Due to compression and shear stress
Fragments may cause joint to lock or bind
Cartilage rarely repairs itself
Repaired with arthroscopic surgery

48. Common Joint Injuries Dislocations (luxations)
Occur when bones are forced out of alignment
Accompanied by sprains, inflammation, and joint immobilization
Caused by serious falls or playing sports
Subluxation—partial dislocation of a joint

49. Inflammatory and Degenerative Conditions
Bursitis
An inflammation of a bursa, usually caused by a blow or friction
Treated with rest and ice and, if severe, anti-inflammatory drugs
Tendonitis
Inflammation of tendon sheaths typically caused by overuse
Symptoms and treatment similar to bursitis

50. Arthritis
>100 different types of inflammatory or degenerative diseases that damage joints
Most widespread crippling disease in the U.S.
Symptoms; pain, stiffness, and swelling of a joint
Acute forms: caused by bacteria, treated with antibiotics
Chronic forms: osteoarthritis, rheumatoid arthritis, and gouty arthritis

51. Osteoarthritis (OA)
Common, irreversible, degenerative (“wear-and-tear”) arthritis
85% of all Americans develop OA, more women than men
Probably related to the normal aging process

52. Osteoarthritis (OA)
More cartilage is destroyed than replaced in badly aligned or overworked joints
Exposed bone ends thicken, enlarge, form bone spurs, and restrict movement
Treatment: moderate activity, mild pain relievers, capsaicin creams, glucosamine and chondroitin sulfate

53. Rheumatoid Arthritis (RA)
Chronic, inflammatory, autoimmune disease of unknown cause
Usually arises between age 40 and 50, but may occur at any age; affects 3 times as many women as men
Signs and symptoms include joint pain and swelling (usually bilateral), anemia, osteoporosis, muscle weakness, and cardiovascular problems

54. Rheumatoid Arthritis
RA begins with synovitis of the affected joint
Inflammatory blood cells migrate to the joint, release inflammatory chemicals
Inflamed synovial membrane thickens into a pannus
Pannus erodes cartilage, scar tissue forms, articulating bone ends connect (ankylosis)

55. Figure 8.15