: The labrum broadens and makes deeper the glenoid socket (top image). The labrum also acts as an anchoring point for the ligaments of the shoulder (lower image).
The normal main ligament of the shoulder (inferior glenohumeral ligament) supports the humeral head like a hammock supports a person (top image). With arm rotation, the ligament (hammock) moves forward and backward to keep the ball in the socket during this rotation (lower image).
Arm elevation Flexion Abduction Flexion and abduction Extension
Horizontal plane 30-45° ° 15-30° 90°
Flexion and extension in horizontal plane extension flexion