Permanent functional lengthening of the anterior capsule leads to instability.
Types of capsular attachment:
Type 1: anterior capsule (MGHL) inserts into labrum
Type 2: anterior capsule inserts within 1 cm of labrum
Type 3: anterior capsule inserts more than 1 cm from labrum
Type of capsular attachment has no role in prediction of shoulder instability
Neutral/ internal rotation position: capsule is lax
ABER: Capsule tightens
Best measured on oblique sagittal sequences from the glenoid centre.
No significant difference in two positions, i.e, loss of capsular tightening, indicates lax capsule
1. Ng AWH et al. Assessment of capsular laxity in patients with recurrent anterior shoulder dislocation using MRI. AJR 2009: 192: 1690-1695
2. Palmer WE et al. Anterior shoulder instability: diagnostic criteria determined from prospective analysis of 121 MR arthrograms.December 1995 Radiology, 197, 819-825.