JOINTS (Arthrology)
• Flexible connective tissue form joints that hold
bones together ,while still permitting some
motion
• A joint, also called articulation or arthosis is a
point of contact between two bones, a bone
and cartilage or bone and teeth
• The scientific study of joints is called
arthrology.
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Joint Classification
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The joints are classified in two different ways:
Based on their structure-Structural Classification
Based on their function: Functional Classification
The structural classification is based on two
criteria
1)The presence or absence of a space between
articulating bones called synovial cavity
2)The type of connective tissue that binds the
bones together
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Joint Classification
• Structurally joints are classified as following:
– Fibrous joints : the bones are held together by
fibrous connective tissue that is rich in collagen
fibers. No synovial cavity.
– Cartilaginous joints: the bones are held together
by cartilage. No synovial cavity.
– Synovial joints: the bones forming the joint have a
synovial cavity and are united by dense irregular
connective tissue.
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Joint Classification
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Functionally joints are classified as following:
Synarthosis: An immovable joint
Amphiarthosis: A slightly movable joint
Diarthosis: A freely movable joint. All
Diarthosis are synovial joints. They have a
variety of shapes and permit several different
types of movements
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Fibrous Joints
• These are joints that lack a synovial cavity and
the articulating bones are held very closely
together by fibrous connective tissue. They
permit little or no movement. They are further
classified in three types:
– Sutures
– Syndesmoses
– Gomphoses
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Types of Fibrous Joints
– Sutures: thin layer of dense connective issue. Unites
bones of the skull.
– E.g. coronal suture between parietal and frontal bones
– The irregular interlocking of sutures give them
additional strength and decrease the changes of
fracture
– Because a suture is immovable, it is functionally
classified as a synarthrosis.
– Some sutures are replaced by bone in the adult.
Such a suture is called synostosis. (or a joint in which
there is complete fusion of two separate bones in one
bone)
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Types of Fibrous Joints
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Types of Fibrous Joints
– Syndesmoses: there is a greater distance between
the bones and more fibrous connective tissue. The
tissue is either arranged as a bundle (ligament) or
as a sheet (interosseous membrane).
– Example: distal tibiofibular joint where anterior
tibiofibular ligament connects the joint also the
interosseous membrane between parallel borders
of tibia and fibula
– Because it permits slight movement, a
syndesmosis is classified functionally as an
amphiarthrosis.
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Types of Fibrous Joints
• Gomphoses- this is a type of fibrous joint in
which a cone-shaped peg fits into a socket.
The only example are the articulations of the
roots of the teeth with the sockets of the
alveolar processes of the maxillae and
mandible. The dense fibrous connective
tissue is called the periodonatal ligament.
This is functionally classified as a synarthrosis.
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Cartilaginous Joints
• This also lacks a synovial cavity and permits
little or no movement.
• Bones are connected by a hyaline cartilage or
fibrocartilage
• These are further divided into :
– Synchondroses
– Symphyses
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Types of Cartilaginous Joints
– Synchondroses: here the connecting material is
hyaline cartilage. Example is the joint between the
first rib and manubrium of the sternum.
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Types of Cartilaginous Joints
• Symphyses: here the ends of the articulating
bones are covered with hyaline cartilage but
the bones are connected by a broad flat disc
of fibrocartilage.
• All symphyses occur in the midline of the body
• Examples: pubic symphysis, junction of the
manubrium and sternum, intervertebral
joints. Functionally, this is an amphiarthrosis,
a slightly movable joint.
