JOINTS
The
Facts Put Simply
.
A Primer On
Joints
Generally;
Joints are an important piece of the Arthritis puzzle as Arthritis
usually affects the joints of the body. The three most commonly
affected joints are the Knee, Shoulder and Hip joints.
A joint is the point at which two bones come together. Most
joints are mobile (articulating) which allows the bones to move.
A joint may consist of the following components:
• Cartilage
- at the joint, the bones are covered
with cartilage (a connective tissue), which is made up of cells and
fibers and is wear-resistant. Cartilage helps reduce the friction of
movement.
• Synovial membrane - a tissue called the synovial
membrane lines the joint and seals it into a joint capsule. The
synovial membrane secretes synovial fluid (a clear, sticky fluid)
around the joint to lubricate it.
• Ligaments - strong ligaments (tough, elastic
bands of connective tissue) surround the joint to give support and
limit the joint's movement.
• Tendons - tendons (another type of tough
connective tissue) on each side of a joint attach to muscles that
control movement of the joint.
• Bursas - fluid-filled sacs, called bursas,
between bones, ligaments, or other adjacent structures help cushion the
friction in a joint.
• Synovial fluid - a clear, sticky fluid secreted
by the synovial membrane.
• Femur - the thigh bone
• Tibia - the shin bone
• Patella - the knee-cap
• Meniscus - a curved part of cartilage in the
knees and other joints
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| Example of the Knee joint
|
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| Example of the Shoulder joint
|
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| What are the different types
of joints?
|
There
are many different types of joints and they are
classified according to structure and to how they move.
Joints that do not move are called "fixed."
Other joints may move a little, such as the vertebrae. Examples of
mobile joints include:
• ball-and-socket joints, such
as the shoulder and hip joints - allow
backward, forward, sideways, and rotating movements
• hinge joints, such as in the fingers, knees, elbows, and toes - allow
only bending and straightening movements
• pivot joints, such as the neck joint - allows limited rotating
movements
• ellipsoidal joints, such as the wrist joint - allow all types of
movement except pivotal movements
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