Why Pain Can Linger After an Injury Heals: Central Sensitization

Pain can linger after an injury heals because the nervous system can stay on high alert. After weeks or months of pain, the spinal cord and brain can become more reactive, so ordinary pressure or movement is read as a threat. This is called central sensitization. The pain is real, and a sensitized nervous system can calm down.

When healing and pain do not match

Most injuries follow a familiar path. It hurts, it heals, and the pain fades. But for some people the scan looks fine and the tissue has done its job, and the pain stays. Sometimes it spreads to new areas. Light touch or the waistband of your pants can hurt. A bad night of sleep or a stressful week sends it up.

That mismatch is confusing. Sometimes something was missed, and that is always worth checking. Often, though, the nervous system itself has changed.

What central sensitization means

Pain is not a direct readout of tissue damage. Nerves in the body send signals to the spinal cord, and the spinal cord and brain decide how loud those signals feel. The International Association for the Study of Pain defines central sensitization as increased responsiveness of the pain-processing nerve cells in the spinal cord and brain to their normal input, or to input that would usually be too weak to register.

In plain words, the volume has been turned up. A smoke alarm that goes off every time you make toast is a fair picture. The alarm works, but it is set too sensitive.

A real, physical change

A sensitized nervous system is a real, physical change in how pain signals are processed. The same international pain association says a person's report of pain should be respected, and that pain and the signals from tissue are different things. In fibromyalgia, a condition of widespread pain and tenderness, the NIH notes that brain imaging and other research have found altered signaling in the pathways that carry pain. My fibromyalgia page explains how I approach it.

Sensitization also often sits alongside a real tissue problem. Part of the original injury may still be there, so I look for both.

What keeps the volume turned up

• Poor sleep. A 2019 study in the Journal of Neuroscience found that sleep deprivation lowered pain thresholds and amplified pain responses in the brain's sensing regions. In everyday life, even small night to night changes in sleep quality predicted the next day's pain.
• Stress. Stress keeps the nervous system on alert.
• Guarding. Bracing, protecting a sore area and avoiding movement out of fear can keep the system sensitized.
• Leftover tissue drivers. Trigger points in muscle, a stiff joint or an irritated nerve can keep feeding signals into a system that is already sensitive.

What helps calm it

The goal is to lower the volume gently while treating any tissue source that is still feeding it. The CDC's 2022 pain guideline lists non-drug approaches for fibromyalgia, a condition in which sensitization is common, including exercise therapy, cognitive behavioral therapy, mindfulness, tai chi, acupuncture and multidisciplinary rehabilitation. The benefits in that research are small to moderate, so most people do best with several working together.

In practice, that means movement that builds slowly, sleep treated as part of care, and pacing so a good day does not turn into a flare. In my experience, understanding what is happening also takes some of the fear out of a flare.

The first visit runs 60 to 75 minutes, and the exam is gentle and at your pace. I use gentle acupuncture and neuro-functional acupuncture aimed at calming the nervous system as a whole, and dry needling in small, careful doses for trigger points that are still feeding the pain. Neuro-functional acupuncture is built on neuroscience and evidence-based practice. Unlike regular electroacupuncture, the needles and gentle electrical stimulation are mapped to the specific nerves involved. It works in three ways. It neurorehabilitates, helping irritated tissues and nerve receptors recover. It neuromodulates, shifting the body's own pain-relieving chemistry. It neuroregulates, calming the nerve signals and circuits that keep pain going after the injury has healed. I bring more than 18 years of clinical experience with dry needling for musculoskeletal pain, and I coordinate with your physician, pain specialist or therapist. If you have already tried many treatments, my chronic and refractory pain page explains how I approach that.

If you are not sure what is causing your pain, try the My Symptoms tool.