Rotator Cuff Injuries: Causes and Risk Factors

The causes of rotator cuff injuries are grouped into two major categories:

1. Traumatic injuries
2. Degenerative injuries

Traumatic injuries are one-time events—often unforeseeable accidents—and degeneration occurs over time.

Several risk factors, including age, general health, and shoulder joint exertion are associated with muscle or tendon injury.

Rotator Cuff Injury Causes

The common causes of rotator cuff injuries are described below.

An acute injury caused by a single traumatic event

A rotator cuff can be injured in a single trauma, such as trying to break a fall with an arm outstretched, lifting a heavy weight, or activities that place a tremendous amount of force or strain on the shoulder, such as holding a waterskiing tether.

Degeneration over months or years

As people age and/or overuse their shoulders, the rotator cuff degenerates—especially in people over 40 and those in occupations that require frequent raising and lowering of the arm, such as roofing or carpentry.

Tiny tears develop in the rotator cuff, making it weaker and more prone to larger tears. These larger tears can occur without any notable trauma.

Chronic microtrauma from shoulder impingement

Rotator cuff degeneration is sometimes associated with impingement. Shoulder impingement syndrome is an umbrella term that describes the painful pinching or squeezing of muscles, tendons, or other soft tissue that is sandwiched between two bones: the bottom of the acromion (the top outer edge of the shoulder) and the top of the shoulder’s ball-and-socket joint (glenohumeral joint). This space is called the subacromial space.

See Shoulder Impingement Symptoms

The rotator cuff passes beneath this small subacromial space and can become inflamed and damaged when compressed under tension and pressure.

Trauma from repetitive throwing motions

Rotator cuff injuries are common in athletes involved in throwing sports where high-velocity arm motions are used to propel objects. A common example is baseball, where a pitcher’s specialized throwing motions lead to rotator cuff injuries in the following ways:

• In the late cocking/early acceleration phase, just before throwing a ball, a pitcher’s arm is lifted away from the body and rotated outward. This motion can cause compression of the rotator cuff as well as the shoulder’s labrum, a ring of tough cartilage that lines the shoulder socket.
• During the deceleration phase, immediately after the ball is released, the rotator cuff experiences excessive overloading, which can result in overstretching or tearing.

These motions are likely to cause chronic microtrauma and damage the muscles and tendons over time or result in an acute injury if excessive force is used while throwing.

Risk Factors of Rotator Cuff Injury

People with rotator cuff injuries tend to have one or more of the following risk factors:

• Age. Degenerative rotator cuff injuries are common in middle-aged and older people.
  • Around 62% of people over age 80 have rotator cuff tears.¹May T, Garmel GM. Rotator Cuff Injury. [Updated 2023 Jun 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK547664/
  • By age 60, more than half the patients with tears on one shoulder tend to develop tears on the other shoulder as well (bilateral tears).¹May T, Garmel GM. Rotator Cuff Injury. [Updated 2023 Jun 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK547664/
  • The tears tend to progress faster in patients over 60 years.¹May T, Garmel GM. Rotator Cuff Injury. [Updated 2023 Jun 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK547664/
• Occupation and sports. The injury is more common in people who engage in repetitive overhead shoulder motions, such as hammering, painting, swimming, playing tennis, or pitching a baseball.
• Shoulder arthritis. People with shoulder arthritis are likely to develop shoulder instability, muscle weakness, and abnormal bone growths, called osteophytes. All of these factors increase stress on the rotator cuff, making it more prone to injury.
• Family history. People with a family member diagnosed with rotator cuff injury are likely to develop the condition.
• Poor posture. Sitting or standing in a hunched or forward bending posture increases loads on the neck (cervical spine) and shoulder, causing inflammation of the rotator cuff muscles over time.
• Smoking. A higher incidence of rotator cuff injuries is seen in people who regularly smoke.

In younger athletes, traumatic shoulder injuries may cause rotator cuff tears and SLAP tears to occur together.

See SLAP Tear Symptoms