Articulations ~ Joints
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nts/landing.html
Definition
Bones can move because of the way they
are joined together. The place where two
or more bones come together is called a
joint. The bones at a joint are held
together by strong bands of tissue called
ligaments which allow the bones to move.
However, there are several different kinds
of joint, and each one moves differently.
Types of Joints
Fibrous joints connect bones without allowing any
movement. The bones of your skull and pelvis are
held together by fibrous joints. The union of the
spinous processes and vertebrae are fibrous joints.
Cartilaginous joints are joints in which the bones are
attached by cartilage. These joints allow for only a
little movement, such as in the spine or ribs.
Synovial joints allow for much more movement than
cartilaginous joints. Cavities between bones in
synovial joints are filled with synovial fluid. This fluid
helps lubricate and protect the bones. Bursa sacks
contain* the synovial fluid.
Ball and Socket
The ball-and-socket joint is found in the
hip-bone and the shoulder and allows the
most movement of all the joints. One bone
has a ball-like knob at the end of it, and
the knob fits into a cup-like space on the
other side. The ball-and-socket joint is
what allows baseball pitchers to throw a
ball with such tremendous speed.
Gliding movements
Intercarpal joints
Sliding ~Gliding
The sliding joint is found in the vertebral
column and allows small sliding
movements. The vertebrae have pads of
cartilage between them, and the bones
slide over these pads. This is what makes
the backbone so flexible.
Pivot
The pivot joint allows movement turning
from side to side, and your head is
attached to your vertebral column with this
joint. A hole in one bone fits over a pointed
part of the other bone, so that one bone
can turn on top of the other.
Pivot
Rotation of one bone
around another
Atlas and Axis
Hinge
The hinge joint allows bones to move
back and forth, and is found in your elbow
and knee. It allows bones to move like a
hinge in a door.
Condyloid - Similar to the ball and socket joint, the
condyloid joint allows circular motion. In the condyloid
joint, the ball rests up against the end of a bone rather
than inside a socket. Example: The carpals of the
WRIST rest against the end of the RADIUS bone of the
forearm.
Saddle - The saddle joint allows movement in various
directions. For example, where the THUMB meets the
wrist the bones fit up against each other like a saddle fits
over the back of a horse.
It might seem funny, but there is one type
of joint which doesn't allow any movement
at all. A joint between bones that do not
move at all is called a fixed joint, and one
place the fixed joint is found is in your
skull. When babies are born, their skull
bones are not joined together yet. In fact,
there is a gap between them called the
fontanel, or soft spot. However, the bones
quickly grow together to protect the brain.
Review 1
1. fixed joint
2. pivot joint
3. ball-and-socket joint
4. sliding joint
5. hinge joint
A painful sacroiliac joint is
one of the more common
causes of mechanical low
back pain. Sacroiliac (SI)
joint dysfunction is a term
that is used to describe the
condition - because it is still
unclear why this joint
becomes painful and leads
to low back pain. Sacroiliac
joint dysfunction can be a
nuisance but it is seldom
dangerous and rarely leads
to the need for surgery.
Review 2
Ball and Socket
Condyloid
Hinge
Pivot
Saddle