The shoulder joint is a ball-and-socket synovial joint.
This type of joint allows for a wide range of motion, making it the most mobile joint in the human body. The "ball" is the head of the humerus (upper arm bone), and the "socket" is the glenoid fossa, a shallow depression in the scapula (shoulder blade).
Here's a breakdown of what makes it a ball-and-socket joint:
- Ball: The spherical head of the humerus fits into the socket.
- Socket: The glenoid fossa of the scapula forms the socket.
- Synovial: The joint is enclosed in a capsule containing synovial fluid, which lubricates the joint and reduces friction during movement.
- Movement: This arrangement permits movement in multiple planes, including flexion, extension, abduction, adduction, circumduction, and rotation.
The shoulder's extensive mobility also makes it relatively unstable compared to other joints. Structures like the rotator cuff muscles, tendons of the biceps and triceps brachii, and ligaments provide stability and help control movement.
