>> Welcome to the second course of our Sports Anatomy Series, Joints.
If you haven't complete our course about bones yet, we recommend that you do
that before beginning this course.
Joints are structures found throughout the body where two bones connect.
There are three different types of joints found in the body.
Fibrous joints allow the least amount of movement.
The joints in our skull are fibrous joints that give the skull strength to protect the brain.
Cartilaginous joints allow a small amount of movement
and are found in the spine and rib cage.
Synovial joints allow a lot of movement and are going
to be the focus of the rest of this course.
Synovial joints are typically found in the arms and legs and allow the body to move
in many different ways during activities like running, jumping, or throwing.
The hip, knee, shoulder, and elbow are all common examples of synovial joints.
While these joints may seem simple from the outside, they're actually quite complex inside.
There are three major parts of synovial joints.
The first part are ligaments.
Ligaments are tough but flexible bands of tissue that connect the bones to one another.
In the picture to the left, the ligaments of the knee joint are highlighted in blue.
Ligaments provide stability to joints by helping to hold bones together and prevent the joints
from moving into positions that may cause injury or instability.
While ligaments are quite strong, they can tear if they are stretched too far.
The anterior cruciate ligament, or ACL, is one of the most commonly injured ligaments.
The ACL is now highlighted in red in the picture on the left.
The ACL connects the thigh bone, or femur, to the shinbone, or tibia.
It limits how much the knee joint can move into dangerous positions.
Cartilage is another important part of synovial joints.
There's a some type of cartilage called hyaline cartilage that covers the end of each bone.
You can see this hyaline cartilage in blue in the picture on the left.
This is one of the smoothest surfaces in the body and it allows the bones to move
against each other with almost no friction.
Fibrous cartilage serves as a shock absorber helping to protect the bones from damage.
It is a very strong tissue that is found where ligaments connect to bones
and sometimes between the ends of bones.
Now you can see the fibrous cartilage of the knee in blue in the picture on the left.
This fibrous cartilage is called the meniscus.
Like the meniscus some fibrous cartilage adds shape to the end of bones
and allows them to fit together better.
Cartilage in synovial joints is lubricated by a fluid called synovial fluid, which is the third
and final part of synovial joints.
Synovial fluid keeps the surfaces of the joints slippery
so there is minimal friction between the bones.
This helps to keep the bones from grinding against one another and causing pain or damage.
There are many types of synovial joints.
Two of the most commonly known are ball and socket, and hinge joints.
Let's get a better idea of how each type of these joints works.
The hip and shoulder are examples of ball and socket joints.
In these joints one bone has a rounded end and fits into a cup shaped socket on the other bone.
Notice how the shape of this joint allows the arm or leg to move around in many directions.
Try moving your arm or leg in a circle to see how this type
of joint gives your shoulders and hips mobility.
The elbow and knee are examples of hinge joints.
In this type of joint, one bone has rounded edges that fit nicely
in the concave edge of the other bone.
The shape of the bones only allows the joint to move easily in one direction.
Try bending and straightening your elbow, knee, or fingers to see a hinge joint at work.
Now that you've finished this course, complete the quiz on the next page to earn a certificate.
Check out more of our courses at sports-safety-hss.edu.