How dry needling works

One of the most common questions I’m asked during a consult is ‘how does dry needling work?’

For those of you who haven’t tried dry needling before, it involves the use of a sterile, single-use, fine filament needle, inserted into skin and muscle to resolve pain and tension. 

The needles can be left in-situ at various locations for several minutes at a time. They may also be used to elicit a local twitch response (LTR) by moving the needle around within the muscle.

Dry needling is used to resolve the presence of myofascial trigger points - a hyperirritable contraction knot, present within a taut band of muscle fibre. Usually, these are large enough to feel with your own fingertips. 

To understand how these develop, I’ll explain a little bit about how muscles contract.

The physiology of muscle contraction

More than 60 years have passed since the discovery that muscle contraction results from the relative sliding of thick (myosin) and thin (actin) parallel filaments. 

This sliding occurs because of the cyclic attachment and detachment of myosin heads which extend from the myosin toward the actin filaments that surround it. This can be likened to the action of an oar extending into the water to push a boat along the surface. 

Actin and myosin are arranged into functional units called sarcomeres. When these filaments slide along one another, it causes the sarcomeres ends to squeeze together and for the entire muscle length to shorten (contract). 

An individual muscle fibre can contain up to 100,000 sarcomeres in sequence (a muscle fibre will often run the entire length of a muscle).

Muscle fibres are arranged into groups known as motor units, each of which has a single nerve supply called a motor neuron. 

Not all motor units within a muscle contract together, or in the same way. It largely depends on what is required at that time. 

This separation into motor units also ensures that if a part of the muscle is damaged, there remains healthy muscle tissue to continue carrying out the function of the muscle. 

When a motor neuron receives a message from the brain telling the muscle to contract, it will trigger a sequence of events that causes the sarcomeres within those muscle fibres to begin forming cross bridges and shortening.

Actin and myosin are filaments that make up a sarcomere, the functional unit of a muscle. These filaments link, and slide along each other when a muscle contracts.

Visual representation of myofascial trigger points formed within a muscle in the neck.

What are trigger points?

The layman’s term for a myofascial trigger point is a ‘knot’ in the muscle. They feel like a little nodule within the muscle and often elicit a lot of pain. 

The right kind of pressure, however (i.e. massage), can be quite relieving. 

A key characteristic of an active trigger point is that when pressure is applied, it is not only tender but also causes a predictable pattern of referred pain. 

Muscle trigger points tend to form in the centre of a muscle belly, where the motor neurons synapse (connect) with the muscle fibres. 

While there isn’t a consensus on why trigger points form, it is likely caused by a fault in the contraction signalling pathway, resulting in a sustained contraction in a small region of the muscle. This change appears to be linked to the excessive release of the chemical acetylcholine.

There will also be increased tension in the muscle fibre on either side of the knot, all of which contributes to pain and dysfunction. Several myofascial trigger points may form within a muscle, so too around the entire body.

Touching on pain mechanisms

There are also several theories as to why trigger points cause pain. 

Recalling the discussion around pain mechanisms in a previous post, it is most likely the primary driver of pain is a nociceptive mechanism.

Local inflammation and mechanical stimuli caused by the trigger point stimulate pain receptors to relay a pain message to our brain. This may occur at rest, or through provocation with movement or external pressure.

However, due to the distinguishing feature of referred pain, and the often-widespread presence of multiple persistent trigger points, it is likely that neuropathic and dysfunctional pain mechanisms are also in play.

How does dry needling help?

So, how does inserting a needle into one of these contraction knots cause it to relax or become less painful?

Again, some theories exist but little is definitively known. Some of these things are hard to study at a microscopic level because they only occur in a live muscle. So, we only have a zoomed-out perspective.

Dry needling seems to involve the part of our brain involved in emotional responses (limbic system) and a part of our nervous system involved in controlling pain (descending inhibitory pathway).

Studies show that dry needling of a few trigger points not only reduces nociceptive input from the treated trigger points, but reduces overall widespread pain and sensitivity. This makes it a useful tool in the treatment of ‘dysfunctional pain’ conditions such as fibromyalgia.

One effect of dry needling is that it causes a local twitch response. If you’ve had dry needling therapy you will likely be familiar with this. 

A local twitch response is an involuntary contraction of the muscle driven by a spinal cord reflex that the dry needling prompts. 

Triggering the local twitch response has been shown to reduce the concentration of nociceptive substances in the chemical environment near the myofascial trigger point.

The needle may also affect muscle regeneration by causing a small focal lesion which triggers repair of the damaged muscle fibres. This effect would take place 7-10 days following the needling rather than immediately.

Another potential mechanism is a localised stretching of the muscle architecture which may allow sarcomeres to return to their normal resting length.

Dry needling to reduce pain

Regardless of the mechanism, studies that look at the effect of dry needling on pain generally support its use.

While it is not fully understood, it’s becoming increasingly clear that dry needling can be an effective means of treating pain, through its inhibitory effect on the messaging of pain from tissues in the body to the brain, and by stimulating the release of pain-relieving chemicals in the brain.

Dry needling can restore muscle strength and flexibility when it has been impaired by persistent trigger points. It is a treatment option I find highly effective when treating my patients.