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Joints
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Joints Overview
• A joint, otherwise known as an articulation, is a point at which
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points connect.
They are constructed to allow movement (except for skull
bones) and provide mechanical support.
There are three ways to classify joints, their structural,
functional, and biomechanical properties.
To classify a joint as structural, it can be a fibrous joint, a
cartilaginous joint, and a synovial joint.
To classify a joint as functional, it can be either synarthrosis,
amphiarthrosis, or diarthrosis.
To classify a joint as biomechanical, it can be a simple,
Structure and Function of Joints
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A Fibrous Joint is a joint joined by dense regular
connective tissue that is rich in collagen fibers.
o Most fibrous joints are synarthrosis. They are
“fixed” or immovable.
A Cartilaginous Joint is a joint that is connected
together by cartilage.
o Most cartilaginous joints are amphiarthrosis.
They permit slight mobility.
● A Synovial Joint is a joint that is not directly joined.
The bones have a synovial cavity and are united by
the dense irregular connective tissue that forms the
joint capsule that is normally associated with
accessory ligaments.
○ All synovial joints are diarthrosis. They are
Biomechanical Classification of
Joints
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Biomechanical classification is broken up into simple, compound, and
complex joints depending on the number of bones and other surfaces
involved.
Simple Joint - A simple joint is a joint that includes two bones.
o Examples: Shoulder and Hip joint
● Compound Joint - A compound joint is a joint that includes three bones.
○ Examples: Wrist Joints
● Complex Joint - A complex joint is a joint that includes two bones and a
disc or meniscus.
○ Examples: Knee Joint
Types of Joints
❖Ball & Socket
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Shoulder
Hips
❖Gliding
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Ankle
Wrist
❖Hinge
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Elbow
Ball & Socket
❖ Have the most range of movement
❖ In the shoulder joint, the humerus (upper arm bone)
fits into the socket of the shoulder blade.
❖ Because the socket is shallow and the joint loose, the
shoulder is the body's most mobile joint
❖ Hip joint is less mobile than the shoulder, but more
stable
❖ Ball of the femur's head fits tightly into a deep socket
in the hip bone
Hip Joint
❖ One of the most important joints in the human body
❖ A round, cup-shaped structure between the hip bone,
called the acetabulum, forms the socket for the hip joint
while he rounded head of the femur forms the ball of the
joint
❖ Allows us to walk, run, and jump
❖ It also bears our body’s weight and the force of the strong
muscles of the hip and leg
❖ However, the hip joint is also one of our most flexible joints
and allows a greater range of motion than all other joints in
Gliding Joint
❖ Connects to a flat bony surface
❖ Has three types of range of motion (Linear motion,
circular motion, and gliding motion)
❖ Permits a wide range of mostly sideways movements
as well as movements in one direction
❖ Pivot joint near the top of the spine allows the head to
swivel and bend
❖ Other pivot joints in the forearm and lower leg allow
the wrist and ankle to twist
Ankle Joint
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It is a hinge joint with primarily up and down movement
The bones that compose this joint are the tibia, fibula and talus
The subtalar joint sits below the ankle joint, and allows side-to-side
motion of the foot
Wrist Joint
● It is a complex joint that bridges the hand to the forearm
● The bones comprising the wrist include the distal ends of the radius
and ulna, 8 carpal bones, and the proximal portions of the 5
metacarpal bones
● Due to this joint the hand is capable of 3 degrees of freedom;
flexing and extending, pronating and supinating, and deviating
ulnarly or radially.
Hinge Joint
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They allow movement in only one direction
Some examples of hinge joints are the elbow, which
joins the humerus with the ulna, and the knee, which
joins the femur with the tibia.
Like a door, these joints can move back and forth, but
cannot swivel or move in any other directions.
The hinge joint of the knee, the body's largest joint, is
unusual because it can swivel on its axis, allowing the
foot to turn from side to side. Thus, the knee is
constantly rolling and gliding during walking.
Elbow Joint
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The elbow joint is a complex hinge joint formed between
the distal end of the humerus in the upper arm and the
proximal ends of the ulna and radius in the forearm.
The elbow allows for the flexion and extension of the
forearm relative to the upper arm, as well as rotation of
the forearm and wrist.
The rounded distal end of the humerus is divided into
two joint processes – the trochlea on the medial side
and the capitulum on the lateral side. The pulley-shaped
trochlea forms a tight joint with the trochlear notch of the