Infraspinatus Trigger-Point Syndrome

By Perry Nickelston, DC, FMS, SFMA

Numerous musculoskeletal pain syndromes and movement dysfunctions can be related to trigger points in the infraspinatus muscle. Due to the inhibitory nature of chronic trigger points, there is eventual decreased muscle activation and tone causing poor stability in functional movement patterns.

The infraspinatus is a nasty culprit in almost everything. You can count on this muscle being a factor in every shoulder dysfunction, pain or injury, but there are even more body regions that are affected by this trigger point when the body compensates for the lack of motor control and stability.

One of the four rotator cuff stabilizers of the shoulder, the infraspinatus is prone to active, latent and satellite trigger points. It attaches medially to the infraspinous fossa of the scapula and laterally to the middle facet of the greater tubercle of the humerus. It originates by fleshy fibers from its medial two-thirds and by tendinous fibers from the ridges on its surface. The fibers converge to a tendon that glides over the lateral border of the spine of the scapula and, passing across the posterior part of the capsule of the shoulder joint, is inserted into the middle impression on the greater tubercle of the humerus. It is an external (lateral) rotator of the glenohumeral joint and adductor of the arm. The infraspinatus and teres minor rotate the head of the humerus outward (external or lateral rotation); they also assist in moving the arm backward (extension of the glenohumeral joint). However, the infraspinatus is the major external rotator.

Common sense dictates that muscles need to contract and relax for movement to occur. Without this action system, we would be immobile. The problem is in how much and how well these muscle contractions occur. When muscles are affected with a trigger point, they become inherently tighter; sort of like tying a knot in a rope naturally shortens its original length. The presence of the knot and ensuing stiffness ultimately cause a loss in range of motion. This is exactly what happens to a muscle.

All of the origin and insertion points become negatively influenced and joints lose proper mobility. Inherently, the body attempts to compensate for this abnormal motion, causing other areas to become tight and restricted. The first inclination is to stretch out the tightness in an attempt to gain flexibility because it feels good (temporarily). But it never seems to last and sometimes even feels worse afterward.

A muscle is literally numerous individual bands linked together to form a single functioning unit. When you tighten these bands, the body reacts in an attempt to protect itself from injury. When you keep stretching and pulling this tightness, the nervous system eventually sends a signal to that muscle to deactivate (decrease tone and contraction) in an attempt to prevent damage. As a result of this signal, the muscle relaxes too much and it becomes weaker and less stable. That is, until your body attempts to find that stability somewhere else and adds tightness to another region. Muscles don't function in isolation, so there are always compensations patterns that must be assessed.

The infraspinatus may have several trigger points within the muscle fibers. Each point refers pain to different zones of the body. If you assess the entire muscle when you render therapy, you will have success alleviating all referral symptoms. Referred pain patterns from infraspinatus trigger points are associated with anterior shoulder pain, biceps pain, mid-scapular pain, and even tingling and numbness into the forearm and hand. The pain can be sharp, dull, burning, aching, tingling and numb. It knows no limits in its pain patterns, so suspect it with everything.

I evaluate the infraspinatus on every patient regardless of their presenting complaint. I have yet to find a patient who did not have an issue with an underlying trigger point and/or asymmetry between left and right infraspinatus muscles. So the takeaway here is simple: Every patient should have the infraspinatus muscle evaluated. Never overlook it!

There are many scenarios that can happen in regards to dysfunctional movement patterns when the infraspinatus no longer functions at 100 percent capacity. Knotted muscles will begin to deactivate and lose tone. Therefore, they can no longer perform their role of stabilization and motor control efficiently. When the infraspinatus starts to lose tone, the shoulder will then begin to internally rotate. This is one of the primary components to the typical rounding of the shoulders associated with the upper crossed syndrome paradigm developed by Vladimir Janda.

What occurs next is a cascade of dysfunctional movement. The shoulder rounds forward and the chest tightens, and the shoulder blade rotates out, putting extra contraction on the mid-back muscles. They start to fatigue and the arm drifts forward in the socket, causing anterior compression on the humeral head. The shoulder hikes up toward the ear as the trapezius muscles tighten, acromio-clavicular joint mechanics are altered, and spinal vertebrae stability becomes a factor. All of these compensatory tight muscles can develop their own latent and satellite trigger points. Some may argue that tightness in the pectoral muscles (pec major/minor) were the initial trigger points and the infraspinatus reacted to that; well, that could very well be true. But how do you think we would address this situation, regardless of what caused the initial onset? You treat both.

Trigger points are not to be overlooked. They are not simply muscle knots that cause pain. They cause serious movement dysfunction and can be excruciatingly painful. In order to re-develop this muscle and tone it again you must remove the knots first. You can't tone a muscle that has trigger points.

How do you get rid of the trigger points? My preferred way is with deep-tissue laser therapy to help improve the cellular chemical damage caused by the trigger point. The clinical choice of therapy is up to you as the treating physician. Treatment choices are methods, and there are numerous ones to choose from depending on your area of expertise. However the primary importance is to understand the baseline principles of how they cause dysfunction. Once you know these principles, you are on the right track.