CHAPTER 15: Shoulder Joint and The Arm

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Glenohumeral Joint


The shoulder joint is a synovial joint of the ball-and-socket (enarthroidal) type. Functionally multiaxial

Articular surfaces  

  1. The hemi spherical head of the humerus (1)
  2. The glenoid cavity of the scapula (2). ( The rim of the glenoid cavity is deepened by the glenoid labrum )


Glenoid Fossa  

Concave vertically and A/P
Articular surface represents just over 1/3 that of humeral head
The Gleniod labrum, triangular in cross-section like the hip, surround and deepens the glenoid fossa

Head Of Humerus  

Forms 2/5 of a sphere
Regardless of position only 1/3 of head is in contact with gleniod at any one time.

Joint surface markings

The midpoint of the joint is approximately 1cm lateral to the apex of the coracoid process
A vertical line slightly concave laterally through this point gives an indication of the joint line

Note : The joint is unstable: it is built for mobility, not stability, and dislocation is more common at this joint than at any other in the body.