Infraspinatus and supraspinatus

The supraspinous and infraspinatus muscles are the main stabilisers of the scapula and the shoulder joint.

Supraspinatus

Origin: The superior aspect of the scapula

Inserts: into the humerus.

Function: Extends the shoulder joint and works as an antagonist to the deltoid muscle.

Infraspinatus

Origin: The infrascapula fossa

Inserts: into the humerus.

Function: Involved in rotating the forelimb laterally and abducting the forelimb.

Soreness: Atrophy of both of these muscles is visible as the scapula spine becomes more prominent. Weakness or tension in these muscles can cause instability of the shoulder and result in the horse struggling the advance the limb and therefore a shortened stride. The horse may also “drop their shoulder” on a circle.

Massage can help to relax, relieve pain and discomfort in these muscles and therefore improve the functionality of these muscles which in turn would improve performance and comfort during exercise.