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

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