The purpose of this study is to investigate the effect of activity modification, exercises and a gradual return to sport in adolescents (age 10-14) with Osgood Schlatter disease. The primary outcome is self-reported recovery on a 7-point Likert scale at 3 months. Secondary endpoints include 4 and 8 weeks and 6 and 12 months after inclusion into the project. The adolescents will be recruited from primary schools, general practitioners and through online advertising on Facebook.

Inclusion Criteria:

• 10-14 years of age
• Pain at tuberositas patellae during two or more of the following activities: Sitting with a bent knee, squatting, running, jumping or stair ambulation
• Pain during palpation of tuberositas patellae
• Knee pain for 6 weeks or more

Exclusion Criteria:

• Other knee conditions that may manifest as anterior knee pain (Patellofemoral pain, iliotibial band syndrome, sinding-larson-johanson disease).
• Previous surgery
• Pain from the hip or back that interferes with activities of daily living.
• Habitual patella luxations
• Clinical suspicion of meniscal lesion

Data will be made publicly available no later than six months after the final publication.