Low-Level Laser Therapy for Osgood-Schlatter or Sever Pain in Youth Athletes

Effect of Low-Level Laser Photobiomodulation on Pain, Function, and Ultrasound Findings in Youth Athletes With Osgood-Schlatter Disease or Sever Disease: A Randomized, Double-Blind, Sham-Controlled Pilot Trial

The goal of this clinical trial is to learn if low-level laser therapy (also called photobiomodulation) works to treat knee or heel pain in physically active children and adolescents with Osgood-Schlatter disease or Sever disease. It will also learn about the safety of this treatment. The main questions it aims to answer are:

1. Does low-level laser therapy lower pain more than a sham (placebo) laser treatment?
2. Does low-level laser therapy improve daily and sport-related function more than a sham laser treatment?
3. What medical problems, if any, do participants have during the study?

Researchers will compare active low-level laser therapy to a sham (placebo) laser treatment. The sham treatment looks and feels the same but does not deliver therapeutic light. This comparison will show whether the laser therapy works better than placebo.

Participants will:

• Complete screening and a baseline visit
• Be randomly assigned to active laser therapy or sham laser therapy
• Receive a series of treatment sessions over [2 weeks]
• Answer short questionnaires about pain and function at baseline and follow-up visits
• Have ultrasound imaging and/or provide blood or urine samples for research measurements

Both participants and the study team who assess outcomes will not know which treatment group each participant is in until the study ends.

This pilot randomized, placebo-controlled, double-masked clinical trial evaluates the feasibility and preliminary clinical signal of laser photobiomodulation (low-level laser therapy; LLLT) in youth athletes (10-17 years) with symptomatic lower-extremity apophyseal pathology, primarily consistent with Osgood-Schlatter disease and/or calcaneal apophysitis (Sever disease) confirmed clinically and by ultrasound.

Participants will be randomized 1:1 to active LLLT or sham LLLT. The intervention consists of 10 sessions over 2 weeks (5 sessions/week) delivered with a class 3B GaAlAs (Gallium-Aluminum-Arsenide) laser device using standardized parameters (near-infrared wavelength range; continuous mode; preset energy density; contact application over the symptomatic apophyseal region). Sham procedures are identical in appearance, session duration, and device operation but deliver 0 mW output.

The primary objective is feasibility (recruitment, retention, adherence, data completeness, safety). Secondary objectives are estimate-only between-group differences in pain and function at post-intervention and follow-up. Ultrasound is repeated after the intervention as an exploratory mechanistic assessment. Blood and urine biomarkers are collected at baseline only and are not analyzed as post-intervention randomized outcomes.

After completion of the blinded 2-week intervention and immediate post-intervention assessment, participants may enter the separately registered rehabilitation pathway (NCT07521280). Subsequent rehabilitation and other treatment exposure will be documented when interpreting the 3-month follow-up outcomes.

Inclusion Criteria:

• Aged 10 to 17 years
• Participates in organized sport with at least 12 months of training history
• Has knee pain at the tibial tubercle (Osgood-Schlatter-type pain) and/or heel pain at the back of the heel (Sever-type pain)
• Pain is worse with activity and reproduced by pressing on the painful area
• Pain intensity is 3 out of 10 or higher on the Numeric Pain Rating Scale (NPRS) during the clinical visit and in the last week (0 = no pain, 10 = worst pain imaginable)
• Symptoms have been present for at least 2 weeks
• For heel pain consistent with Sever disease, the heel squeeze test is positive
• Ultrasound shows findings consistent with an apophyseal injury at the painful site
• Has no signs of acute illness or infection on the assessment day and during the previous 14 days (for example, fever or "flu-like" symptoms)
• A parent/guardian provides written informed consent
• The participant provides assent (agreement) to take part

Exclusion Criteria:

• Current pain episode started after an acute injury (for example, fall, collision, ankle sprain, or similar trauma)
• Prior surgery on the lower limb
• Known diagnosis of patellofemoral pain syndrome (pain around/behind the kneecap)
• Known patellar instability (recurrent kneecap dislocations or giving way)
• Known complex regional pain syndrome
• History of lower-limb fracture
• Ultrasound shows clinically important abnormalities in the assessed area that are not consistent with the target condition (for example, calcifications or other significant findings)
• Known chronic or systemic disease that may affect the musculoskeletal system (for example, inflammatory joint disease or other clinically significant chronic conditions)
• Received any of the following in the last 3 months: steroid injection, hydrodilatation, or laser therapy
• Used non-steroidal anti-inflammatory drugs (NSAIDs) (for example, ibuprofen, naproxen) within the last 14 days, or currently uses them
• Clinically important abnormal blood test results (complete blood count) that may affect safety or data validity
• Parent/guardian or participant does not agree to participate, or withdraws consent/assent