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

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