The Forgotten Rotator Cuff Muscle, Part 1

By Ben Benjamin, PhD
January 8, 2014

The Forgotten Rotator Cuff Muscle, Part 1

By Ben Benjamin, PhD
January 8, 2014

The teres minor is the weakest of the four rotator cuff muscles. It is the brother of the infraspinatus because they mostly do the same thing; lateral rotation. It gets a lot of use when you turn the steering wheel of your car or you reach high up on a shelf to get something. The teres minor works more at slightly different angles from the infraspinatus and assists in adducting the arm.

Try this. Put your hand on top of your head with your thumb facing down toward the floor and put your other hand on the ulna side of your wrist for resistance and then push up with the bottom hand. You are now engaging a number of muscles but more of the teres minor than with any other motion. The teres minor originates at the dorsal surface of the axillary border of the scapula, that's the lateral most border.

Its fibers run obliquely upward and laterally; the upper fibers end at the teres minor tendon which is inserted into the inferior facet of the greater tubercle of the humerus, that's the little bump at the most lateral edge of the greater tubercle. The tendon of the teres minor passes across the gleno-humeral joint, and joins with the posterior part of the joint capsule. The infraspinatus and teres minor attach to the head of the humerus; and form posterior part of the rotator cuff.

They help hold the humeral head into the glenoid cavity of the scapula. They work along with the posterior deltoid muscle to laterally rotate the humerus, as well as perform adduction and assist in extension of the arm behind you. Sometimes the teres minor is actually fused with the infraspinatus.

Now that you know a little bit about this muscle and how it functions, in my next article we will talk about how to assess and treat this little known, weak muscle.