Joint Structure and Function

Header: Types of Joints

**Synovial joints** are the most common and freely movable type of joint in the body.
They include six sub-types: ball-and-socket, hinge, pivot, condyloid, saddle, and plane joints.
**Ball-and-socket joints**, such as the hip and shoulder joints, allow movement in all directions.
**Hinge joints**, like the elbow and knee, permit movement in one direction.
Pivot joints, found in the neck, allow rotational movement.
**Condyloid joints**, such as the wrist joint, allow movement in two planes.
**Saddle joints**, found in the thumb, allow movement similar to both the condyloid and hinge joint.
**Plane joints**, which include the ankle and wrist joints, allow gliding movements.

Header: Structural Components of Synovial Joints

Synovial joints have a synovial cavity that is filled with synovial fluid for lubrication.
The bones that meet at the joint are covered by a layer of smooth articular cartilage which reduces friction and absorbs shock.
**Synovial membrane** lines the joint capsule and secrets synovial fluid.
**Ligaments** connect bone to bone for stability and limit the joint’s motion.
**Tendons** connect muscle to bone and aid in joint movement.
Some joints also contain bursae, small fluid-filled sacs that reduce friction between tendons and bone.

Header: Joint Function

The primary function of joints is to provide mobility and flexibility to the body.
They also provide structural stability, securing the bones in position and distributing forces during movement.
Joints enable a wide range of motion, including bending, straightening, rotating and gliding movements.
The type and range of movements are determined by the structure of the individual joint.