Did you know we have different types of joints in our body? Each joint has a specific name and function. In this article, we’ll explore the different types of joints, what they do, where they are and give examples of each one.
- What is a joint?
- Classification of joints
- Types of synovial joints
- Fibrous / synarthrosis joints
- Amphiarthrosis / cartilaginous joints
What is a joint?
A joint is a point of connection between two or more bones in the body, which is also called an articulation. Joints provide structural support and allow movement.
What are the classification of joints?
Joints can be classified by (1) the amount of movement they allow and/or (2) the type of tissue that connects the bones together. The two classification systems correlate, and there are three main types of joints based on these classification systems:
|Name Classified by Amount of Movement||Name Classified by Type of Tissue|
|Diarthroses (freely moveable)||Synovial|
|Amphiarthrosis (slightly moveable)||Cartilaginous|
Diarthrosis / Synovial Joints
Synovial joints, also called diarthrosis joints, is a type of joint that freely allows smooth movement between the connecting bones. This influences our movement and ability to perform skills in sport.
Synovial joints have several key structures, which help to prevent injury. These structures include:
The synovial membrane is a thin layer of tissue that lines the inner surface of the joint capsule and produces synovial fluid.
Synovial fluid is a thick liquid between your joints that acts as a lubricant, helping to reduce friction and wear within the joint.
The joint capsule surrounds the synovial joints, it protects the synovial membrane.
Bursae are small fluid-filled sacs that provide cushion between bones, tendons and/or muscles around a joint. It helps to reduce friction between bones while allowing free movement of joints.
Cartilage is a thin layer of smooth, elastic tissue that covers the surface of the end of bones within the joint. It helps to reduce friction and wear as the bones move against each other.
Ligaments are strong bands of connective tissue that help to hold the bones of the joint together and provide stability.
Tendons are strong, flexible bands of connective tissue that attach muscle to bone. They help to move the bones of the bones of the joint by pulling on the tendons.
Types of Synovial Joints
Synovial joints are subdivided into six types, which are based on the movements possible. The six types of synovial joints are hinge, pivot, ball & socket, ellipsoid, saddle and plane.
A hinge joint is a uniaxial joint, it allows for bending (flexion) and straightening (extension) in one direction (axis) only. In other words, it’s like a door, which opens and closes in one direction.
Example of hinge joint
An example of a hinge joint is the elbow joint where the humorous (upper arm joint), ulna and radius (forearm bones) are connected. Hinge joints are also found at the knee, ankle, finger and toe (interphalangeal) joints.
A sporting example of a hinge joint is the movement at the elbow joint when making a basketball shot. The elbow joint starts in a flexed position and as you shoot, the arm straightens which creates extension at the elbow joint in the sagittal plane.
Another example of a hinge joint is at the knee (made up of the femur, tibia and fibula bones) joint when preparing to kick a football. The knee starts in a relatively straight position (extension) and when you prepare to kick the ball, you bend the leg at the knee joint (flexion), which decreases the angle at the joint.
Fun fact: The knee joint also contains a small amount of rotation (2-5º), which just shows there are variances even within joint types.
A pivot joint is a uniaxial joint, it allows for rotation around one axis.
Example of a pivot joint
An example of a pivot joint include the atlantoaxial joint, which is formed between the atlas (first vertebrae) and axis (second vertebrae) bones, directly under the skull. This joint allows us to turn our head from side to side, as if we were shaking our heads to say no or looking sideways for where our opposition is on the field of play.
Another example of a pivot joint is the radioulnar joint, which is made up of the radius and ulna in the forearm. It is responsible for turning the palm upwards (supernation) and downwards (pronation) in the transverse plane, which helps us to rotate the forearm when turning keys in locks.
The radioulnar joint plays a key role in generating power in striking action, such as the golf swing and tennis serve.
Condyloid (Ellipsoidal) Joint
A condyloid joint, also known as an ellipsoidal joint is a biaxial joint, which is formed by a shallow depression at one end of a bone that joins a rounded structure of the other bone.
Example of Condyloid joint
One example of a condyloid joint is the knuckle (metacarpophalangeal) joints in the hand. This allows us to spread our fingers apart (abduction) and together (adduction) in the frontal plane as well as bending (flexion) and straightening (extension) the fingers in the sagittal plane.