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Synovial Joints
• The unique characteristic of a synovial joint is presence
of a space called synovial cavity between articulating
bones
• Because the synovial joint allows the joint to be freely
movable all synovial joints are classified as diarthoses
• The bones of synovial joint are covered by a layer of
hyaline cartilage called articular cartilage
• The cartilage covers the articulating surface of the
bone with a smooth slippery surface but does not bind
them together
• It also helps to reduce friction between the joint during
movement and help to absorb shock
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Synovial Joints
• Articular Capsule: A sleeve like articular capsule
surrounds the synovial joint and unites the
articulating bones
• It is composed of two layers a fibrous capsule
usually consist of irregular dense connective
tissue that attaches to the periosteum of
articulating bone
• The flexibility of this capsule permits considerable
movements ,while its tensile strength helps the
bones from dislocation
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Synovial Joints
• The inner layer of this articular capsule is a
synovial membrane which is composed of
areolar connective tissue and elastic fibers
• At many synovial joints the synovial
membrane includes accumulations of adipose
tissue called articular fat pad e.g. knee joint
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Synovial Joints
• Synovial Fluid: The synovial membrane secretes
synovial fluid ,a viscous clear or pale yellow fluid
• It forms a thin film over the surfaces with
articular capsule
• Its functions include reducing friction by
lubricating the joint, absorbing shock ,supplying
o2 and nutrients to and removing co2 and
metabolic waste from chondrocytes within
articular cartilage
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Synovial Joints
• Bursae and Tendon Sheaths: The various
movements of the body create friction between
the moving parts
• Saclike structures called bursae are situated to
alleviate friction in some joints like knee and
shoulder
• They are filled with a small amount of fluid like
the synovial fluid
• Tendon Sheaths also reduce friction at joints, they
wrap around certain tendons that produce
friction.
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Synovial Joints
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Types of Synovial Joints
• Planar joints
• Hinge Joints
• Pivot Joints
• Condyloid Joints
• Saddle Joints
• Ball-and-Socket Joints-
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Types of Synovial Joints
• Planar joints- the articulating surfaces are flat
or slightly curved.
• Planar joints permit gliding movements
• These joints are said to be non axial because
the motion they allow does not occur around
an axis or around a plane
• Example are intercarpal joints, intertarsal
joints, sternoclavicular joints,
acromioclavicular joints, sternocostal joints,
vertebrocostal joints.
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Types of Synovial Joints
• Hinge Joints-the convex surface of one fits into
the concave surface of another.
• The hinge joint produces an angular opening and
closing motion like that of a hinged door
• In most joints one bone remains in a fixed
position while the other moves around an axis
• These as monoaxial as they allow motion around
a single axis
• Hinge joint permit only flexion and extension
• Eg. Knee, elbow, ankle, interphalangeal. Monaxial
(uniaxial).
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Trochlea
humerus
Trochlear
notch
ulna
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Types of Synovial Joints
• Pivot Joints-here the rounded or pointed surface of
one bone articulates with a ring formed partly by
another bone and partly by a ligament.
• This is monaxial ,as it allows rotation only around its
own longitudinal axis
• Examples atlanto-axial joint,
radioulnar joint :turns palm anteriorly and posteriorly.
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Angular ligament
Head Of radius
Radius
ulna
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Types of Synovial Joints
• Condyloid Joints-also called ellipsoidal joint. The convex ovalshaped projection of one fits into the oval-shaped depression
of another.
• A condyloid joint is a biaxial joint because it permits
movements around around two axis
• It allows flexion,Extension,Adduction,Abduction and
circumduction
• Eg. Wrist and metacarpophalangeal joints. Biaxial.
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Types of Synovial Joints
• Saddle Joints-here the articular surface of one
bone is saddle-shaped and the articular
surface of the other fits into the “saddle”.
• Saddle joint is biaxial joint because it permits
movements around around two axis
• It allows flexion,Extension,Adduction,Abduction and
circumduction
• Eg. Carpometacarpal joint. Biaxial.
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Types of Synovial Joints
• Ball-and-Socket Joints- this consists of the
ball-like surface of one bone fitting into a
cuplike depression of another bone.
• These joints are multiaxial as they permit
movement about three axis
• It allows flexion,Extension,Adduction,Abduction and
circumduction and rotation
• Egs. Shoulder and hip joints.
