The rotator cuff muscles are a group of muscles that make up the major muscles that rotate the arm and stabilize the shoulder joint. There are four muscles that make up this group: supraspinatus muscle, infraspinatus muscle, teres minor muscle and the subscapularis muscle. Injury to the rotator cuff muscles are very common with 9.7% in people 20 years old or younger, and 62% in people over the age of 80.
The teres minor muscle originates from the lateral (away from midline) portion of the scapula (shoulder blade). The muscle inserts into the proximal (top) humerus bone near the insertion sites of the infraspinatus and the supraspinatus muscles. It is innervated by the axillary nerve which stems from the cervical 5th and 6th nerve roots. It’s main action is to externally rotate the shoulder/arm but it also helps in overall stability of the shoulder joint. It is synergistic with the infraspinatus muscles in its function. The teres minor provides more external rotation when the arm is abducted (raised to side) to 90 degrees, to differentiate from the infraspinatus.
Like the other rotator cuff muscles, the teres minor muscle is more likely to be injured in people that do repetitive motions of the shoulder. Including painters, golfers, swimmers, tennis players, and throwing athletes. Injuries can include a tear of the muscle either partially or completely. There can be inflammation of the muscle and tendon which causes tendonitis. If the infraspinatus is injured it could cause or be secondary to a rotator cuff impingement syndrome, where multiple rotator cuff muscles are injured.
Stretches for the infraspinatus include sleeper stretches and cross-body shoulder stretches. To strengthen the teres minor muscle exercises such as external rotation of the arm at 90 degrees with a band or dumbbells will help. When trying to rehabilitate an injured rotator cuff muscle, starting with restoring normal range of motion and strengthening the “scapular stabilizers” is always an important starting point. All these exercises should be done with the guidance of your health care provider to progress in a safe way.
Williams JM, Sinkler MA, Obremskey W. Anatomy, Shoulder and Upper Limb, Infraspinatus Muscle. [Updated 2020 Aug 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513255/