Everything You Need to Know About the Shoulder Complex

by Corey Pribyl, DPT, ACSM-EP

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When we think of the shoulder, we typically think of the ball and socket joint and pretty much just leave it at that. Really, there is so more to it. The shoulder is often referred to as the shoulder complex. This is because it is more than simply the ball and socket joint held together with the rotator cuff (not the rotary cup). It’s actually made of four individual joints, each responsible for different aspects of movement that, when performed in concert, results in clean, hopefully pain-free motion. The four joints that make up the shoulder complex are as follows:

1. Scapulothoracic Joint (STJ)

Scapula (shoulder blade) on posterior aspect of the thorax or rib cage; considered a “floating joint.”

The main focus of this post will be the STJ.

2. Glenohumeral Joint (GHJ)

Humeral head (ball of arm) on glenoid fossa (socket of shoulder blade). (We will expand on this joint in a future post.)

3. Acromioclavicular Joint (ACJ)

4. Sternoclavicular Joint (SCJ)

These joints connect the upper extremity to axial skeleton through the clavicle (collar bone) at acromion (ACJ) on the scapula to the sternum (SCJ).

Scapulothoracic Joint Motions:

  • Retraction: movement of the shoulder blade back around the rib cage toward the spine
  • Protraction: movement of the shoulder blade forward around the rib cage toward the mid axial line
  • Elevation: movement of the shoulder blade up on the rib cage
  • Depression: movement of the shoulder blade down on the rib cage
  • Upward rotation: in reference to the glenoid fossa which rotates upward on the rib cage with elevation of the upper arm
  • Downward rotation: in reference to the glenoid fossa which rotates downward on the rib cage

The importance of the STJ often seems understated. With the GHJ being a very mobile joint, the STJ is considered to be a stable joint. However, it’s also a dynamic joint and its motions need to be well-controlled to have optimal shoulder motions. We hear or use the term “back and down” a lot in reference to the shoulder blade with many exercises or motions. But in many cases, this cue reduces available arm movement and can even lead to stressful compensatory GHJ motions. By creating more ideal dynamic stability of the scapula, we are also able to improve the strength to the rotator cuff by allowing cuff musculature to have a better foundation to operate off of.

I would like to focus on motions of protraction, retraction and upward rotation of the scapulothoracic joint, the muscles that work together to create these movements, and how we can properly train them to create more efficient and safe movement of the upper extremity.


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Scapular retraction is the basis for pretty much all of the standard rowing movements. The trapezius and rhomboids are two muscles that act directly on the scapula for retraction. The much larger latissimus muscle is involved in retraction indirectly with pulling movements through its attachment to the humorous.

A common exercise used to train this movement is prone scapular retraction. Lying face down with your arms relaxed by your side, slowly draw the shoulder blades up off the table toward one another and the opposite back pocket. Do not pull through the arms or lift the chest. Pause briefly then slowly lower back down.

Once we have good control of scapular retraction we can progress to rowing movements. Here is a basic rubber band row:

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Standing with feet hip width apart, brace core and tighten glute muscles. Start with arms extended in front of you with shoulder blades open across the upper back. Try to keep upper traps relaxed. Initiate by drawing the shoulder blades back toward one another and slightly down. Do not let the upper traps dominate by drawing the shoulder blades up toward the ears. As the shoulder blades move, pull the elbows back keeping arms flared away from the ribs a bit. As you pull back, do not allow the chest/low ribs to lift excessively or the low back to arch.

There are all kinds of variations of rows and exercises that incorporate scapular retraction. As exercises are progressed to more complex movements and resistance is added, it’s important to remember the foundational movement of scapular retraction.


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The primary driver in rotation is the serratus anterior muscle. This movement is typically seen in our pressing movements.

The Serratus Punch is a common exercise to use to isolate the movement and engage the serratus muscle. This can be done lying on the back with arms over the chest or also done in weight bearing leaning into a wall. In either case, fully exhale and drive ribs down into the abdomen. Feel core muscles engage. Maintain core/ribs position and elbows straight reaching through your shoulder blades. You should feel shoulder blades sweep forward around the rib cage and not simply tilt forward or drift up toward the ears. This motion can then be progressed and incorporated into a standard push up.

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Start with arms fully extended, core and glutes tight. Lower your body down toward the surface, bringing your shoulder blades together and down. Elbows should flare about 20-30 degrees from the ribs. Go as deep into the motion as you feel comfortable. Reverse directions, focusing on driving through your chest muscles. Push away so arms are fully straight and continue to push through the armpits to open up your shoulder blades.

Upward Rotation

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Scapular upward rotation is essentially the result of a combination of movements and muscles pulling from different directions. Primarily coordinated engagement of the upper and lower portions of the trapezius muscle and the serratus anterior muscle create the force couple on the scapular that drives upward rotation. This movement is typically most prominent when reaching above the height of the shoulder. Proper upward rotation of the scapula reduces the likelihood of the rotator cuff becoming impinged and irritated.

The Scapular Wall Slide is a great exercise to begin working on this motion and can be progressed using a foam roller under the arms against the wall to begin working on more range of motion.

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Stand about 1-2 foot lengths from the wall with elbows against the wall and the tailbone slightly tucked. Fully exhale and drive ribs down into the abdomen. Feel core muscles engage. Maintain core, ribs down. Reach arms into the wall and chest away slightly. This, along with engaging the core and driving the ribs in, should cause a subtle round to the upper back. This is the natural curvature to the upper back and should be maintained throughout the movement. Reach up the wall and draw your shoulder blades down and around your rib cage. Maintain pressure through the forearm as you slide your arm up the wall. When lowering arms, make sure to maintain pressure from arms into the wall slightly. Only go as high as elbows can stay on the wall.

This same motion would be present during the lower phase of a pull up or when returning to the overhead position of a lat pull down or when lowering back down to the start position of a pull up. Scapular downward rotation would be the opposite motion and occur when returning from the overhead position. It is more emphasized during a lat pull down or pull up motion.

Lat Pull Down

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Brace core so ribs are held down but try to keep chest up (proud chest). Start out by letting your arms and shoulders relax, letting the machine pull your arms up. Then by using your shoulder blades, draw them down and back as if to put them in your back pockets without letting your chest and ribs rise or low back arch. As you pull the shoulder blades down, draw the elbows down and in toward the ribs. Return to start by straightening the arms but keeping shoulder blades low.

We hope this helps to shine some light on the shoulder and how important scapular motion is during rehab or training. If you’re struggling with your upper body training or experiencing shoulder pain while exercising, please reach out and let us help you get back to moving well and training hard!

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