As you may gather from the description above, these joints are complex. Consider where the muscles reside to abduct and adduct your fingers (spread out within your hand). Such joints offer many degrees of freedom and allow us to hold, manipulate and throw objects such as clubs, rackets and balls.
A saddle joint is a biaxial joint, it is categorised by the shape of the joining bones, which are concave in one direction and convex in the other so that the two bones fit together, much like a saddle sits on a horse’s back. This allows for bending (flexion) and straightening (extension) in the sagittal plane and movements side to side (abduction and adduction) in the frontal plane.
Example of Condyloid joint
An example of a saddle joint is at the base of the thumb (carpometacarpal joint), which is formed by the carpal bone (trapezium) and first finger bone (metacarpal). It allows for precise movements and for providing stability to the hand.
You may have just noticed that you can’t rotate your thumb…tried it?
Ball & Socket Joint
A ball and socket joint is a multiaxial joint and the most freely movable synovial joint. It is formed when the round head of a bone (referred to as the ball) fits into a concave space (referred to as the socket) of the connecting bone, a bit like a golf ball on a tee.
There are only two ball and socket joints, which are the shoulder (glenohumeral) and hip (acetabulofemoral) joints.
The hip joint is formed by the femur and pelvis, where the head of the femur (femoral head) is the “ball” which fits into the socket, inside the pelvis (acetabulum). The hip joint is one of the most stable joints, because of the depth of the socket.
The shoulder joint is formed by the humerus and scapula, where the head of the humerus (the ball) fits into the scapula in the glenoid cavity (the socket). The shoulder is less stable than the hip joint, as the socket is shallow and smaller than the ball.
A ball and socket joint allows for a wide range of movement, including flexion and extension in the sagittal plane, abduction and adduction in the frontal plane and internal and external rotation in the transverse plane.
A plane joint, also known as a gliding joint, is a multiaxial joint. It is formed when the two joining bones which are relatively parallel to one another are relatively flat. They allow for short gliding or sliding movements between the bones in no defined plane.
Examples of plane joints are between the carpal bones (intercarpal joints) of the wrist, the tarsal bones (intersal joints) of the foot and between the clavicle and chromium of the scapula (acromioclavicular joint).
Plane joints are very challenging to model in sport science, as there is no clear joint centre.
Fibrous / Synarthrosis Joints
Fibrous joints, also called synarthrosis joints, this is a joint that has no movement and is connected by fibrous connective tissue. It provides a strong connection between two bones, which is important for protection.
Three examples of fibrous joints are:
Sutures are the joints in the skull, which provides protection for the brain. During birth and in young babies, these joints are still forming and have some flexibility, before they solidify to create the fixed shape of our skull and offer great protection to our brain.
Gomphoses is the joint that anchors teeth into their sockets in the jaw of the skull.
A syndesmosis joint attaches two bones that are parallel to each other together by a sheet of fibrous connective tissue called an interosseous membrane.
One example of this is in the forearm, where an interosseous membrane is between the radius and ulna, which connects them together.
Amphiarthrosis / Cartilaginous Joints
Amphiarthrosis joints, also called cartilaginous joints, these are joints that have some movement and are connected by either hyaline cartilage or fibrocartilage.
There are two types of amphiarthrosis / cartilaginous joints:
Synchondroses / Primary Cartilaginous Joints
A synchondrosis joint joins bones together by hyaline cartilage or where the bone is connected to hyaline cartilage and can be temporary or permanent.
An example of a temporary synchondrosis joint is an epiphyseal plate of a growing long bone. It is lost when the epiphyseal plate ossifies, which happens when the bone reaches maturity. When the synchondrosis joint is lost, it is replaced by a synostosis joint.
An example of a permanent synchondrosis joint is the sternocostal joint, which is where the first rib connects to the sternum via hyaline cartilage.
Symphysis / Secondary Cartilaginous Joints
A symphysis joint joins bones together by either hyaline cartilage or fibrocartilage.
An example of a symphysis joint is the pubic symphysis, which consists of a fibrocartilaginous disk in between hyaline cartilage on the ends of both pubic bones.
In sport, it’s important that we understand the fundamentals of the human skeleton. We’ve covered the three main types of joints – fibrous, cartilaginous and synovial, which all allow a different level of movement and are connected by a different type of connective tissue.
Next time you’re looking at sporting movements, see if you can identify which type of joint is present and what movement it allows.
To learn more about the human skeleton and how it works, check out our other articles here.
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