Joint

A joint is a connection between two or more bones that allows movement.

There are three different types of joints:

Fibrous joint

In a fibrous joint, two bones are connected by connective tissue. These are found, among other places, between the tibia and the fibula.

Cartilaginous joint

A cartilaginous joint is held together by cartilage. An example is the connection between the sternum and the so-called xiphoid process at the bottom of the sternum.

Synovial joint

In a synovial joint, the bones are separated by a joint cavity filled with fluid. This cavity exists because the joint is surrounded by a joint capsule. Examples of synovial joints are:

• Knee
• Hip
• Elbow
• Etc.

Structure of a synovial joint

Synovial joints are the most common and most complex joints in the body. The fluid (synovia) in the joint cavity and the cartilage ensure smooth movements. A synovial joint always consists of a joint head and a joint socket that, to a greater or lesser extent, fit together.

The structure of this head and socket largely determines the stability of the joint. The head and socket are covered with cartilage. In addition to the structure of the head and socket, the joint is held together and stabilized by the joint capsule, ligaments, muscles, and tendons

A synovial joint can consist of two bones (= simple joint), multiple bones (= multiple joint), or bones and other structures such as a meniscus (= complex joint).

Different types of synovial joints

In addition, a synovial joint is divided into different types:

Hinge joint.
In a hinge joint there is one (één) direction of movement, as with a hinge. For example, as in the elbow joint.

Pivot joint.
In a pivot joint only one (één) movement is possible and that is rotation. For example, the joint between the radius and the ulna.

Saddle joint.
A saddle joint is named after the shape of the bones, which have a saddle shape. As in the transition from a metacarpal to a carpal bone. Movement in this joint is possible around two axes.

Ellipsoïd joint
An ellipsoid joint has the shape of an ellipse, as in the wrist joint. Just like in the saddle joint, movement is possible around two axes.

Ball-and-socket joint.
In a ball-and-socket joint, movement is possible around three axes, which also allows the joint to rotate around its own axis. For example, as in the shoulder and hip joints.