The experimental group will receive intralesional injections of platelet-rich plasma, evaluating its ability to relieve pain and provide sustained improvement through biological modulation of the joint and tendon environment. In contrast, the control group will be treated with a combination of betamethasone and ropivacaine, representing the current standard of care for short-term inflammatory pain management. The comparison between these two options will determine whether platelet-rich plasma offers advantages in terms of clinical efficacy and duration of benefits. The results obtained could contribute significantly to the development of more effective protocols and more precise management guidelines for patients with chronic omalgia, thus addressing existing controversies and improving clinical practice.

Inclusion Criteria:

• Patients between 35 and 75 years of age, both inclusive.
• Presence of pain in the affected shoulder for 3 or more months.
• Body Mass Index (BMI) values between 20 and 27 kg/m2, including both values.
• Confirmed diagnosis of chronic shoulder pain associated with rotator cuff tendinopathy, following an unfavorable response to standard treatment with analgesics and nonsteroidal anti-inflammatory drugs for 4-6 weeks.
• Patients who agree to participate in the study and sign the informed consent form.

Exclusion Criteria:

• Confirmed diagnosis of complete rotator cuff tear.
• Patients with systemic autoimmune rheumatic disease (connective tissue diseases and systemic necrotizing vasculitis).
• Patients with diabetes mellitus.
• Patients with hematological disorders (thrombopathy, thrombocytopenia, anemia with Hb<9 g/dl).
• Patients undergoing immunosuppressive treatment at the time of inclusion.
• Patients undergoing treatment with intramuscular corticosteroids in the 3 months prior to the first administration of the trial treatment.
• Patients undergoing treatment with nonsteroidal anti-inflammatory drugs (more than 10 consecutive days at usual doses), opioids, or oral corticosteroids during the 15 days prior to treatment in the study.
• Patients with severe heart disease.
• Patients with active cancer or cancer diagnosed in the last 5 years.
• Patients who are taking a drug in clinical trials or have participated in any clinical trial (with an authorized or unauthorized product) in the 30 days prior to randomization.
• Patients with any physical, social, or psychological condition that, in the opinion of the investigators, may affect the patient's participation in the trial or the validity of the data obtained from their participation in it.
• Pregnant women.
• Breastfeeding women.
• Women of childbearing age* who are unable or unwilling to use contraceptive methods with a failure rate of <1% per year (bilateral tubal ligation, hormonal contraceptives that inhibit ovulation, hormone-releasing intrauterine devices, and copper intrauterine devices) during the four-week treatment period.