IntroductionWe aimed to describe Quality of life (QoL) among adolescents with Patellofemoral Pain (PFP) and Osgood-Schlatter Disease (OSD) according to the QoL subscale of The Knee injury and Osteoarthritis Outcome Score (KOOS) and the EuroQol 5-dimensions (EQ-5D) and to investigate the characteristics associated with QoL.MethodsThis individual participant analysis included data from three clinical trials on adolescents diagnosed with PFP or OSD. We relabeled individual data and constructed a single dataset.ResultsWe included 323 adolescents with PFP or OSD. Total score of KOOS-QoL was 51±18 and total index score for the EQ5D was 0.67±0.21. KOOS-QoL subscale showed that 59% reported being aware of their knee problems daily or constantly, 37% reported severe to extreme lack of confidence in their knees, 27% reported severe to extreme difficulty with their knees, and 20% reported severely or totally modifying their lifestyle to avoid potentially damaging activities to their knee. EQ-5D showed that 77% experienced problems with everyday activities, 47% reported mobility problems, 17% felt worried, sad, or unhappy, and 7% reported problems looking after themselves. Older participants (age 17-19) reported worse QoL than younger participants. None of the other characteristics were associated with QoL.ConclusionsA high proportion of adolescents with chronic non-traumatic knee pain experience low QoL. More than half were aware of their knee problems at least daily, one in three reported a severe lack of confidence in their knee, and one in six felt worried, sad, or unhappy. QoL was lowest among older adolescents.Highlights-One in every three adolescents with PFP or OSD reported a severe lack of confidence in their knee.-Many adolescents reported being sad or worried, and modified their usual activities due to their knee pain.-Clinicians may extend the scope and include pain management strategies to address psychological perspectives when managing adolescents diagnosed with PFP or OSD.-Modifiable targets such as adolescents understanding of pain may be a beneficial management strategy to consider in rehabilitation for PFP or OSD.