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Glenoid Cavity of
Scapula
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Types of Movements
• Gliding: This is a simple movement in which
relatively flat bone surfaces move side-to-side
and back-and-forth with respect to one
another
• There is no significant alteration of angle
between the bones
• E.g. Intercarpal and Intertarsal joint
• Angular movements: Four angular
movements may occur in various diarthrodial
joints: flexion, extension, abduction, and
adduction (F7.8). Angular movements increase
Types of Movements
• FLEXION When a bone is moved in an
anterior-posterior plane in such a manner as
to decrease the angle between it and its
adjoining bone, flexion occurs. Examples
include bending the elbow, bringing the thigh
towards the abdomen, and bringing the calf of
the leg toward the back of the thigh. Pulling
the heel upward, thus lowering the toe region
of a foot, is referred to as plantar flexion.
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Types of Movements
EXTENSION Extension is the opposite of flexion. It causes the angle between
adjoining bones to increase. Extension occurs when a flexed joint is moved back to
the anatomical position, such as straightening the arm, thigh, and knee.
Hyperextension occurs when the part is moved beyond the straight position, such
as arching the back or bringing the limbs posteriorly beyond the plane of the body.
Raising the toe region toward the shin is often considered to be extension of the
foot, but is called dorsiflexion.
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Types of Movements
• ABDUCTION When a part, such as a limb, is
moved away from the midline of the body,
abduction occurs. In the case of the fingers
and toes, abduction involves moving them
away from the midline of the hand or foot.
• ADDUCTION Adduction, the reverse of
abduction, involves the movement of a part
toward the midline of the body, back toward
the anatomical position. In the case of the
fingers and toes, the movement is toward the
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Types of Movements
• Circular Movements
• In addition to the four angular movements,
four circular movements are allowed by some
diarthrodial joints: circumduction, rotation,
supination, and F7.8 pronation (F7.8)
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Types of Movements
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• CIRCUMDUCTION The joint motion known as circumduction
delineates a cone. The base of the cone is outlined by the
movement of the distal end of the bone, with the apex of the cone
Iying in the articular cavity. The movement is actually a sequential
combination of flexion, abduction, extension, and adduction.
Circumduction is common at the hip and the shoulder joints, and is
possible in other joints also.
• ROTATION The motion of a bone around a central axis is rotation. If
the anterior surface of a bone such as the humerus or femur moves
inward, it is called inward (medial) rotation. When the anterior
surface turns outward it is outward (lateral) rotation.
Types of Movements
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Types of Movements
• SUPINATION The term used to describe the
outward rotation of the forearm, causing the
palms to face upward or forward and the
radius and the ulna to be parallel, is
supination. The forearms are supinated in the
anatomical position.
• PRONATION The term used to describe the
inward rotation of the forearm, causing the
radius to cross diagonally over the ulna and
the palms to face downward or backward, is
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Types of Movements
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Types of Movements
• Special Movements
• Several special movements cannot be
described as either angular or circular. These
movements are elevation, depression,
inversion, eversion, protraction, and
retraction.
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Types of Movements
• ELEVATION The motion that raises a part is
elevation. This term is most commonly used to
refer to the raising of the scapula, as when
shrugging the shoulders, or raising the
mandible, as when closing the mouth.
• DEPRESSION The motion that lowers a part is
depression. This term is often used to refer to
the lowering of the scapula or the mandible.
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Types of Movements
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Types of Movements
• INVERSION The twisting of the foot so that the
sole faces inward with its inner margin raised
is inversion.
• EVERSION The twisting of the foot so that the
sole faces outward with its outer margin
raised is eversion.
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Types of Movements
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Types of Movements
• PROTRACTION The motion that moves a part,
such as the mandible, forward is protraction.
• RETRACTION The motion that returns a
protracted part to its usual position is
retraction
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Types of Movements
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