BMJ Group Medical Reference
Physiotherapists sometimes treat a painful shoulder with a beam of light known as a laser.
Several small studies looked at whether having laser treatment reduced shoulder pain.   The laser treatment was usually given two or three times a week for five minutes or 10 minutes.
In most of the studies, people who had laser treatment felt less pain. But in one study, having laser treatment for two months made no difference to people's shoulder pain. 
Resesarchers have also compared laser treatment with ultrasound. One study found that people who had laser treatment had less pain after two weeks than those who had ultrasound. However, there wasn't much difference between the groups in how much they could move their shoulder and how they rated their symptoms overall. 
We don't know if laser treatment can have side effects. The research doesn't tell us enough to be certain.
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