Which two actions are attributed to the infraspinatus muscle?

The infraspinatus muscle is primarily responsible for lateral rotation of the shoulder joint and stabilizing the shoulder. Its primary action is to allow the shoulder to rotate outward, which is a characteristic of external or lateral rotation. While the infraspinatus assists with minor stabilization of the shoulder in various movements, the main actions attributed to it do not include flexing or extending the shoulder directly; those actions are more characteristic of other muscles, such as the deltoid.

The options reflect various movements that the shoulder joint can perform, but none accurately convey the main functions of the infraspinatus. The muscle does not flex or extend the shoulder; rather, it is crucial for externally rotating the arm at the shoulder joint and contributing to overall shoulder stability. Thus, understanding the primary role of the infraspinatus clarifies why flexing and extending actions would not apply.