Joints (Articulations)
• Weakest parts of the skeleton
• Articulation – site where two or more
bones meet
• Functions of joints
– Give the skeleton mobility
– Hold the skeleton together
Classification of Joints:
Structural
• Structural classification focuses on the
material binding bones together and
whether or not a joint cavity is present
• The three structural classifications are:
– Fibrous
– Cartilaginous
– Synovial
Classification of Joints:
Functional
• Functional classification is based on the
amount of movement allowed by the joint
• The three functional classes of joints are:
– Synarthroses – immovable
– Amphiarthroses – slightly movable
– Diarthroses – freely movable
Fibrous Structural Joints
•
•
•
•
The bones are joined by fibrous tissues
There is no joint cavity
Most are immovable
There are three types – sutures,
syndesmoses, and gomphoses
Fibrous Structural Joints:
Sutures
• Occur between the bones of the skull
• Comprised of interlocking junctions
completely filled with connective tissue
fibers
• Bind bones tightly together, but allow for
growth during youth
• In middle age, skull bones fuse and are
called synostoses
Fibrous Structural Joints: Sutures
Figure 8.1a
Fibrous Structural Joints:
Syndesmoses
• Bones are connected by a fibrous tissue
ligament
• Movement varies from immovable to
slightly variable
• Examples include the connection between
the tibia and fibula, and the radius and
ulna
Fibrous Structural Joints:
Syndesmoses
Figure 8.1b
Fibrous Structural Joints:
Gomphoses
• The peg-in-socket fibrous joint between a
tooth and its alveolar socket
• The fibrous connection is the periodontal
ligament
Cartilaginous Joints
• Articulating bones are united by cartilage
• Lack a joint cavity
• Two types – synchondroses and
symphyses
Cartilaginous Joints:
Synchondroses
• A bar or plate of hyaline cartilage unites
the bones
• All synchondroses are synarthrotic
• Examples include:
– Epiphyseal plates of children
– Joint between the costal cartilage of the first
rib and the sternum
Cartilaginous Joints:
Synchondroses
Figure 8.2a, b
Cartilaginous Joints:
Symphyses
• Hyaline cartilage covers the articulating
surface of the bone and is fused to an
intervening pad of fibrocartilage
• Amphiarthrotic joints designed for strength
and flexibility
• Examples include intervertebral joints and
the pubic symphysis of the pelvis
Cartilaginous Joints:
Symphyses
Figure 8.2c
Synovial Joints
• Those joints in which the articulating
bones are separated by a fluid-containing
joint cavity
• All are freely movable diarthroses
• Examples – all limb joints, and most joints
of the body
Synovial Joints: General Structure
• Synovial joints all have the following
– Articular cartilage
– Joint (synovial) cavity
– Articular capsule
– Synovial fluid
– Reinforcing ligaments
Synovial Joints: General Structure
Figure 8.3a, b
Synovial Joints: Friction-Reducing
Structures
• Bursae – flattened, fibrous sacs lined with
synovial membranes and containing
synovial fluid
• Common where ligaments, muscles, skin,
tendons, or bones rub together
• Tendon sheath – elongated bursa that
wraps completely around a tendon
Synovial Joints: Friction-Reducing Structures
Figure 8.4
Synovial Joints: Stability
• Stability is determined by:
– Articular surfaces – shape determines what
movements are possible
– Ligaments – unite bones and prevent
excessive or undesirable motion
• Muscle tone is accomplished by:
– Muscle tendons across joints acting as
stabilizing factors
– Tendons that are kept tight at all times by
muscle tone
Synovial Joints: Movement
• The two muscle attachments across a joint
are:
– Origin – attachment to the immovable bone
– Insertion – attachment to the movable bone
• Described as movement along transverse,
frontal, or sagittal planes
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
Gliding Movements
• One flat bone surface glides or slips over
another similar surface
• Examples – intercarpal and intertarsal
joints, and between the flat articular
processes of the vertebrae
Angular Movement
• Flexion — bending movement that
decreases the angle of the joint
• Extension — reverse of flexion; joint angle
is increased
• Dorsiflexion and plantar flexion — up and
down movement of the foot
• Abduction — movement away from the
midline
• Adduction — movement toward the
midline
Gliding Movement
Figure 8.5a
Angular Movement
Figure 8.5b
Angular Movement
Figure 8.5c, d
Angular Movement
Figure 8.5e, f
Rotation
• The turning of a
bone around its
own long axis
• Examples
– Between first two
vertebrae
– Hip and shoulder
joints
Figure 8.5g
Special Movements
•
•
•
•
•
Supination and pronation
Inversion and eversion
Protraction and retraction
Elevation and depression
Opposition
Special Movements
Figure 8.6a
Special Movements
Figure 8.6b
Special Movements
Figure 8.6c
Special Movements
Figure 8.6d
Special Movements
Figure 8.6e
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
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
Types of Synovial Joints
Figure 8.7b
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
Pivot Joints
Figure 8.7c
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
Condyloid, or Ellipsoidal, Joints
Figure 8.7d
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
Saddle Joints
Figure 8.7e
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
Ball-and-Socket Joints
Figure 8.7f
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
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
Figure 8.8c
Synovial Joints: Knee –
Other Supporting Structures
•
•
•
•
Anterior cruciate ligament
Posterior cruciate ligament
Medial meniscus (semilunar cartilage)
Lateral meniscus
Synovial Joints: Knee –
Other Supporting Structures
Figure 8.8b
Synovial Joints: Knee –
Posterior Superficial View
• Adductor magnus
tendon
• Articular capsule
• Oblique popliteal
ligament
• Arcuate popliteal
ligament
• Semimembranosus
tendon
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
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
Synovial Joints: Shoulder Stability
Figure 8.10a
Synovial Joints: Shoulder Stability
Figure 8.10b
Synovial Joints: 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 and strong ligaments
Synovial Joints: Hip Stability
• Acetabular
labrum
• Iliofemoral
ligament
• Pubofemoral
ligament
• Ischiofemoral
ligament
• Ligamentum
teres
Figure 8.11a
Synovial Joints: Hip Stability
Figure 8.11c, d
Synovial Joints: Elbow
• Hinge joint that allows flexion and
extension only
• Radius and ulna articulate with the
humerus
Synovial Joints: Elbow Stability
• Annular ligament
• Ulnar collateral ligament
• Radial collateral ligament
Figure 8.12a
Synovial Joints: Elbow Stability
Figure 8.12b, d
Sprains
• The ligaments reinforcing a joint are
stretched or torn
• Partially torn ligaments slowly repair
themselves
• Completely torn ligaments require prompt
surgical repair
Cartilage Injuries
• The snap and pop of overstressed
cartilage
• Common aerobics injury
• Repaired with arthroscopic surgery
Dislocations
• 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
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
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
Osteoarthritis (OA)
• Most common chronic arthritis; often
called “wear-and-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
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
Osteoarthritis: Treatments
• OA is slow and irreversible
• Treatments include:
– Mild pain relievers, along with moderate
activity
– Magnetic therapy
– Glucosamine sulfate decreases pain and
inflammation
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
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
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
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