Rotator cuff injury

Many people experience shoulder problems, with rotator cuff issues being among the most common.

The rotator cuff (RC) refers to a group of 4 muscles that originate on the scapula and insert into the humerus. These muscles are often known as the SITS muscles, named after the first letter of each: supraspinatus, infraspinatus, teres minor, and subscapularis. [1] Their primary function is to rotate the humerus and stabilize the head of the humerus within the joint. Additionally, they assist in flexing and abducting the arm. [2] Balanced strength and flexibility in each of the four muscles are essential for maintaining the proper function of the entire shoulder girdle. [3]

These muscles play a critical role in nearly every movement involving the shoulder joint. They help keep the head of the humerus centered in the glenoid fossa of the scapula, enhancing the range of motion in the glenohumeral joint and preventing mechanical obstruction.

The rotator cuff problems are so common, because raising the arm requires the engagement of a strong muscle- the deltoid. [4] It’s well-suited for this task, but as it works, it rolls the head of the humerus upward. In a healthy shoulder, this upward roll is balanced by muscles of rotator cuff that insert near the head of the humerus from below, such as the subscapularis and teres minor. However, if these muscles don’t engage properly, the head of humerus will roll upward, reducing the space available for the supraspinatus tendon to slide under the acromion. This increased friction weakens the tendon over time leading to injury.

The key to a healthy shoulder is proper timing and balance in the work of these muscles. To avoid rotator cuff injuries, it’s important to find a way to activate the subscapularis and teres minor while raising the arms. Then rotator cuff should will heal naturally.

  1. Gray,H. “Anatomy of the Human Body”, Philadelphia: Lea and Febiger, 1918; Bartleby.com, 2000
  2. Plachel, Fabian, i in. „Risk Factors for Rotator Cuff Disease: An Experimental Study on Intact Human Subscapularis Tendons”. Journal of Orthopaedic Research, t. 38, nr 1, january 2020, s. 182–91. PubMed Central, https://doi.org/10.1002/jor.24385
  3. Codman, E. A. “The Shoulder: Rupture of the Supraspinatus Tendon and Other Lesions in or about the Subacromial Bursa”, Thomas Todd Co., Boston, 1934
  4. McCausland, Cassidy, i in. „Anatomy, Shoulder and Upper Limb, Shoulder Muscles”. StatPearls, StatPearls Publishing, 2024. PubMed, http://www.ncbi.nlm.nih.gov/books/NBK534836/
biomechanicsdeltoidhumerusinjurypainrotationrotator cuffshouldersubscapularissupraspinatusteres minor
Common Issues