The rotation of the arm at the shoulder joint involves both internal and external rotation, each with its own range of motion and muscle groups.
Internal Rotation
Internal rotation at the shoulder joint is the movement of the arm towards the midline of the body, along a vertical axis.
- Normal Range of Motion: The normal range for internal rotation is 70 to 90 degrees.
- Muscles Involved: Several muscles facilitate internal rotation:
- Subscapularis
- Pectoralis Major
- Latissimus Dorsi
- Teres Major
- Anterior Aspect of the Deltoid
External Rotation
External rotation at the shoulder joint is the movement of the arm away from the midline of the body, along a vertical axis.
- Normal Range of Motion: The normal range for external rotation is 90 degrees.
Summary of Shoulder Rotation Ranges
| Type of Rotation | Normal Range of Motion |
|---|---|
| Internal Rotation | 70 to 90 degrees |
| External Rotation | 90 degrees |
In summary, the shoulder joint has a substantial range of rotation in both internal and external directions. Internal rotation can achieve 70-90 degrees of movement, while external rotation can achieve around 90 degrees. Understanding these ranges and the related muscle groups is crucial for both athletic performance and the rehabilitation of shoulder injuries.
