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Elements of Arthrology
Arthrology-study of joints
Arthritis- inflammation of the joint
Classification of joints
Degree of movement
Joining material
Degree of movement
i. Synarthrotic joint- no movements e.g
ii.Amphyarthrotic joints-limited
movements
iii. Diarthrotic joints- free movements
Joining material
i. Fibrous joints
ii. Cartilaginous joints
iii. Synovial joints
Fibrous joints
Articulating bones are held by fibrous tissue.
Most joints are immovable. A few allow a
small degree of mobility. Degree of mobility
depends on the length of fibers (collagen)
uniting the articulating bones.
a)Sutures: Joints of skull bones. Edges of
articulating bone interlock and tightly held by
a thin layer of fibrous tissue.
b)Syndesmosis: Bones are held by a sheet of
fibrous tissue (ligament or interosseous
membrane) Unlike in sutures here there is
some degree of mobility. Examples:
radioulnar, tibiofibullar joints
c)Gomphosis: Peg-end-socket between the tooth
and mandible/maxilla
Suture joints
Fig. Synovial joint
Cartilaginous joints
Also called synchondrosis. Bones are united by hyaline
or a fibrocartilage.
a) Primary cartilaginous joint: Are united by hyaline
cartilage and permit no movement. Examples:
epiphyseal cartilage between the epiphysis and
diaphysis. Allows bone growth in young subject and
in the adult it’s replaced by bone; so a synchondrosis
is converted into synostosis. Another example is the
costochondral articulation of the sternum
b) Secondary cartilaginous joint: Also called
symphysis and situated in the axial skeleton.
Articulating material is a fibrocartilage. The bones
are covered by a thin hyaline cartilage. The joints are
strong and slightly movable. Examples are pubic
symphysis, intervetebral discs and the
manubrium sterni.
Synovial joints
• Common types of joints responsible for the various
movements we perform.
• The bones are held by a fibrous capsule which
encloses a joint cavity. Ligaments/tendons inside or
outside the capsule strengthen the joint.
• A synovial membrane lines the joint cavity. The
membrane has cells that secrete synovial fluid
(synovia) into the joint cavity for lubrication.
• Articulating surfaces are lined by a thin hyaline
cartilage.
• Some joints may be traversed an articular disc
temporomandibular, sternoclavicular,
acromioclavicular, radioulnar and knee joints. The
disc attached to the joint capsule.
Types of synovial joints
i) Plane joints: Flat articular surfaces which permit
gliding/slipping or twisting of one bone on the
other. E.g. intercarpal, intertarsals,
acromioclavicular, sternoclavicular joints.
ii) Hinge (ginglymus) joints: Uniaxial joints
permitting flexion and extension) The articulating
surface of bones is concave and that of the other
bone is convex. E.g elbow, ankle, knee and
interphalangeal joints
iii) Pivot joints: Also uniaxial permitting rotational
movement. A rounded piece of bone rotates within
a ring made up of bone and strong ligaments. E.g
proximal radioulnar and atlanto-axial joints.
Types of synovial joints
iv) Condyloid joints: Biaxial joints permitting extension,
flexion and abduction, adduction movements. Have two
convex articular surfaces that articulate with two concave
surfaces. E.g metacapophalangeal, metatarsaophalangeal,
atlanto-occipital joints.
v) Ellipsoid joints: Also biaxial; allow flexion, extension,
abduction and adduction movements. One surface of
articulating bone is oval and another is a socket. E.g
(radiocarpal) joint.
vi) Saddle joints: Articulating bones are concave and
convex opposite to one another. Multiaxial joints which
allow movements back and forth and up and down but
does not allow rotation movement. E.g. carpo-metacarpal
joint of the thumb.
vii) Ball and socket joints: Multiaxia joint that allow
flexion, extension, abduction, adduction, rotation and
circumduction. E.g. shoulder and hip joints.
Joints
Saddle
Pivot
Joints
Ellipsoid
Condyloid
Joint stability
i) Articulating surfaces: Bone shape plays an
important role in joint stability; e.g a concave
socket and a convex head form a stable joint
such as the hip joint.
ii) Ligaments: Fibrous or elastic ligaments
stabilize joints.
iii) Muscle tone: Muscle tone around a joint
control stability E.g rotator cuff muscles and
qadriceps femoris stabilize elibow and knee
joints
Related structures
• Bursa: Small fluid-filled sac located at the
point where a muscle or tendon slides
across bone. Bursae serve to reduce
friction between the two moving surfaces.
The synovial fluid in the bursa moistens
the interior of the bursa.
• Synovial Sheath: A synovial sheath is a
flat bursa that surrounds certain tendons
particularly in the hands and feet
Hilton’s law
A Nerve that innervates a joint also
innervates the muscles that move the
joint and the skin that covers the distal
attachments of the muscles