Posterior Shoulder Dislocation: Symptoms & Presentation

Instructor: Dan Washmuth

Dan has taught college Nutrition, Anatomy, Physiology, and Sports Nutrition courses and has a master's degree in Dietetics & Nutrition.

A posterior shoulder dislocation occurs when the bone of the upper arm dislocates from the shoulder joint in a posterior (backward) direction. In this lesson, learn about the symptoms and presentation of this type of injury.

Posterior Shoulder Dislocation

Kate is a 74-year-old widow who lives by herself in the same home she has lived in for the past 50 years. She takes great pride that she had been able to live independently since her husband died 4 years ago, taking care of herself with minimal help from her friends and family.

During a recent trip to the grocery store, Kate slipped on a wet spot in the dairy section and fell directly onto her outstretched right arm. When Kate tried to get up, she realized that she could not move her right arm and her shoulder was in a lot of pain.

The store manager saw Kate fall, and quickly ran to help her. Kate told him that she couldn't move her arm and that she was in a lot of pain, which caused the manager to instantly call 911. An ambulance quickly arrived and took Kate to the hospital. At the hospital, x-rays of her shoulder and arm revealed that she had a posterior shoulder dislocation.

The shoulder joint is formed when the head of the upper arm (humerus) meets with the shoulder blade (scapula) and the collarbone (clavicle). A posterior shoulder dislocation occurs when the head of the humerus is moved in a posterior (backward) direction from its normal location in the shoulder joint. The main causes of this type of injury are car accidents, sports collisions, violent seizures, or falls onto outstretched arms like the one Kate sustained. Additionally, posterior shoulder dislocations are often associated with shoulder fractures as well.

The shoulder joint is made up the humerus, scapula, and clavicle.
shoulder joint

Posterior Shoulder Dislocations: Symptoms

The primary symptom of a posterior shoulder dislocation is pain. This pain is usually a very intense, sharp pain that increases when a person tries to move their arm or shoulder. Other symptoms of this injury include:

  • Swelling
  • Inability to move arm and shoulder
  • Numbness and tingling
  • Shoulder deformity

Posterior Shoulder Dislocations: Presentation

During x-ray evaluations of a posterior shoulder dislocation, the head of the humerus will often appear to be in the shape of a light bulb. During a physical examination, a person with a posterior shoulder dislocation will usually have difficulty with external rotation of the arm. External rotation of the arm is the movement where the arm is bent at a 90 degree angle and the forearm and hand are rotated away from the body.

The head of the humerus will often look like a light bulb in an x-ray of a posterior shoulder dislocation.
light bulb

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