CSEC PE Lecture: The skeletal system – types of synovial joints

Synovial joints have different structures, depending on how they work. They allow different kinds of movement depending on the shape of the bones at the joint and the ligaments that hold them together.

The shoulder, hip and ankle are very susceptible to injury because of the amount of movement possible at these joints. Sudden impact or over extension, etc., could cause dislocation or the tearing of tendons and ligaments. Joints are placed into groups based on their structures.

There are six (6) basic types of synovial joints:

- Ball and socket:- This is the most movable joint in the body. One bone has a bulge like a ball at the end that fits into a socket in the other bone. It can turn in many directions. Ligaments are often used to keep the joint stable. Examples of this type of joint are the shoulder and hip joints.

- Hinge:- These types of joint works like a hinge on a door. It moves in one plane only and will open until it is straight and no further. The movement is limited because of the shape of the bones and the position of the ligaments. Examples of this type of joint are the elbow and knee joints.

- Pivot:- This joint has a ring on a peg structure. One bone has a bit that juts out, like a peg or a ridge. This fits into a ring or notch on the other bone. Only rotation is possible at this joint. An example of this type of joint is between the atlas and the axis vertebrae in the neck.

- Saddle:- This type of joint allows movement in two planes at right angles to each other. Bones are shaped like saddles and fit neatly together. Movement allowed is side to side and back and forward. Movement is limited because of the shape of the bones. Example of this joint is at the thumb.

-Condyloid:- This type of joint allows movement in two planes. The rounded end of one bone fits into the hollow of another. Movements are back and forward and side to side. Ligaments prevent rotation. Example of this type of joint is the wrist.

- Gliding:- Here the ends of the bones are flat enough to glide over each other. There is little movement in all directions, which is limited by the ligaments. Of all the synovial joints, this one allows the least movement. Examples of this type of joint are located between the carpals bones of the hand, the tarsals of the foot and vertebrae.

Our joints and sport

Our different joints work smoothly together when we make skilled sporting movements. They are capable of a full range of movement in order to work well. The muscle and ligament surrounding each joint must be strong enough to give stability to the joint.

The demands of sport put severe stress on the joint; therefore, we must warm up thoroughly before activity and should warm down afterwards.

Joints can be injured as a result of impact, internal forces or a mixture of both. Common examples include sprained ankle, torn knee ligament and dislocated shoulders.

Types of joint and movements allowed

Ball and socketflexion and extension, abduction and adduction. Rotation and circumduction

Hinge - flexion and extension

Pivot - rotation only

Saddle - flexion and extension, abduction and adduction

Condyloid - flexion and extension, abduction and adduction

Gliding - some gliding in all directions

 

Cartilage, ligaments and tendons

 

Cartilage protects bones and stops them from knocking together. It forms a gristly cushion between the bones at slightly movable joints. It forms a smooth, slippery coat on the ends of bones at synovial joints.

Ligaments are the strong cords and straps that lash bones together and hold a joint in place. They are a bit elastic, enough to let the bones move.

Tendons are the cords and straps that connect muscle to bone. The best known tendon joins our calf muscle to our heel and is called the Achilles tendon.