The capsule is “…continuous cylinder…” of fibrous tissue that surrounds the glenohumeral joint.  It is composed of two layers  and allows the biceps tendon to traverse it at the intertubercular groove and at the subscapularis bursa region. 
Moseley and Overgaard  classified capsular insertion into one of three types:
- Type 1 – capsular insertion on the labrum.
- Type 2 – capsular insertion at the junction of the labrum and the glenoid.
- Type 3 – capsular insertion more medial to the junction between the labrum and glenoid on the cortical surface of the glenoid neck.
Arthroscopically, the attachment of the anterior capsule to the humeral head is visible.  MR Imaging and MR Arthrographic studies have shown variation in its attachment, which have been classified according to the Moseley and Overgaard  system [Table 12]. [28,32]
The antero-inferior capsule is described as being “…smooth and covered with a thin synovial investment” when seen through an arthroscope. In a cadaveric study, Eberly et al  reported two types of capsular attachment to the glenoid. Type 1 origin occurred in 80% of cases and was characterised by the capsule mainly originating “…from the labrum, with some fibres extending onto the glenoid neck”.  Type 2 origin occurred in 20% of cases and involved the capsule originating from the glenoid neck only. 
Arthroscopically, the inferior capsular attachment to the humeral head is likened to a hammock. 
The posterior capsule is attached to the posterior labrum and appears fairly smooth “…except for the presence of a thickening, the posterior-superior band of the inferior capsular ligament”. 
Similar to the anterior capsule, MR Imaging and MR Arthrography studies have shown variation in the attachment of the posterior capsule [28,32].