Do subscapularis trigger points (muscle knots) cause frozen shoulder?

Drs. Janet Travell and David Simons are famous for the “big red books,” their seminal muscle pain text in two volumes. Those texts suggest that the subscapularis muscle of the shoulder may be a major factor in frozen shoulder (adhesive capsulitis).

It is the only detailed case for such a relationship that I know of. Travell and Simons devote most of a page to it (vol 1, pp 605–6). They assert that “many clinicians agree that subscapularis trigger points can be responsible for the symptoms of ‘frozen shoulder’,” but they responsibly acknowledge that “competent research substantiation is essential.”

It really is.

Their views on the matter are probably the major reason for the popularity of subscapularis treatment amongst massage therapists. This muscle is often touted as a bit of secret sauce, something that only wiser massage therapists know about. You work the subscapularis via the armpit — nothing like a good armpit rub! — and so it has the mystique of treatments in the “wouldn’t go there without a good reason” category.

Subscapularis massage is often touted as a bit of secret sauce, something that only wiser massage therapists know about.

Good ol’ “subscap”: subscapular or subscapularis?

And where there’s mystique, there’s confusion. Beware of abbreviations in anatomy. This is a classic example, and an interesting tangent, mostly for professional readers, though a few patients with frozen shoulder might want to slog through it. Or skip to the next section.

The “pros” sometimes don’t understand the difference between subscapularis and subscapular, which is often made worse by the ambiguous abbreviation subscap, which could mean either or both. And it matters! To some therapists, this will seem absurd, the difference obvious: while all subscapularis massage is subscapular (because that muscle is under the scapula), not all subscapular massage is subscapularis (because there are other muscles under the scapula). But I have encountered the confusion both in school and in the wild.

Some back muscles are under the shoulder blade: they are subscapular, but they are not the subscapularis muscle.

A therapist may claim to treat frozen shoulder by doing “subscap” work, but then veer away from the subscapularis treatment intended by Travell and Simons, instead choosing to pull the shoulder blade away from the spine and pressing firmly on the revealed back muscles — which are indeed subscapular, but definitely not subscapularis. There is not even a theory that the subscapular muscles of the back are a key factor in frozen shoulder. At best, they are victims of a troubled area, in need of soothing, but far from critical to a cure.

Buyer beware, eh?

The theory of the connection between trigger points and frozen shoulder

In a nutshell, Travell and Simons hypothesize that subscapularis dysfunction is “quite likely” a cause of frozen shoulder because a cranky subscapularis muscle may cause adhesions within the subscapular bursa (a fluid-filled sack that reduces the friction of the subscapularis tendon as it slides of the surface of the shoulder joint). This bursa is known to be one of the main spots where the freezing of frozen shoulder occurs.

It’s a perfectly reasonable hypothesis, entirely worthy of study. But it’s just a hypothesis. And I see a major problem with it — don’t I always?

The theory requires enesopathy, irritation of the subscapularis tendon, to be the power source for adhesions in the bursa: irritation of the tendon leading to inflammation of the bursa beside it, ultimately causing the bursa to seize up. That’s a lot of tightness due to subscapularis trigger points, and a lot of inflammation for a situation that does not involve any actual tendinitis or early acute symptoms. Basically Travell and Simons are saying that adhesive capsulitis may be caused by trigger points and enesopathy nasty enough to seize up your bursa … but which you don’t notice until it’s already half happened.

Bear in mind that enesopathy is hardly uncommon. At any given time, most people probably have at least a few enesopathic tendons scattered around their bodies. It’s not tendinitis, just irritation and sensitivity of “yanked on” tendons. And nearly all tendons are associated with bursae. And yet bursae do not, as a general rule, seize up the way they do in the case of frozen shoulder. If they did, you’d expect to see frozen hips, frozen knees and frozen elbows. But frozen shoulder is the only somewhat common condition where a joint capsule really seizes up.

Frozen shoulder sneaks up you. You are aware of gradually increasing pain and stiffness in the shoulder. By the time you notice you can’t do up your bra or reach the high kitchen shelf, you’ve already lost the extremes of your range. By the time your shoulder becomes annoyingly painful, the condition is already well underway.

The major logical problem with Travell and Simons’ hypothesis is that any trigger point trouble in the subscapularis bad enough to nearly destroy the joint should also be extremely uncomfortable and obviously limiting long, long before the joint capsule actually becomes adhered. Remember that bad trigger points are bad — quite capable of causing extremely severe pain, weakness and tightness. So I counter-hypothesize that the subscapularis muscle would have to obviously be in trouble long before the joint capsule is actually in danger.

It’s not about right or wrong, it’s about overconfidence

The concerns I’ve raised are not a deal-breaker for the theory. The theory may well still be correct. It is completely plausible that there is something uniquely vulnerable about the shoulder joint, and I would love to see a researcher tackle this.

But the logical problem I’ve pointed out is absolutely a confidence breaker. Remember that massage therapists don’t just do subscapularis massage for frozen shoulder: they tend to do it reflexively, overconfident that it “works” without even being clear about how it works. It’s in the big red books, right? So it must work!

And that’s assuming that they even know the provenance of the idea. Or that they can distinguish between subscapularis and subscapular massage!

Travell and Simons have offered a good idea. But therapists need to bear in mind that it’s only an idea, which could just as easily be wrong as right, for the reasons I’ve laid out here. And frozen shoulder patients need to be savvy and remember: when a massage therapists pokes you in the armpit, it’s not even remotely a proven treatment for frozen shoulder.