Rotator Cuff Muscles, Scapular Support Muscles, Shoulder Decompression, Possible Shoulder Pain Fix Defined

Dr. Corey Hoffner explains exercises that may help control shoulder pain caused by external rotation and other shoulder motions, too (YouTube@drchoffnerptsc).

Pain with external rotation of the shoulder likely means that the shoulder joint is compressed, and that the rotator cuff is not adequately controlling the multi-dimensional movement of the shoulder (external rotation, internal rotation, flexion, and extension of the shoulder). Decompressing a shoulder joint is defined as re-establishing a position of the upper arm connection to the shoulder blade in the safe and instant center position, which provides a shoulder joint condition that hopefully becomes pain free.

The rotator cuff consists of four small muscles (supraspinatus, infraspinatus, teres minor, subscapularis) that are involved (along with larger muscles: biceps, triceps, and deltoids) with the connection of the arm (humerus) to the shoulder blade (scapula). The main function of the rotator cuff muscles is to keep the upper ball-shaped end of the humerus that is positioned in a concave surface of the scapula in an instant center. The instant center or instantaneous center is a position of the upper arm "ball" that stays clear of the joint surfaces associated with the scapula. Theoretically in physics, there is a point at the center of the upper arm "ball" that has zero velocity because the "ball" rotates perfectly in a stable center while the upper arm moves in all different directions. If the upper arm "ball" isn't held in an instant center during the multi-dimensional motion capabilities of the arm at the shoulder joint, the upper arm "ball" may bang against the scapula surfaces, which can damage rotator cuff tendons and the biceps tendons, and create imbalances of muscles that cause limited capabilities of shoulder motion.

The anatomical name for the ball of the upper arm is the head of the humerus (or humeral head).

The larger muscles (biceps, triceps, and deltoids) provide the greater strength and power capabilities of upper arm motion at the shoulder joint are like the mechanisms that turn the wheels of a car, but the rotator cuff muscles provide stability and backup fine control like the shock absorbers of a car.

The Four Rotator Cuff Muscles

Supraspinatus helps lift the arm out to the side (abduction) while depressing and providing stability of  the upper arm "ball" so the upper arm doesn't collide with the scapular joint surface (while maintaining the instant center). The supraspinatus also assists with external rotation of the upper arm; and also, works to help prevent the upper arm from sliding out and down when the arm is hanging normally at the side, or when you are carrying something while your arm is hanging down at your side.

Infraspinatus helps rotate the arm backward by causing external rotation and backward motion of the upper arm while maintaining the instant center.

Teres Minor causes external rotation, arm adduction (pulls the arm down to the side from a raised position), and controls the instant center while also helping prevent shoulder dislocation.

Subscapularis is the only rotator cuff muscle that causes internal rotation of the upper arm,  and is also the largest rotator cuff muscle. The subscapularis also causes arm adduction -- bringing the arm down to the side from a raised position with the Teres Minor. The subscapularis functions to prevent shoulder dislocation (especially overhead arm positioning) and maintain the instant center of the upper arm "ball".

Scapular Support Muscles

The primary muscles that support and stabilize the scapula (shoulder blade) include the trapezius, serratus anterior, levator scapulae, and rhomboids. The scapular support muscles help to raise or lower the entire shoulder joint so that all arm motion doesn't need to happen at the instant center of the humeral head. The scapular support muscles also help the scapular slide forward (protract) the entire shoulder joint so that all arm motion doesn't need to happen at the instant center of the humeral head.  The scapular support muscles also help the scapular slide backward toward the spinal column (retract) the entire shoulder joint so that all arm motion doesn't need to happen at the instant center of the humeral head.  The scapular support muscles also help lock down the scapula on the back when necessary. The lock down of the scapula may be fixed in a holding position or dynamic, as in a heavy strength motion.

Three exercises can help decompress the joint, build scapular support, and reload external rotation safely.

Decompress the shoulder joint by bending over at the hips and hanging your arm while holding a medium weight kettle bell and swing your arm safely forward and backwards. You can hold a dumbbell instead if you don't have a kettlebell, although the kettlebell might provide a little more momentum leverage because the mass of kettlebell is extended further beyond your hand compared to a dumbbell.

Build scapular support and control by pressing on a Swiss Ball or Stability Ball while sliding forward while kneeling with your forearms supported on the Stability Ball. This action fires or activates the serratus anterior in a closed-chain kinetic position. A closed kinetic chain position is a body stance or exercise movement that is performed while the hand or foot (or both hands or both feet) are fixed against a stationary surface like the ground, a wall, or a machine base, which involves multi-joint motion engagement, and compressive joint forces. This exercise re-introduces compression of the shoulder joint in a safe manner, hopefully.

Reload external rotation without shoulder compression by lying prone (face down) with shoulders laterally abducted 90 degrees, and elbow flexed 90 degrees.

Dr. Corey Hoffner explains an injured rotator cuff and explains three exercises that might help if the injury isn't too severe: 1) Banded Distraction with Kettle Bell, 2) Assisted Forward/Abducting Flexion with Stick, and 3) Isometric External Rotation (YouTube@drchoffnerptsc).

Dr. Corey Hoffner is a doctor of physical therapy and Certified Strength and Conditioning Specialist. 

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