Joints (articulations)
 Hold bones together securely.
 Give the rigid skeleton mobility.
 Classified in 2 ways:
o Functionally – focuses on the amount of movement
allowed.
 Synarthroses = immovable joint.
 Amphiarthroses = slightly movable joint.
 Both of the above joint types are restricted
mainly to the axial skeleton where firm
attachments & protection of internal organs
are priorities.
 Diarthroses = freely movable joints.
 Predominate in the limbs, where mobility is
important.
o Structurally – based on whether fibrous tissue,
cartilage or a joint cavity separates the bony regions.
 General rule:
 Fibrous = immovable.
 Synovial = freely movable.
 Cartilaginous = both immovable & slightly
movable examples, but most are
amphiarthrotic.
Fibrous Joints
 Bones are united by fibrous tissue.
 Sutures – irregular edges of bone interlock, bound tightly
by connective tissue fibers = essentially no movement.
 Syndesmoses – connecting fibers are longer & have more
give. Ex: joint connecting distal ends of tibia & fibula.
Cartilaginous Joints
 Bone ends connected by cartilage.
 Examples:
o Slightly movable (amphiarthrotic) = pubic symphysis
& intervertebral joints of the spine.
o Immovable (synarthrotic) = hyaline-cartilage
epiphyseal plates of growing long bones & the
cartilaginous joints between the 1st ribs & the sternum.
Synovial Joints
 The articulating bone ends are separated by a joint cavity
containing synovial fluid = all joints of the limbs.
 4 distinguishing features:
o Articular (hyaline) cartilage covers the ends of the
bones forming the joint.
o Fibrous articular capsule encloses the joint surfaces
& the capsule is lined w/ a smooth synovial
membrane.
o Joint cavity enclosed w/ in the capsule contains
lubricating fluid.
o Reinforcing ligaments surround the capsule.
 Bursae & tendon sheaths are not part of synovial joints, but
are closely associated w/ them – act like ball bearings to
reduce friction.
o Bursae – flattened fibrous sacs lined w/ synovial fluid
– common where ligaments, muscles, skin, tendons or
bones rub together.
o Tendon sheath – an elongated bursa that wraps
completely around a tendon subjected to friction.
Synovial Joint:
Types of Synovial Joints Based on Shape
The shapes of the articulating bone surfaces determine the
movement of a joint.
 Plane joint
o Articular surfaces are essentially flat & only short,
gliding movements are allowed.
o Nonaxial = no rotation.
o Ex: intercarpal joints of wrist.
 Hinge joint
o Cylindrical end of 1 bone fits into a trough-shaped
surface of another bone.
o Angular movement in one plane.
o Uniaxial = allow movement around one axis only.
o Ex: elbow, ankle, & joints between phalanges.
 Pivot joint
o Rounded end of 1 bone fits into a sleeve of ring of
bone (& possibly ligaments).
o Uniaxial – can only turn around its long axis.
o Ex: proximal radioulnar joint & joint between the atlas
& the dens of the axis.
 Condyloid joint/ A.K.A Ellipsoid joint(knuckle-like)
o Egg-shaped articular surface of 1 bone fits into the
oval concavity of another.
o Both surfaces are oval.
o Allows the moving bone to travel from side to side &
back and forth, but can’t rotate around its long axis.
o Biaxial (mov’t around 2 axes)
o Ex: metacarpophalangeal joints (knuckles).
 Saddle joint
o Each articular surface has both convex & concave
areas, like a saddle
o Biaxial like the condyloid joints
o Ex: carpometacarpal joints in the thumb (twiddling!)
 Ball & Socket joint
o Spherical head of one bone fits into round socket in
another
o Multiaxial joint (mov’t in all axes including rotation)
o The most freely moving synovial joint
o Ex: shoulder & hip