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Joints
Part B
Human Anatomy & Physiology, Sixth Edition
Elaine N. Marieb
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8
Joints
 Although all synovial joints have structural features in
common they do not have a common structural plan.
 Base on the shape of the articular surfaces can be
classified in 6 major categories:
 1.- Planes
 2.- Hinge
 3.- Pivot
 4.- Condyloid
 5.- Saddle
 6.- Ball and socked joints
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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
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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
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Types of Synovial Joints
Figure 8.7b
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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
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Pivot Joints
Figure 8.7c
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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
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Condyloid, or Ellipsoidal, Joints
Figure 8.7d
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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
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Saddle Joints
Figure 8.7e
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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
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Ball-and-Socket Joints
Figure 8.7f
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Synovial Joints: Knee
 Largest and most complex joint of the body
 Allows flexion, extension, and some rotation
 Three joints in one surrounded by a single joint
cavity
 Femoropatellar
 Lateral and medial tibiofemoral joints
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Synovial Joints: Knee Ligaments and Tendons –
Anterior View
 Tendon of the
quadriceps femoris
muscle
 Lateral and medial
patellar retinacula
 Fibular and tibial
collateral ligaments
 Patellar ligament
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Figure 8.8c
Synovial Joints: Knee –
Other Supporting Structures
 Anterior cruciate ligament
 Posterior cruciate ligament
 Medial meniscus (semilunar cartilage)
 Lateral meniscus
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Synovial Joints: Knee –
Other Supporting Structures
Figure 8.8b
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Synovial Joints: Knee –
Posterior Superficial View
 Adductor magnus
tendon
 Articular capsule
 Oblique popliteal
ligament
 Arcuate popliteal
ligament
 Semimembranosus
tendon
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Figure 8.8e
Synovial Joints: Shoulder (Glenohumeral)
 Ball-and-socket joint in which stability is sacrificed
to obtain greater freedom of movement
 Head of humerus articulates with the glenoid fossa
of the scapula
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Homeostatic Imbalance
 Lateral blows to the tibial collateral ligament and the
medial meniscus attached to it, as well as the
anterior cruciate ligament (Fig 8.9)
 50% football players have this injury
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Synovial Joints: Shoulder Stability
 Weak stability is maintained by:
 Thin, loose joint capsule
 Four ligaments – coracohumeral, and three
glenohumeral
 Tendon of the long head of biceps, which travels
through the intertubercular groove and secures the
humerus to the glenoid cavity
 Rotator cuff (four tendons) that encircles the
shoulder joint and blends with the articular capsule
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Synovial Joints: Shoulder Stability
Figure 8.10a
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Synovial Joints: Shoulder Stability
Figure 8.10b
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Synovial Joints: Hip (Coxal) Joint
 Hip joint like the shoulder is a ball-and-socket joint
 Head of the femur articulates with the acetabulum
 Good range of motion, but limited by the deep
socket and strong ligaments
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Synovial Joints: Hip Stability
 Acetabular
labrum
 Iliofemoral
ligament
 Pubofemoral
ligament
 Ischiofemoral
ligament
 Ligamentum
teres
Figure 8.11a
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Synovial Joints: Hip Stability
Figure 8.11c, d
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Synovial Joints: Elbow
 Our upper limbs are flexible extensions that permit
us to reach out and manipulate things in our
environment. Beside the shoulder joint the most
prominent of the upper limb joint is the elbow
 Hinge joint that allows flexion and extension only
 Radius and ulna articulate with the humerus
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Synovial Joints: Elbow Stability
 Annular ligament
 Ulnar collateral ligament
 Radial collateral ligament
Figure 8.12a
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Synovial Joints: Elbow Stability
Figure 8.12b, d
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Homeostatic Imbalance of joints (pp 272)
 The most common trauma-induces joint injuries are:
sprains and dislocations
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Sprains
 The ligaments reinforcing a joint are stretched or
torn
 Partially torn ligaments slowly repair themselves
 Completely torn ligaments require prompt surgical
repair
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Cartilage Injuries
 The snap and pop of overstressed cartilage
 Common aerobics injury
 Repaired with arthroscopic surgery
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Dislocations (luxations)
 Occur when bones are forced out of alignment
 Usually accompanied by sprains, inflammation, and
joint immobilization
 Caused by serious falls and are common sports
injuries
 Subluxation – partial dislocation of a joint
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Inflammatory and Degenerative Conditions
 Bursitis
 An inflammation of a bursa, usually caused by a blow or
friction
 Symptoms are pain and swelling
 Treated with anti-inflammatory drugs; excessive fluid may
be aspirated
 Tendonitis
 Inflammation of tendon sheaths typically caused by overuse
 Symptoms and treatment are similar to bursitis
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Arthritis
 More than 100 different types of inflammatory or
degenerative diseases that damage the joints
 Most widespread crippling disease in the U.S.
