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 the group: supraspinatus muscle, infraspinatus muscle, teres minor muscle and the subscapularis muscle. Injury to the rotator cuff muscle is very common with 9.7% in people 20 years old or younger, and 62% in people over the age of 80.
The infraspinatus muscle originates from the inferior (lower) portion of the scapula (shoulder blade) and inserts into the proximal humerus bone. It is innervated by the suprascapular 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 provides more external rotation with the arm in a neutral position (arm by your side) then if elevated.
The infraspinatus muscle is more likely injured in people that do repetitive motions of the shoulder; including painters, carpenters, swimmers, tennis players, and throwing athletes. There is a higher likelihood of injuring the infraspinatus as you get older. 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 infraspinatus muscle exercises such as external rotation 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/