Overview
It lies in the infraspinous fossa, caudal to the spine of the scapula, partly covered by the scapular part of the deltoideus. Its tendon glides over a synovial bursa before inserting.
Origin
Infraspinous fossa (fossa infraspinata) of the scapula.
Insertion
Lateral surface 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
Infraspinatus contracture, typical of working and hunting dogs, produces a characteristic gait with the elbow adducted and the forearm rotated outward.