The Shoulder Complex

The Shoulder Complex
Muscles, attachments, kinesiology, massage treatments
By Roger Fontaine February 2007 (all rights reserved)

This article does not address injuries to the actual gleno-humeral joint cartilage or ligaments as those are beyond the scope of massage therapy and require medical or surgical intervention. This article deals with the muscles, kinesiology and massage treatment of the shoulder muscles.

Let’s start by listing the muscles which surround the shoulder joint then we will define what makes up the joint itself.


On the front is the pectoralis major which stabilizes the front of the shoulder by joining the sternum with the collar-bone (clavicle) and the arm (humerus).

There are two pectoralis muscles, the second being the minor. It originates from the 3-5th rib and attaches on the acromion process which is the protruding finger which is prominent on the top of the shoulder blade (scapula).

The muscle which counters the pectoralis on the back is the rhomboid major and minor.
These muscles originate on the spinous or vertebral edge of the scapula and attaches on the sides of the thoracic vertebrae. The minor rhomboid attaches to T1-3 while the major attaches to vertebraes T3-5.They angle downward from outside to inside of the body, lateral to medial.
Also on the back is the trapezius. This is a large muscle with three components: an upper, middle, and lower. The upper attaches to the occiput of the head and proceeding down the nexk does a twist at the inner corner of the scapula and then attaches to the outside edge of the scapula. Its involvement is to elevate the scapula shoulder-arm complex. The middle trapezius assists the rhomboids and is more superficial to the surface. The lower attaches at the top to the lower edge of the spine of the scapula and then proceeds downward in a lateral direction to the spinous process of the vertebrae and attaches from thoracic 6-12. This part of the muscle is used to lower the scapula.

The next most important muscles which are involved with the shoulder are the rotator cuff muscles. These surround the humerus, are anchored on the scapula and loosely hold the humerus in the gleno-humeral socket. This joint is loosely-packed to allow the most range of motion, as is evident with the 360 degree rotation of the arm.

The anterior rotator cuff orginates beneath the scapula and is called the sub-scapularis. It attaches to the front of the humerus. The top of the humerus is maintained in its place by the supra-spinatus which originates just above the spine of the scapula and attaches at the top of the humerus bone. It passes beneath the hook on the acromion process before attaching there. This offers it some protection.

The other posterior rotator cuff muscle is just below the spine of the scapula and is called the infra-spinatus. It covers the outside lower part of the scapula and attaches to the back of the humerus near the joint capsule.

Beneath these muscles the gleno-humeral joint is enclosed in a synovial joint capsule and surrounded with ligaments on the back, top, and front. However the weakest point on the joint is the front, and subsequent to tearing the front ligaments the arm can dislocate and more seriously protrude anteriorly ( towards the front) with a seriously strong enough impact to the torso or arm. Ouch!

Two other main muscles which surround the shoulder joint are the biceps brachii and the triceps. Both of these muscles are on the front and back respectively of the humerus or arm. The biceps brachii on the front has two attachments on the shoulder, one short, and one long. The short one attaches on the front of the scapula and the long on the top via a long tendon.
The arm also has the brachio-radialis and brachialis which are on either side of the biceps brachii and which assist the arm to flex. They also attach on the front of the scapula and provide some strength to the arm-shoulder joint. On the back of the arm is the lattisimus dorsi which assists to extend the arm backwards. It attaches to the inside front of the arm near the shoulder gleno-humeral joint and passes under the arm, through the arm-pit, and ataches to the ribs on the side of the scapula, and over the scapula.
The teres minor and major are both arm rotators. The teres minor and teres major both attach on the arm and the outer edge of the scapula.

The teres major attaches under the armpit to the front of the humerus next to the latissimus dorsi and it rotates the arm internally when contracting.

The teres minor attaches onto the top-back of the arm and when contracting rotates the arm externally.

