with contributions by Keith Wittenstein. Special thanks to Sarah Court, Dinneen Viggiano and Trina Altman for editing and feedback
Last time, I discussed the dissonance between scapuloclaviculohumeral rhythm and the common cue of scapular depression during shoulder flexion.
Instead of attempting to draw the shoulders down while simultaneously trying to flex the shoulders, consider ways to work and cue upward rotation of the scapula. A cue such as “Lift your outer shoulder blade up as you move your inner shoulder blade down” will facilitate more ease of movement and a safer position for the soft tissues of the shoulder Admittedly, this cue is far more nuanced than cues that take the whole shoulder blade in one direction, like “pull your shoulder blade down” or “lift your shoulder blade up”. However, if taught verbally – but then also reinforced tactilely by feeling the shoulder blade and its different angles and borders, and visually by seeing the shoulder blade upwardly rotate in a demonstration – can work to help students find and engage the muscles that upwardly rotate their shoulder blades to gain better command of this movement. Upward rotation makes it so the shoulder blade can push the humerus into the overhead position via its connection to the socket, or glenoid fossa. More on the scapula as a ‘pusher’ of the humerus rather than a ‘puller’ later!
The last need-to-know shoulder joint player is the scapulothoracic joint. It functions as the slide and glide interface between the scapula and the rib cage. It is the interface at which the scapula can do its action of upward rotation, or spin like a turntable, when the arm goes overhead. This joint is purely functional in that it does not have a joint capsule surrounding the articulating surfaces of its bones, as opposed to the other joints listed above. However, many powerful muscles act on this joint making it a biomechanical nexus of shoulder mobility and stability. We will explore one of these muscles in detail in later blog posts.
If it weren’t for all of these joints, the AC joint, the SC joint and the scapulothoracic joint, the humerus would move a measly 30-60 degrees forward or out to the side from the glenohumeral joint alone – that’s well below shoulder level – before coming to a screeching halt. This is because its glenoid fossa (that’s the shoulder socket) would not be able to progress into the upward-facing position that it needs to be in to continue cupping the spherical head of the humerus in the overhead position.
In other words, the humerus would have to dislocate to continue its trajectory upward (not a humorous thought)! Luckily this extreme example is really only to help you visualize the function of upward rotation of the scapula, and not something that actually happens thanks to the exquisitely designed co-movement between the scapula, clavicle and humerus. This co-movement is probably best described by the term scapuloclaviculohumeral rhythm (say that ten times really fast!), coined by the anatomist Joseph Muscolino. This term is not only fun to say, but also helpful to understand shoulder movement by reminding us that there are three bones involved in shoulder movement, the scapula, the clavicle and the humerus. The following video illustrates this co-movement and refers to the movement as ‘shoulder kinematics’.
In the video, notice specifically how, along with flexion of the humerus (upward reach of the arm), the AC joint – where the clavicle and scapula connect – must also move upward toward the head. Specifically this co-movement, or rhythm of clavicular elevation and scapular upward rotation is what permits the humerus to move overhead. Quite plainly, you’re best to go with this rhythm, not against it.
Now, you feel the beat!
Feel your own rhythm by placing your right hand’s middle and index fingers on the end of your left collar bone. Press down and rub around a little on the end of your collar bone and you might feel a Frankenstein-type bump. That’s where your collar bone articulates at the AC joint. Now raise your arm overhead. The end of your collarbone, or your AC joint, lifts upward along with your arm. That is the result elevation of our collarbone and upward rotation of your shoulder blade.
Keep tuning in this month for the rest of this series, Uplifting News for Depressed Shoulders!