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Myth Busting With the SC joint

Updated: Sep 1, 2020

When was the last time you considered the sternoclavicular (SC) joint when working with a patient? If someone doesn’t complain of pain or clicking in this area do you check it off your list of things to consider from a movement perspective?

As the articulation between the medial aspect of the clavicle and the manubrium of the sternum, the SC joint is classically described as a synovial, saddle-shaped joint. You’ll find out in this blog post that its structure and function are more complex.

The SC joint helps the clavicle function as a bony strut between the sternum and the scapula, allowing for our great ability to reach away from our body. It’s claim to fame as the sole skeletal articulation between the axial skeleton and the upper limb is more than a fun fact.

When contemplating the kinematics and pathology of the shoulder complex we obsess over scapular movement. The kinematics of the SC joint are described in textbooks but rarely consider clinically.

If the sternoclavicular joint is more involved in movement and function than many of us give it credit for, why is this the case? I believe the reason is multifactorial, due in part to insufficient information but also misconceptions about the joint and broader topics in the realm of movement science.

This post is another opportunity to question our beliefs and do some myth busting, this time with the sternoclavicular joint. (Click here and here for other myth busting)

MYTH # 1

Many believe that less relative motion equals less significance in the bigger picture of movement. That might be true in some contexts but definitely wrong as a blanket statement.

Part of the reason this joint gets ignored lies in the paucity of (recent) research.

In fact, the most frequently cited study on SC joint movement was published almost 60 years ago by Inman et al.(1)

Hitherto, we need more research on this joint

The truth is that the SC joint moves quite a bit (in concert with the AC joint). This coordination is what leads to larger movements of the glenohumeral joint and the scapula and on the thorax.

SC joint osteokinematics are described via the resulting motion of the clavicle.

  • Elevation/Depression - in the frontal plane

  • Protraction/Retraction – in a horizontal plane

  • Posterior Rotation – in a (near sagittal plane)

image from Ludewig et al (2)

In their in-vivo study of the 3D kinematics of the SC joint, Ludewig et al demonstrated that during maximum arm elevation the SC joint accounts for

  • 6 degrees of elevation

  • 16 degrees of retraction

  • 31 degrees of posterior rotation (2)

In addition to lack of information there is also conflicting information.

MYTH # 2

Maybe not quite 50 shades, but there is a decent amount of “grey” when it comes to the known arthrokinematics of this joint.

As a movement practitioner, if movement potential is lacking you want to find out how and why. Sometimes it is a “joint” problem. To test joint play one must have an understanding of arthrokinematics. At least that is what we’ve all been taught.

With regards to arthrokinematics of the SC joint most agree on the intricacies of clavicular elevation/depression and posterior rotation.

During elevation of the clavicle the articular surface ROLLS superiorly and SLIDES INFERIORLY on the sternum. The opposite happens with clavicular depression

image from Neumann (3)

As the clavicle posteriorly rotates, the clavicle’s sternal end spins relative to the lateral surface of the articular disc.

When it comes to the mechanics of protraction and retraction things are less clear.

Kinesiology expert Don Neumann describes the joint mechanics of protraction and retraction as such (3):

Protraction: The clavicle both rolls and slides ANTERIORLY

Retraction: The clavicle both rolls and slides POSTERIORLY

When researching for this post, I discovered there are conflicting views on the arthrokinematics of the SC joint for protraction/retraction. I’d say sources were mixed, 50-50. I actually learned the opposite of Neumann’s description. (i.e., for protraction the clavicle will roll anterior but glide posteriorly)

Inconsistency can be confusing so I sought clarification by emailing shoulder expert Paula Ludewig, PT, PhD. The majority of kinematic research on SC joint, AC joint and scapula over the last 10 years bears her name.

Here is her response to my question:

Until we have more research data what do we do with uncertainty? Not evaluate joint play because there might not be a “NORMAL”?

These questions lead us to another grey zone – the rules (or principles) we are taught for manual therapy.


If there is arthrokinematic variability how do we assess this joint? And if we even consider manual therapy as an intervention, what rules apply?

I think the answer might lie in the debate over the concave-convex rule. Did you know it was even up for debate?

As a main tenant taught in manual therapy, the concave-convex rule can be more accurately described as a principle. In reality, it is more of a theory based on observations of how structure and function correlate. The concave-convex rule is intended to assist a practitioner in determining the direction of mobilizing glide.

The problem is multiple kinematic studies show the arthrokinematics described in the rule don’t always apply. Examples include radial head movement during supination at the proximal radial-ulnar joint (4), femoral translation during deep knee flexion (5) and humeral head translation during external rotation (6) (with adhesive capsulitis) and abduction.(7)

Sometimes Myths (Like Rules) Are Made For Breaking

Neumann tackles this topic in a 2012 editorial in the Journal of Orthopedic and Sports Physical Therapy.(8) He argues that the intention of the concave-convex rule is to provide a description of how a joint might roll and slide to optimize joint centration rather than a directive for manual therapy. With this in mind, one would still assess joint play (as part of a more comprehensive exam) and mobilize in the direction of restriction.

Neumann also brings up an important point when reflecting on the contradicting studies. Starting position matters, or simply stated, position matters.


Our (understandable) love affair with movement has lead to a neglect of static measures of position.

Movement is the behavior we consistently assess in the hope that we can manipulate its variables to enhance resiliency. There is more to the story. Static measures of position help us understand how the axial skeleton has self-organized with years of adaptations. They can explain why motion is limited at a joint and why other systems are responding in a particular way.

For the SC joint we can use the following to accrue information:

  • The clavicular resting position (relative to the horizontal plane)

  • The angle the clavicle makes with the plane of the scapula

We must remember two important things when we consider these metrics.

  • There is likely variability based on the influence of a number of factors.

  • These measures are made relative to something else, meaning they are influenced by and potentially affect something else.

The clavicular resting position:

  • Chaitow cites 25-30 degrees as “normal” (9)

  • Ludewig et al found the mean to be 19 degrees (+/- 5 degrees)- (2)

When considering movement at the SC joint we can use this position measure as a starting point for clavicular movement.

The clavicular resting position may be influenced by or affect the resting scapular position:

image from Kapandji (10)

The angle the clavicle makes with plane of the scapula, observed from a cranial to caudad perspective is another measure of relative position that can give us information about the SC joint.

image from Kapandji (10)

Several sources cite 60 degrees as normal and in terms of SC joint movement, should be considered when contemplating how the scapula and clavicle move together.

The picture below (of a melon and kitchen tongs) demonstrates how the shape of a thorax, narrow or wide A-P) might influence this angle both at rest and with movement.