So let’s add up all the muscles which we’ve listed so far to see how many we have.
Pectoralis major, pectoralis minor, rhomboid major, rhomboid minor, trapezius,
sub-scapularis, supra-spinatus, infra-spinatus, biceps brachii, triceps, brachi-radialis, brachialis, latissimus dorsi, teres minor, teres major. That makes fifteen muscles.


The movement of the arm on the shoulder works on many planes and axes. The axes are the x,y,and z.
The ‘X’ axis is the easiest one to learn as it moves the arm from front to back, or sagitally (the sagittal plane is a front to back cross-section dividing the body left from right). When the arm is moved from resting at the side frontwards towards the head is called flexion. When the arm is moved backwards behind the body is called extension. The muscles involved with flexion are the front-anterior muscles: biceps, brachialis, radio-brachialis. The muscles involved in extension are the latissimus dorsi and triceps.

The ‘Y’ axis involves the movement of the arm along the frontal plane( the frontal plane cuts the body front to back vertically), from the side at rest into abduction raising the arm to the top of the head. The muscles involved are the supra-spinatus, deltoid and trapezius. When the arm is taken across the chest in horizontal adduction the muscles involved are the pectoralis major, pectoralis minor, serratus, and anterior deltoid.

The ‘Z; axis involves the motion of the rotation of the arm. With the arm fully extended and raised to shoulder height the ‘z’ axis goes through the body from left arm to right arm. When the arm is internally rotated , starting with palm facing front and thumbs up rotating arms till thumbs are down and palms back, the muscles involved in this motion are the teres major and some latissimus dorsi.
When rotating backwards or exteriorly the muscles involved is the teres minor.

Rotator cuff stabilizers:

While these muscles mentioned above are moving the arm through its range of motions the rotator cuff muscles are stabilizing the arm by keeping it tightly in the gleno-humeral joint.
There are three principal rotator cuff muscles: the supraspinatus, on the top which lifts the arm as well. The subscapularis, which is beneath the scapula (shoulder-blade), the infra-spinatus which is over the scapula, and teres minor to a lesser degree because of its attachments offers less stabilization than the other three muscles yet can be considered an accessory.

Because of the loosed-pack nature of the shoulder joint meaning that because the joint is shallow there is maximum flexibility and motion of the joint, as can be experienced by performing a 360 degree rotation of the arm either in flexion or extension.
Although it is not without some amount of resistance that this motion is performed because there are always antagonists to agonists, ie: the agonists are the muscles which are contracting while the antagonists are the opposing muscles which are relaxing. So it is quite a complex feat that when we perform the arm circumrotation that we do not experience some pain or limitations of movement.
Which is precisely what we experience when we have shoulder injury or limitation causing pain.


I have found in my practice as a massage therapist in a fitness centre setting that most of the injuries to the shoulder are involving tendonitis, bursitis, and muscle contractures and adhesions.

The four types of injuries result from the repetitious nature of weight training or strengthening. There is placed an excessive strain on the tendons, bursas and muscles resulting in inflammation, tearing, compressing of bursae, and repeated contractures of muscles and resulting adhesions.

The tendonitis and bursitis can only be healed by stopping the straining and applying ice to relieve the inflammation process. The muscles can be treated for contractures and adhesions with massage.

Often clients of the fitness centre refuse to modify or reduce their weight training to alleviate the injury and persist to train through the pain magnifying their injury and pain. Those who choose to stop their weight training long enough for the inflammation process to subside and heal have good to complete recovery.

I use general massage techniques to the pectoralis, deltoid, latissimus dorsi, biceps and triceps, and other superficial muscles which surround the shoulder joint.

This then allows me to pay attention to the rotator cuff muscles. What I can do is reduce muscle tone, work out some contractures and adhesions in the deltoids and pectoralis and rotator cuff muscles taking the strain off the tendons and bursae. Then time does the healing with a much reduced weight training regimen or with complete termination of weight training until the inflammation of tendons and bursae occurs, which may take one to four weeks depending on the severity of the tendonitis/bursitis.

I found that weekly massage treatments of one-half hour to one-hour depending on the client is adequate for complete treatment of this condition.
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