Mirror therapy for chronic pain.

How does mirror therapy work?

To produce pain, the brain has to decide that a body part is under threat. It makes that decision using every source of information available — signals from the tissue, yes, but also vision, memory, expectation, and context. Mirror therapy exploits the fact that vision is unusually persuasive.

When you watch a reflection of your healthy hand opening and closing where your painful hand should be, the visual system delivers unambiguous evidence: that limb is moving freely, and nothing bad is happening. That evidence conflicts with the brain's existing prediction, and the conflict is what creates room for the prediction to change.

What's happening in the brain

Watching a limb move activates somatosensory and premotor circuitry associated with that limb — much of the same machinery involved in moving it yourself. In chronic pain and after amputation, the cortical representation of the affected body part is often distorted; mirror feedback appears to help renormalize it. Studies of illusion-based mirror setups during functional imaging show measurable changes in brain activation, which is why the mechanism is usually described as cortical reorganisation rather than distraction.

What conditions does mirror therapy treat?

Phantom limb pain

This is where mirror therapy began. Ramachandran's insight was that phantom pain often involves a limb that feels frozen or clenched in a painful position, and that the brain has no visual evidence to contradict it. A mirror reflecting the intact limb restores the missing feedback — the phantom is seen to move, and for many people the pain eases. See our page on phantom limb pain.

Complex regional pain syndrome

CRPS features severe pain, allodynia, and often a distorted sense of the affected limb's size or position. Mirror therapy is standardly used as the final stage of graded motor imagery, and the GMI protocol has randomized evidence in CRPS. See complex regional pain syndrome.

Stroke rehabilitation

Mirror therapy is widely used to improve motor function in a hemiparetic arm, and to address CRPS type 1 that develops after stroke. It is generally used alongside conventional rehabilitation rather than instead of it.

Chronic limb and joint pain

Evidence here is younger and thinner than in the conditions above, but the rationale carries over: where movement is limited by anticipated pain rather than by structure, visual feedback offers a way to test the limit without triggering it. Karuna's mechanistic work sits in this territory.

What has Karuna's research found about mirror visual feedback?

Karuna Labs ran a small preliminary mechanistic study — approved by an institutional review board — in 17 adults with chronic shoulder pain, to test whether mirror visual feedback delivered in virtual reality could influence pain-free range of motion.

Participants wore a VR headset and moved each arm while a virtual avatar mirrored their movement. In one condition the avatar matched the arm they were actually moving; in the other, the movement of the unaffected arm was displayed as though it were the painful arm.

The result was the one that makes the mechanism visible. When people moved their healthy arm but saw the painful side moving, their pain-free range of motion decreased — significantly so for shoulder flexion and scaption. The healthy limb had not changed. Only the belief about which limb was moving had changed.

This was single-session work in a small sample, and it was designed to probe mechanism rather than to demonstrate a treatment effect. What it establishes is that mirror visual feedback in VR reaches self-perceived movement limits — the exact target of graded exposure work. It also underpins the design of our virtual reality training, where the same principle is used deliberately, in the helpful direction.

How do you do mirror therapy?

The setup is simple enough to do at home, though it's worth having a clinician guide the first sessions — particularly with CRPS, where starting too aggressively can provoke a flare.

1. Sit at a table with a mirror positioned vertically along your midline, reflective side facing your unaffected limb.
2. Place the affected limb behind the mirror, out of sight. Remove watches and jewellery from both sides.
3. Position yourself so the reflection appears where the affected limb would be.
4. Move the unaffected limb slowly and watch the reflection, allowing yourself to accept it as the affected limb.
5. Start with 5–10 minutes and simple movements. Build toward 20–30 minutes and more complex ones.
6. Stop if pain increases sharply, or if you feel disoriented or distressed — then restart shorter and slower next time.

Consistency matters more than duration. Most protocols use daily or near-daily sessions over several weeks, because what you're doing is accumulating evidence, and evidence accumulates through repetition.

What are the limits of mirror therapy — and how does VR extend it?

Mirror therapy has one structural constraint that no amount of technique can solve: it requires a body part that comes in a pair. A mirror can substitute a left hand for a right hand. It can do nothing for the lower back, the neck, the midline — or for someone whose pain affects both sides.

Since chronic low back pain is the single largest chronic pain problem there is, that limitation excludes an enormous number of people from the technique.

What virtual reality changes

In VR, the person occupies a virtual body from a first-person perspective. The system does not need to reflect anything, because it can simply render what the body appears to be doing. That removes the lateralization requirement and adds capabilities a mirror does not have:

• Non-lateralized regions. Spine, neck, and trunk can be addressed, because no mirrored pair is needed.
• Augmentation. Movement can be visually amplified or reduced relative to actual motion — so a small real movement can be seen as a larger one, and vice versa.
• Measurement. Joint angles are tracked continuously, so range of motion can be graded and paced to what a person can currently do.
• Graded difficulty. Exercises adjust to current capability, which keeps exposure within tolerance and reduces flare-ups.

This is the reasoning behind Karuna's approach: take the mechanism that makes mirror therapy work, and remove the constraint that limits where it can be applied. More on that in VR pain management and how the programme works.