During protraction and retraction of the SC joint, the clavicle rotates about its long axis.
True
False
The correct answer and explanation is:
Correct Answer: ✔️ False
Explanation:
During protraction and retraction of the sternoclavicular (SC) joint, the clavicle does not rotate about its long axis. Instead, it glides anteriorly and posteriorly relative to the sternum in the transverse plane.
Let’s break it down:
Understanding the SC Joint Movements:
The SC joint is a saddle-type synovial joint that connects the clavicle (collarbone) to the sternum (breastbone). It is the only true joint that connects the upper limb to the axial skeleton and is highly mobile due to its structure.
The movements at the SC joint include:
- Elevation and Depression – movement in the frontal plane.
- Protraction and Retraction – movement in the transverse (horizontal) plane.
- Axial (longitudinal) Rotation – occurs during arm elevation, not during protraction or retraction.
Protraction and Retraction Explained:
- Protraction: The clavicle moves anteriorly, bringing the shoulder forward.
- Retraction: The clavicle moves posteriorly, pulling the shoulder backward.
These movements involve anterior and posterior gliding of the clavicle at the SC joint. The movement occurs at the articular surfaces, but the clavicle does not rotate around its long axis during these motions.
When Does the Clavicle Rotate Around Its Long Axis?
The clavicle rotates about its longitudinal axis during arm elevation (flexion or abduction above 90 degrees). This axial rotation allows the acromioclavicular joint to maintain the scapula’s alignment with the thoracic cage.
Conclusion:
Therefore, it is false to say that the clavicle rotates about its long axis during protraction and retraction. Those motions involve translational (gliding) movements, not rotational ones.