Glenohumeral Joint

Question 1

Classify the glenohumoral joint

Answer 1

Polyaxial synovial ball and socket joint, capable of 3 degrees of freedom

Question 2

Briefly describe the articular surface of the glenoid fossa

Answer 2

Small pear shaped depression at the supra lateral aspect of the scapula, covered in hyaline cartilage – thicker at periphery.
Faces laterally, anteriorly and slightly superiorly
Glenoid labrum - fibrocartilaginous rim; deepens articular surface of glenoid fossa

Question 3

State the movements which occur at the glenohumeral joint (full planar range)

Answer 3

Flexion / Extension, Abduction / Adduction, Medial / Lateral rotation
Could add horizontal flexion and horizontal extension

Question 4

Name the ligaments which assist stability at this joint

Answer 4

Capsular ligaments
		○ Anterior capsule:
			§ Superior glenohumeral
			§ Middle glenohumeral
			§ Inferior glenohumeral
		○ Transverse humeral - bridges gap between greater & lesser tubercles at upper end of intertubercular sulcus of humerus

Accessory ligaments
○ Coracohumeral - strong flat band from lateral border of coracoid process to transverse humeral ligament, adjacent anatomical neck
○ Coracoacromial -strong triangular ligament passing between coracoid and acromial processes above head of humerus

Question 5

Briefly describe the articular surface of the head of humerus

Answer 5

The head of the humerus is hemispherical , faces superiorly medially and posteriorly, covered with hyaline cartilage which is thicker centrally and thinner at the periphery.

A little more than 1/3 of head of humerus articulates with glenoid fossa at any time, but is deepened by the fibrocartilage glenoid labrum.

Question 6

State the attachments of the capsule of the glenohumeral joint

Answer 6

Loose fibrous capsule surrounds glenohumeral joint attaching to glenoid labrum, anatomical neck of humerus and articular margin of humeral head, except inferiorly where it joins the upper part of the humeral shaft 1cm below articulations margin

Inferiorly is a fold (redundant capsule) that only becomes taught during flexion/extension, allowing full ROM

Synovial membrane attached to articular margins of both bones covering all non-articular surfaces, continuous with subscapular and infraspinatus bursae, also with subacromial, subdeltoid bursae (latter 2 do not communicate with shoulder joint)

Thickened anteriorly by superior, middle & inferior glenohumeral ligaments
tendons of the rotator cuff muscles spread out over the capsule , blending with it near humeral attachments

Question 7

Factors of shoulder instability

Answer 7

• Shallow glenoid fossa
	• Large head of humerus
		○ Hemispherical
		○ Lack of bony congruency - 1/3 articular surface only ever in articulation with glenoid fossa at any one point
	• Loose articular capsule

Question 8

Solutions of shoulder instability

Answer 8

• Glenoid labrum - deepens glenoid fossa
• Ligaments - anterior humeral ligts
• Rotator cuff muscles - key to stability & control within glenohumeral joint

Question 9

Name pathologies caused by shoulder instability

Answer 9

• Anterior shoulder dislocation - Head of humerus slips anteriorly out of glenoid fossa when arm is forcibly LR & ABD
○ Pressure on axillary nerve may lead to deltoid, teres minor issues

• Posterior shoulder dislocation
○ Less common
○ Often seen as after electrocution

• Fractured surgical neck of humerus - usually occurs from FOOSH; more likely in elderly

Frozen shoulder (adhesive capsulitis)
• Capsule becomes less mobile - restricted movements in all directions caused by Thickening of capsule in its entirety - capsular pattern of reduced mobility
○ A sign/diagnosis for frozen shoulder
• Symptoms of soft tissue around shoulder joint becoming painful, stiff, inflammed
• May be caused by trauma or come about from lack of movement in shoulder (sudden vs gradual onset)

Question 10

Name attachments & function of glenohumeral ligaments

Answer 10

Superior- passes from upper glenoid margin to upper surface of lesser tubercle
Middle - arises below the superior lig and passes to anterior surface of lesser tubercle
Inferior - best developed lig; passing from glenoid margin to anteroinferior part of anatomical neck

Thickens joint capsule anteriorly and limit lateral rotation (all) & ABD (inferior, middle), ADD (superior)