Referred pain: why the spot that hurts is rarely the spot that needs treatment

When a muscle develops a trigger point, the pain you feel is usually not over the muscle itself. Travell and Simons documented this systematically for decades: the infraspinatus, buried under the shoulder blade at the back, sends its pain to the front of the shoulder and down the arm; the scalenes in the side of the neck imitate carpal tunnel symptoms in the hand; the soleus in the calf can refer as far as the jaw. The patient points where it hurts, and the source sits quietly somewhere else, often in a spot that does not hurt at all until it is pressed.

This is not a curiosity. It is the reason so many musculoskeletal complaints are treated at the wrong address. Rubbing, injecting or operating on the painful spot treats the echo, not the source. The classical charts — the referred pain patterns published in the trigger point manuals — exist precisely because these patterns are consistent enough across patients to be drawn.

For the terminology and interpretation used here, compare What are trigger points?; Primary vs secondary trigger points; How to read referred pain maps. These guides distinguish the definition of a trigger point, its classification and the limits of a referred-pain map.

Referred pain is not unique to trigger points — the nervous system has always been poor at localising deep structures — but trigger point research has given it a measurable basis. Shah's microdialysis work showed that the active trigger point sits in a bath of inflammatory mediators and sensitising substances, a local chemistry capable of lowering the threshold of nearby nerve endings. Ge and others showed that the referred zone itself becomes sensitised: pressure applied over the referred area hurts more than the same pressure in control subjects, even though nothing is structurally wrong there.

The current explanation is convergence and central sensitisation: sensory fibres from the muscle and from the referred region funnel onto the same second-order neurons in the spinal cord, and a persistently irritated input makes those neurons respond to both. Gerwin's reviews of the integrated hypothesis place this within a broader picture in which the taut band, the local chemistry and the spinal processing reinforce one another. Sceptical reviews such as Quintner's accept the phenomenon of referred pain while disputing how much of it the trigger point model explains — a useful reminder that the map is a hypothesis to test, not a diagnosis to assume.

The referred pattern is a starting point, not a verdict. The clinical test that carries weight is recognition: pressing the suspected trigger point reproduces the patient's familiar pain — the pain they came in with, not just a new soreness. That is why the manuals insist on asking "is this your pain?" rather than "does this hurt?". A tender spot that produces an unfamiliar ache is just a tender spot; most people have several.

The map also has known failure modes. Referred patterns vary between individuals, more for some muscles than others; the reliability studies on palpation show that even trained examiners agree only moderately on exact point locations, which is one reason the honest protocol is to confirm with the patient's own recognition. And referral is not one-way proof: pain in the front of the shoulder can come from the infraspinatus, but also from the deltoid, the supraspinatus or the neck. The pattern narrows the search; it does not close it.

The practical rule follows directly: treat the source, not the sore spot. If the front of your shoulder hurts, pressing the front of your shoulder is unlikely to change much; the muscle pages on this site exist to redirect that search. Start from the pain pattern, work back to the muscles whose referral zones cover it, and confirm each one by pressing until you find the spot that reproduces your own pain. That recognition — not tenderness alone — is your green light.

Two cautions keep the rule safe. First, referred pain explains muscular pain, not all pain: constant pain that ignores position and load, pain with numbness following a clear nerve territory, or pain with general symptoms like fever belongs to a different workup. Second, when several muscles refer into the same area — which is the norm, not the exception — expect to treat more than one, in the order the symptom pages suggest, and judge the result over days rather than minutes.