Infraspinatus

From Ganfyd

Infraspinatus part of the rotator cuff of muscles around the shoulder joint.

Infraspinatus
System:	Muscle
Function:	stabilises shoulder, externally rotates arm
Origin:	infraspinous fossa of scapula
Branches:
Insertion:	capsule of the shoulder, greater tuberosity of humerus
Arterial supply:
Venous drainage:
Lymphatic drainage:
Innervation:	suprascapular nerve
Vertebral levels:
Search for Infraspinatus in Gray's.

Shape

Infraspinatus is a triangular muscle that fills the majority of the infraspinous fossa of the scapula. It arises by direct muscular attachments in its medial two thirds and by tendinous fibres from the surrounding ridges, as well as attachment to the infraspinatous fascia. Its fibres converge to a tendon which moves across the lateral spine of the scapula to pass across the posterior capsule of the shoulder joint.

Actions

• Lateral rotation of the humerus
• Stabilisation of the shoulder

Joints Affected

• Shoulder

Origin

• Medial two thirds of the infraspinous fossa of the scapula
• Infraspinatous fascia

Insertion

• Medial aspect of the greater tuberosity of the humerus
• Joint capsule of the shoulder

Nerve Supply

• Suprascapular nerve (C5, C6)

Relations

• Infraspinous fossa of the scapula

Superficially:

• Infraspinatous fascia
• Teres minor
• Teres major

Variations

• The tendon may be separated from the shoulder joint capsule by a bursa.

See Also

• Rotator cuff