 Symptoms – pain, stiffness, and swelling of a joint
 Acute forms are caused by bacteria and are treated
with antibiotics
 Chronic forms include osteoarthritis, rheumatoid
arthritis, and gouty arthritis
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Osteoarthritis (OA)
 Most common chronic arthritis; often called “wearand-tear” arthritis
 Affects women more than men
 85% of all Americans develop OA
 More prevalent in the aged, and is probably related
to the normal aging process
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Osteoarthritis: Course
 OA reflects the years of abrasion and compression
causing increased production of metalloproteinase
enzymes that break down cartilage
 As one ages, cartilage is destroyed more quickly
than it is replaced
 The exposed bone ends thicken, enlarge, form bone
spurs, and restrict movement
 Joints most affected are the cervical and lumbar
spine, fingers, knuckles, knees, and hips
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Osteoarthritis: Treatments
 OA is slow and irreversible
 Treatments include:
 Mild pain relievers, along with moderate activity
 Magnetic therapy
 Glucosamine sulfate decreases pain and
inflammation
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Rheumatoid Arthritis (RA)
 Chronic, inflammatory, autoimmune disease of
unknown cause, with an insidious onset
 Usually arises between the ages of 40 to 50, but may
occur at any age
 Signs and symptoms include joint tenderness,
anemia, osteoporosis, muscle atrophy, and
cardiovascular problems
 The course of RA is marked with exacerbations and
remissions
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Rheumatoid Arthritis: Course
 RA begins with synovitis of the affected joint
 Inflammatory chemicals are inappropriately released
 Inflammatory blood cells migrate to the joint,
causing swelling
 Inflamed synovial membrane thickens into a pannus
 Pannus erodes cartilage, scar tissue forms,
articulating bone ends connect
 The end result, ankylosis, produces bent, deformed
fingers
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Rheumatoid Arthritis: Treatment
 Conservative therapy – aspirin, long-term use of
antibiotics, and physical therapy
 Progressive treatment – anti-inflammatory drugs or
immunosuppressants
 The drug Enbrel, a biological response modifier,
neutralizes the harmful properties of inflammatory
chemicals
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Gouty Arthritis
 Deposition of uric acid crystals in joints and soft
tissues, followed by an inflammation response
 Typically, gouty arthritis affects the joint at the base
of the great toe
 In untreated gouty arthritis, the bone ends fuse and
immobilize the joint
 Treatment – colchicine, nonsteroidal antiinflammatory drugs, and glucocorticoids
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Developmental Aspects of Joints
 By embryonic week 8, synovial joints resemble
adult joints
 Few problems occur until late middle age
 Advancing years take their toll on joints:
 Ligaments and tendons shorten and weaken
 Intervertebral discs become more likely to herniate
 Most people in their 70s have some degree of OA
 Prudent exercise (especially swimming) that coaxes
joints through their full range of motion is key to
postponing joint problems
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