What are muscle "knots" (often in the back or neck) actually made of? How do they happen and how can they be prevented? Are they harmful and should they be treated?

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Surprisingly, no one knows definitively what muscle knots are made of — and some researchers question whether they even exist at all.

Many experts believe that the knots, often referred to as myofascial trigger points, are “specific areas of contraction within the muscle fiber,” said Rob Grieve, a senior lecturer in physiotherapy at the University of the West of England in Bristol, England, who has studied the phenomenon.

The knots seem to develop when a muscle tenses repeatedly and “are normally not caused by a specific, traumatic event,” he said, “but by muscle overuse or faulty biomechanics.” (This is also known as slouching.)

It is thought that these small bits of hyper-tensed muscle cause discomfort and pain by “blocking some of the normal blood flow to the affected tissue,” said Jan Dommerholt, a physical therapist in Bethesda, Md., who studies and treats muscle knots.

But writing in the March issue of Rheumatology, scientists from Australia and the United States pointed out that muscle knots rarely show up on scans, leaving researchers with “no scientific basis” for believing that knotted muscle fibers make us sore. Instead, the researchers contend, the soreness is likely neural, involving the brain and irritated nerve endings.

Regardless of the possible cause, most therapists feel that the best treatment for purported muscle knots is to pummel them. Vigorously massage the sore spot with hands, Dr. Grieve said, or use a small, hard ball (such as those used for lacrosse) or a foam roller.

If the soreness persists, Dr. Dommerholt said, consult a doctor or physical therapist, who may suggest acupuncture or injections of anesthetics, both of which have shown some benefit. Injecting an empty needle into the sore spot, a treatment called dry needling, also often reduces pain, he said, although whether by breaking up knotted tissue, calming inflamed nerves or prompting a robust placebo effect, no one knows.