The subscapularis (aka subscap, to rhyme with hubcap) is a triangular muscle which sits between the ribs and the shoulder blade (scapula) — its name meaning literally “below the scapula”. With its base covering the entire of the inside edge of the scapula, it narrows to a tendon which attaches to the inner part of the humerus (upper arm bone) and the shoulder joint capsule. Its role is to twist the arm inwards (place your hand on your stomach and try to push through to your spine: you’re using your subscap) and to pull the humerus forward and down when your arm is raised, thus preventing your shoulder from dislocating.
It’s one of the four muscles that make up the rotator cuff, (the others being supraspinatus, infraspinatus and teres minor, if you’re interested!) but far less frequently torn than the more vulnerable supraspinatus and infraspinatus. Probably because of this, it’s a muscle that’s often ignored by therapists when treating sore necks and shoulders, but in my view that’s a mistake. Good subscap function is essential to good neck and shoulder function, and I have a few theories as to why this is the case.
One theory is the effect that subscap has on the ribs. As I’ve mentioned, subscap sits between the ribs and the scapula. Normal shoulder movement depends on the scapula being able to glide freely over the ribs. When muscles are sore, they tend to tighten up and develop trigger points — isolated areas of muscle spasm; and subscap is no exception. It’s my belief that tightness and/or trigger points in subscap can be partly responsible for dysfunctional movement of the scapula over the ribs. This in turn places excessive strain on the rib and shoulder joints, leading to pain in the upper back, neck and/or shoulder.
Subscapularis — deep in the armpit
I believe that another problem with subscap trigger points is the effect these have on blood flow and nerves. I suspect that when a muscle is tight, its spasmed fibres affect not only each other, but also other local structures such as blood vessels and nerves. In the case of subscap, this could — theoretically — affect the axillary (armpit) artery and the ulnar branch of the brachial plexus — the nerve that goes down to the inside of the elbow and the ring and little fingers. It’s certainly noticeable that patients often comment that they feel odd sensations in these areas, as I release their tight subscaps; or that once I’ve finished, they feel a rush of heat to the area (increased blood flow?)
Releasing the subscap is pretty tricky to do on your own. I often use my heels to release subscap in my patients — most therapists use their fists or fingers, but it’s hard to do that without jabbing your patient and causing more discomfort than necessary. If I have to release your subscap, I’ll ask you to lie on your back with your hand behind your head. This brings the edge of your scapula out to the side of your body, and I can then fit my heel between the edge of your scapula and your ribs, and use my bodyweight to stretch and massage the subscap, gently and rhythmically until the spasm subsides.
Not only does this tend to release the subscap spasm, it also frequently seems to relieve neck pain and increase in rotation at the neck, which is a great side effect. I’m not sure whether this is also due to better rib mobility, or whether there is some sort of chain reaction going on whereby the subscap release causes a release in the levator scapulae — any bright ideas gratefully accepted!
After I’ve released your subscap, I’ll show you how to stretch it yourself, using a chair, Swiss ball or yoga brick, so that you can maintain the improvement at home.
See my page on shoulder pain treatment.