Shoulder Joint: Flexion, Extension, Abduction, Adduction, and Rotation

What are the 5 ranges of motion of the shoulder joint?

The highly mobile glenohumeral (shoulder) joint primarily performs five fundamental ranges of motion: flexion, extension, abduction, adduction, and rotation (internal and external), each crucial for the vast functional capacity of the upper limb.

Understanding the Shoulder Joint's Mobility

The shoulder is a complex articulation, primarily centered on the glenohumeral joint, a ball-and-socket synovial joint formed by the head of the humerus (upper arm bone) and the glenoid fossa of the scapula (shoulder blade). Its design prioritizes mobility over stability, allowing for the widest range of motion of any joint in the human body. This extensive mobility is essential for activities ranging from throwing and lifting to intricate fine motor tasks. Understanding its primary movements is foundational for effective training, rehabilitation, and injury prevention.

1. Shoulder Flexion

Definition: Shoulder flexion is the movement of the arm forward and upward in the sagittal plane, away from the anatomical position.

Movement Description: Imagine raising your arm directly in front of you, bringing it from your side up towards your head. The range typically extends from 0 degrees (arm at side) up to approximately 180 degrees (arm straight overhead).

Key Muscles Involved:

• Primary Movers: Anterior deltoid, pectoralis major (clavicular head), coracobrachialis.
• Synergists: Biceps brachii (long head).

Practical Examples:

• Raising your hand to ask a question.
• Performing a front raise exercise.
• Reaching for an object on a high shelf.

2. Shoulder Extension

Definition: Shoulder extension is the movement of the arm backward in the sagittal plane, returning from a flexed position or moving behind the torso.

Movement Description: This is the opposite of flexion. If your arm is raised in front of you, extension brings it back down to your side and then continues to move it behind your body. The range typically extends from 0 degrees (arm at side) to about 45-60 degrees behind the body.

Key Muscles Involved:

• Primary Movers: Posterior deltoid, latissimus dorsi, teres major.
• Synergists: Triceps brachii (long head).

Practical Examples:

• Pulling an object towards your body (e.g., a rowing exercise).
• Pushing off the ground when getting up from a prone position.
• The backward phase of a walking or running arm swing.

3. Shoulder Abduction

Definition: Shoulder abduction is the movement of the arm away from the midline of the body in the frontal (coronal) plane.

Movement Description: Imagine lifting your arm directly out to the side, away from your body, bringing it up towards your head. The range typically extends from 0 degrees (arm at side) up to approximately 180 degrees (arm straight overhead). This full range involves not only glenohumeral movement but also scapulohumeral rhythm, where the scapula rotates upward to allow the arm to reach full overhead abduction.

Key Muscles Involved:

• Primary Movers: Middle deltoid, supraspinatus (initiates abduction).
• Synergists: Trapezius, serratus anterior (for scapular upward rotation).

Practical Examples:

• Performing a lateral raise exercise.
• Reaching out to the side to pick something up.
• Raising your arm to signal "stop."

4. Shoulder Adduction

Definition: Shoulder adduction is the movement of the arm towards the midline of the body in the frontal (coronal) plane.

Movement Description: This is the opposite of abduction. If your arm is out to the side, adduction brings it back down towards your body, often crossing the midline. The range typically extends from 180 degrees (full abduction) down to 0 degrees (arm at side), and can continue to approximately 45 degrees across the body.

Key Muscles Involved:

• Primary Movers: Pectoralis major, latissimus dorsi, teres major.
• Synergists: Coracobrachialis, subscapularis, triceps brachii (long head).

Practical Examples:

• Bringing your arm down after reaching overhead.
• Performing a pull-down or chest fly exercise.
• Crossing your arms in front of your body.

5. Shoulder Rotation (Internal and External)

Definition: Shoulder rotation refers to the pivotal movement of the humerus around its longitudinal axis within the glenohumeral joint. It encompasses two distinct directions: internal (medial) rotation and external (lateral) rotation.

Movement Description:

• Internal (Medial) Rotation: The anterior surface of the humerus rotates inward, towards the midline of the body. If your elbow is bent 90 degrees and tucked into your side, internal rotation brings your forearm across your body. The range is typically 70-90 degrees.
• External (Lateral) Rotation: The anterior surface of the humerus rotates outward, away from the midline of the body. With your elbow bent and tucked, external rotation brings your forearm away from your body. The range is typically 90-100 degrees.

Key Muscles Involved:

• Internal Rotators: Subscapularis, pectoralis major, latissimus dorsi, teres major, anterior deltoid.
• External Rotators: Infraspinatus, teres minor, posterior deltoid.

Practical Examples:

• Internal Rotation:
  • Reaching behind your back (e.g., to scratch your lower back).
  • The follow-through of a tennis serve or baseball pitch.
  • Performing an internal rotation exercise with a resistance band.
• External Rotation:
  • Throwing a ball (cocking phase).
  • Combing your hair behind your head.
  • Performing an external rotation exercise for rotator cuff strengthening.

Importance of Full Range of Motion

Understanding and actively training through these five primary ranges of motion is vital for maintaining shoulder health, optimizing athletic performance, and preventing injuries. Limited range of motion can lead to muscular imbalances, impingement syndromes, and reduced functional capacity. Conversely, excessive mobility without adequate stability can increase the risk of dislocations. A balanced approach that incorporates strength training, flexibility, and proper movement patterns across all shoulder planes is key to a robust and healthy shoulder joint.