There are actually four joints associated with the shoulder complex, not five, as detailed in the reference material. These joints work together to provide a wide range of motion to the arm and shoulder. Here is a breakdown of these four joints:
Understanding Shoulder Joints
The shoulder is a complex area, involving multiple bones and their articulations. It's important to understand that the shoulder girdle includes the clavicle and scapula, which then connect with the humerus of the upper arm.
Key Shoulder Joints
| Joint Name | Description |
|---|---|
| Sternoclavicular (SC) | This joint is where the clavicle (collarbone) meets the sternum (breastbone). It's the only bony attachment of the shoulder girdle to the axial skeleton. |
| Acromioclavicular (AC) | This joint connects the acromion (part of the scapula) to the clavicle. It allows for movements like shrugging and helps with overhead arm movement. |
| Scapulothoracic | This is technically not a true joint but rather a physiological articulation where the scapula glides against the rib cage (thorax). This "joint" facilitates a wide range of motion in the shoulder. |
| Glenohumeral | This is the main shoulder joint, where the head of the humerus fits into the glenoid fossa of the scapula. It is a ball and socket joint, offering great mobility. |
Function of the Shoulder Joints
- Sternoclavicular Joint (SC): Provides stability and allows movement like elevation, depression, protraction, and retraction of the shoulder girdle.
- Acromioclavicular Joint (AC): Allows for further movement and adjustments of the scapula in relation to the clavicle.
- Scapulothoracic Joint: Essential for the scapula's movements including rotation, which adds to overall arm range.
- Glenohumeral Joint: The main joint providing arm rotation, abduction (raising the arm away from the body), and adduction (moving the arm towards the body).
It is important to note that the shoulder complex functions as a coordinated unit. While each joint has specific roles, they all contribute to the overall mobility and function of the shoulder and arm.
