Bones are too rigid to bend. Flexible connective tissues
from joints and permit movement.
A joint, also called articulation is a point of contact.
The scientific study of joints is called arthrology.
The study of the motion of the human body is called
Structurally joints are classified as following:
Fibrous joints : the bones are held together by fibrous
connective tissue that is rich in collagen fibers. No
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
Functionally, joints are classified as one of the
Synarthrosis: an immovable joint (skull).
Amphiarthrosis: a slightly movable joint (pelvis).
Diarthrosis: a freely movable joint. All diarthroses are
These are joints that lack a synovial cavity. They permit little or no
Sutures: thin layer of dense connective issue. Unites bones of the
skull. 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.
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
(interosseus membrane). Example tibia/fibula. Because it permits slight
movement, a syndesmosis is classified functionally as an amphiarthrosis.
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.
This also lacks a synovial cavity and permits little or no
Synchondroses: here the connecting material is hyaline
cartilage. An example is the epiphyseal plate that connects
the epiphysis and diaphysis of a growing bone. Another
example is the joint between the first rib and manubrium of
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. Examples: pubic
symphysis, junction of the manubrium and sternum,
intervertebral joints. Functionally, this is an amphiarthrosis,
a slightly movable joint.
These have a space called a synovial cavity between the
articulating bones. Classified functionally as diarthroses.
The bones at synovial joint are covered by an articular cartilage.
Consists of two layers, an outer fibrous capsule and an inner
Synovial membrane-areolar connective tissue with elastic fibers.
Adipose tissue-articular fat pads.
Synovial fluid: the synovial membrane secretes this. Consists of
hyaluronic acid and interstitial fluid filtered from blood plasma.
Reduces friction by lubricating the joint. Supplies nutrients and
removes metabolic wastes. Contains phagocytic cells. Benefits of
a “warm up” before exercise is that it stimulates the production and
secretion of synovial fluid.
Accessory ligaments and articular discs:
Nerve and Blood Supply: contain many nerve endings.
Convey information to the brain and spinal cord.
Arteries penetrate the ligaments and articular capsule to
deliver oxygen and nutrients. Veins remove carbon
dioxide and wastes from the joints. The articulating
portions receive nourishment from the fluid. Rest by
Types of Synovial Joints
Planar joints- the articulating surfaces are flat or slightly
curved. Example are intercarpal joints, intertarsal joints,
sternoclavicular joints, acromioclavicular joints,
sternocostal joints, vertebrocostal joints.
Hinge Joints-the convex surface of one fits into the
concave surface of another. Eg. Knee, elbow, ankle,
interphalangeal. Monaxial (uniaxial).
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. Examples atlanto-axial
joint, radioulnar joint:turns palm anteriorly and posteriorly.
Types of Synovial Joints
Condyloid Joints-also called ellipsoidal joint. The convex oval-
shaped projection of one fits into the oval-shaped depression of
another. Eg. Wrist and metacarpophalangeal joints. Biaxial.
Saddle Joints-here the articular surface of one bone is
saddle-shaped and the articular surface of the other fits
into the “saddle”. Eg. Carpometacarpal joint. Biaxial.
Ball-and-Socket Joints- this consists of the ball-like
surface of one bone fitting into a cuplike depression of
another bone. Egs. Shoulder and hip joints. Multiaxial.
Bursae and Tendon Sheaths
Bursae: saclike structures that reduce friction. Located
in the shoulder and knee joints. Found between skin
and bone, tendons and bones, muscles and bones,
ligaments and bones.
Tendon Sheaths: tubelike bursae that wrap around
tendons. Found at the wrist, ankle, fingers and toes.
Types of Movements
Gliding: this consists of side-to-side and back-and-
Angular movements: there is an increase or decrease
in the angle between articulating movements.
Includes flexion, extension, lateral flexion,
Abduction: this is the movement of a bone away from
Adduction: this is the movement of bone toward the
Circumduction: this is the movement of the distal
end of a body part in a circle
Types of Movements
Rotation: a bone revolves around its own longitudinal axis.
Pivot and ball-and-socket joints permit rotation. Medial
(internal) rotation and lateral (external) rotation.
Special movements: elevation, depression, protraction,
retraction, inversion, eversion, dorsiflexion, plantar flexion,
supination, pronation, opposition.
Factors affecting ROM at Synovial Joints
Structure or shape of the articulating bones
Strength and tension of ligaments.
Arrangement and tension of muscles
Apposition of soft parts
Range of motion (ROM)
Refers to the range, measured in degrees of a circle, through which the bones of a joint can
Aging and Joints
Decreased production of synovial fluid
Articular cartilage becomes thinner with age, ligaments
shortens and lose flexibility.
Males commonly develop degenerative changes in the
Osteoarthritis-occurs over age 70.