Overview
It lies in the infraspinous fossa, caudal to the spine of the scapula, partly covered by the deltoideus. Its belly is crossed by tendinous sheets. Its tendon glides over a synovial bursa, on the caudal part of the greater tubercle, before inserting.
Origin
Infraspinous fossa (fossa infraspinata) of the scapula.
Insertion
Lateral surface of the caudal part of the greater tubercle of the humerus, distal to the supraspinatus insertion.
Action
Abducts and rotates the arm laterally. Depending on the position of the shoulder it helps flex or extend it, and it also works as a lateral collateral ligament of the joint.
Innervation
Suprascapular nerve (n. suprascapularis).
Clinical relevance
Suprascapular nerve injury causes atrophy of the supraspinatus and infraspinatus, leaving the spine of the scapula very prominent.