Joint Structure
Classification of Joints

Fibrous (synarthroses): lacks a joint
cavity and the articulating bones are held
very closely together by fibrous connective
tissue; they permit little or no movement
– sutures
– syndesmoses
– gomphoses
Sutures

found between the
bones of the skull and
are united by a thin
layer of dense fibrous
connective tissue
Syndesmoses

fibrous connective
tissue forms an
interosseous
membrane or ligament
(distal articulation of
the tibia and fibula,
shafts of radius and
ulna)
Gomphoses

cone-shaped peg fits
into a socket (teeth)
Classification of Joints
 Cartilaginous
(amphiarthroses):
lacks a joint cavity and the articulating
bones are tightly connected by
cartilage
– synchrondrosis
– symphyses
Synchrondrosis

connecting material is
hyaline cartilage
(epiphyseal plate)
Symphyses

connecting material is
a broad, flat disc of
fibrocartilage (pubic
symphysis; bodies of
vertebrae)
Classification of Joints
• Synovial (diarthroses): joint cavity
(space between the articulating bones)
is present; freely movable.
– Gliding
– Hinge
– Pivot
– Ellipsoidal
– Saddle
– Ball and socket
Synovial
Joints are
freely
movable
Gliding
• side-to-side and back-and-forth
movements (biaxial); articulating surfaces
are usually flat (intercarpal, intertarsal,
sternum and clavicle)
Synovial Joints
Hinge
• motions are flexion/extension (monoaxial);
convex surface of one bone fits into the
concave surface of another (elbow, knee)
Synovial Joints
Pivot
• rotational movement (monoaxial);
rounded, pointed, or concave surface fits
into a ring formed partly by bone and
partly by a ligament (atlas and axis)
Synovial Joints
Ellipsoidal
• side-to-side and back-and-forth
movements (biaxial); oval shaped condyle
fits into an elliptical cavity (wrist)
Synovial Joints
Saddle
• side-to-side and back-and-forth
movements (biaxial); articular surfaces
concave in one direction and convex in
opposite direction (CMC of thumb)
Synovial Joints
Ball and socket
• movement in 3 planes (triaxial); ball like
surface fits into a cuplike depression
(shoulder and hip)
Synovial Joints
Components of Synovial Joints
• articular cartilage: covers surfaces of
articulating bones but does not bind them
together
• articular capsule: surrounds the articular
surfaces and encloses the joint cavity
– outer layer (fibrous capsule): attached to the
periosteum of articulating bones at a variable distance
from the edge of the articulating cartilage
– inner layer (synovial membrane): secretes synovial
fluid which lubricates the joint
and provides
nourishment for the articular cartilage
Components of Synovial Joints
• joint (synovial) cavity: enclosed space that
surrounds the 2 articulating surfaces; contains
the slippery lubricating fluid called synovial fluid
• ligaments: thickened collagenous bands
connecting bone to bone
– extracapsular ligaments are outside of the articular
capsule (MCL, LCL)
– intracapsular ligaments directly attach the 2
articulating surfaces (ACL, PCL)
Components of Synovial Joints
• articular discs (menisci): pads of
fibrocartilage that lie between the articular
surfaces of the bones; help maintain the
stability of a joint and direct the flow of
synovial fluid to areas of greatest friction;
not all synovial joints have them
Components of Synovial Joints
• bursae: saclike structures that contain
synovial fluid to help reduce friction
between:
– skin and bone
– tendons and bones
– muscles and bones
– ligaments and bones