Chronic pain is a global public health problem, which intensifies even more in the obese population, reaching about 33% of these patients. Among the topography, chronic knee pain affects 80%, constituting an important cause of disability and decreased quality of life. In addition, in grade 3 obesity, also called morbid obesity, in which bariatric surgery is already indicated, knee pain makes it difficult or prevents participation in the pre-habilitation program that includes physical therapy through therapeutic exercises with the aim of reducing postoperative complications. In this sense, a double-blind, randomized, placebo-controlled clinical trial will be conducted with the objective of evaluating the effect of photobiomodulation (PBM) on pain and functionality of obese patients with chronic knee pain who are in a prehabilitation program for bariatric surgery, discussing its role as an analgesic therapy and modifier of peripheral and central sensitization mechanisms of the pain pathway. PBM is a safe treatment option, with no undesirable effects and low cost. The primary outcomes will be pain intensity, through visual analogue scale, and Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire, validated version for Portuguese - Brazil. Secondary outcomes will be pressure pain threshold and rolling pinch maneuver measured by digital algometer. Other exploratory outcomes will be 6-minute walk test, knee range of motion, SF-36 quality of life questionnaire. There will be 2 groups: an intervention group (photobiomodulation associated with standard physiotherapy treatment) and another placebo group (device turned off associated with the same standard physiotherapy treatment). The application sites will be knees and lumbar paravertebral 2 times a week for 12 weeks. The dosimetric standards will be 4J/point in the knees and 3J/point in the lumbar. The results obtained will be statistically analyzed and later published in a scientific journal.

Chronic pain is a global public health problem, which intensifies even more in the obese population, reaching about 33% of these patients. Among the topography, chronic knee pain affects 80%, constituting an important cause of disability and decreased quality of life. In addition, in grade 3 obesity, also called morbid obesity, in which bariatric surgery is already indicated, knee pain makes it difficult or prevents participation in the pre-habilitation program that includes physical therapy through therapeutic exercises with the aim of reducing postoperative complications. In this sense, a double-blind, randomized, placebo-controlled clinical trial will be conducted with the objective of evaluating the effect of photobiomodulation (PBM) on pain and functionality of obese patients with chronic knee pain who are in a prehabilitation program for bariatric surgery, discussing its role as an analgesic therapy and modifier of peripheral and central sensitization mechanisms of the pain pathway. PBM is a safe treatment option, with no undesirable effects and low cost. The primary outcomes will be pain intensity, through visual analogue scale, and Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire, validated version for Portuguese - Brazil. Secondary outcomes will be pressure pain threshold and rolling pinch maneuver measured by digital algometer. Other exploratory outcomes will be 6-minute walk test, knee range of motion, SF-36 quality of life questionnaire. There will be 2 groups: an intervention group (photobiomodulation using Therapy EC-DMC device associated with standard physiotherapy treatment) and another placebo group (device turned off associated with the same standard physiotherapy treatment). The application sites will be knees (4 anatomically described points) and lumbar paravertebral (levels L3 to S2 bilateral - 10 points, being 05 points each side) 2 times a week for 12 weeks. The dosimetric standards will be 4J/point (40 seconds) in the knees and 3J/point (30 seconds) in the lumbar. The results obtained will be statistically analyzed using SPSS 28.0 software, and later published in a scientific journal.

Inclusion Criteria:

• Obese patients with indication for bariatric surgery performed in routine follow-up at the Gastric Surgery Outpatient Clinic of HC-UFG;
• Patients with chronic pain (> 3 months) in the knees bilaterally. Patients will be asked in the initial evaluation if they feel pain located in the topography of the knees that has been compromising their functionality both in daily activities and at work, and that lasts for more than or equal to 3 months. This pain may be reported as continuous or intermittent;
• Sign the Informed Consent Term approved by the HC-UFG Ethics Committee.

Exclusion Criteria:

• - Loss of follow-up in the outpatient clinic of origin and in the Physiotherapy sector, even though the use of laser therapy was maintained according to the study protocol;
• Any reported adverse effects from the use of FBM reported;
• Patients in whom there are changes in the medications being used for chronic pain during the study protocol will be excluded from this study. Minimal changes in the dosages of medications already in use can be tolerated, as long as there are no changes in the type of medication, but only in the prescribed dose. These modifications throughout the study, if they occur, will be described.
• Death
• Withdrawal of the informed consent by the participant
• If the patient, for any reason, is excluded from the indication of bariatric surgery
• Emergence during the study of any of the non-inclusion criteria, like: .
• Patients with other rheumatologic diseases and/or systemic inflammatory diseases (rheumatoid arthritis, Reiter's arthritis, ankylosing spondylitis, generalized polyarthritis) or previous musculoskeletal diseases in the knees;
• Clinical manifestations or complaints of knee arthralgia related to diseases other than obesity.
• Previous use in the last 90 days of treatment with the use of Phototherapy for the same or another indication;
• Clinical signs of neuropathy, including radiculopathies and peripheral nerve injuries;
• Pain in the lower limb, originating from the lumbar spine (lombosciatalgia)
• Use of corticosteroids at an immunosuppressive dose (20mg daily of prednisone or equivalent for at least 14 days);
• Infection or tumor at the site of therapy application;
• Current chronic infections such as tuberculosis or chronic hepatitis treated or not.
• Blood clotting disorders (including thrombosis) at the application site.
• Diagnosis of fibromyalgia;
• Serious psychiatric disorders that require psychiatric care;
• Systemic injections and/or joint injections of corticosteroids or hyaluronic acid during the last 48 hours prior to the initial assessment of the study;
• Psychoaffective disorder that compromises adherence to treatment;
• Any history of sensitivity to light or phototherapies.

The plan of Data Manage are available in

https://doi.org/10.48321/D1MW8J Rebeca Cecatto. (2023). "Photobiomodulation in Chronic Knee Pain in Patients Who Are in PreRehabilitation for Bariatric Surgery: Double Blind, Randomized, Controlled Placebo Clinical Trial " [Data Management Plan]. DMPTool. https://doi.org/10.48321/D1MW8J

The registered study protocol will be submitted to publication in a scientific journal making the protocol public before the collected data. Upon completion of the study, the original clinical non-identifiable data referring to pain, quality of life and functionality assessments will be made available in repository, with the purpose of collaborating with the scientific community and auditing. These data collected and stored in the spreadsheets drives will be exported to an Open Science repository such as Mendeley Data, Figshare or similar. The results after the statistical analysis will also be sent for publication in indexed scientific journals.

follow the policies of these platforms and scientific journals

Participant: The participant will be blind to the group they will be participating in. The device display will be hidden so the patient cannot see if it is on or off. The device activation noise will be recorded and used to mimic the irradiation.

Principal Investigator: only the auxiliary investigator who will apply the laser will know the group of participants. The principal investigator performing the initial and final (post-treatment) assessments will be blinded to the treatment/placebo groups