Tendinopathy is an inflammatory process that occurs in and around the tendon when both are affected by a certain injury. In the case of the supraspinatus muscle it is one of the most frequent causes of shoulder pain. To test the efficacy of laser treatment in reducing shoulder pain caused by supraspinatus muscle tendinopathy. A randomized controlled clinical trial was carried out in which a physiotherapy intervention was performed using therapeutic laser for four weeks, to observe the influence on the pain generated by supraspinatus muscle tendinopathy in the shoulder. A sample of 82 patients was recruited and randomly divided into two groups: experimental group and control group. Laser therapy was applied to the first group and to the second group it was applied as a placebo

Inclusion Criteria:

• Age 30-65 years.
• Present a 3 or higher on the visual analogue scale in the shoulder.
• Adequate cognitive capacity for comprehension.
• Tendinopathy of the rotator cuff confirmed by ultrasound at the study center, either by inflammation of the tendon, presence of hypoechoic zones, calcification, fibrillar disorganization and/or neovascularization in the supraspinatus muscle.
• Pain in the proximal side of the arm that is aggravated by abduction.

Exclusion Criteria:

• Laser-specific contraindications (e.g., tumors, presence of pacemaker or defibrillator, pregnancy, etc.).
• History of glenohumeral fracture and rheumatoid arthritis.
• Rheumatic, neurological or structural polymyalgia affecting the joint.
• Previous surgeries.
• Pregnant or breastfeeding women.
• Taking anticoagulants or antiaggregants.
• Diabetes mellitus.
• Cardiac dysfunctions.
• Infiltrative and/or rehabilitative treatment in the two months prior to recruitment.
• Pre-existing diseases associated with pain in the upper extremities.
• Difficulties of follow-up.
• Depression.
• Treatment with another intervention, during the development of the study will not be able to perform.

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