Background: Long-term musculoskeletal complications represent a growing burden for survivors of childhood acute lymphoblastic leukemia (cALL). This study aimed to describe impairments, activity limitations, and participation restrictions of survivors of cALL at highest risk for late morbidity (PETALE cohort). Procedure: This retrospective study, using cross-sectional observational data from the PETALE cohort, included a subgroup of survivors who presented extreme phenotypes of late effects. Participants completed bilateral hip magnetic resonance imaging (MRI), assessment of maximal isometric muscle strength (MIMS), range of motion (ROM), Near Tandem Balance (NTB), 6-Minute Walk Test (6MWT), Five Time Sit-to-Stand Test (FTSST)), and quality of life (QOL). Descriptive statistics and regression analyses were performed. Results: 97 survivors were included in this study. The selected survivors (24.2 ± 6.7 years old) trended toward lower scores for most outcomes compared to available expected values referenced from a healthy population except for QOL. Thirteen participants (14.6%, 18 hips) had hip ON (53.8% male). Female survivors had hip ON with higher severity score (66.7% female vs. 22.2% male). Survivors with hip ON had reduced hip external rotation ROM compared to those without (p<0.05). Relationships were found between MIMS and ROM outcomes, and with 6MWT. Our multiple linear regression model explained 27.6% of the variance of the 6MWT. Conclusions: Although they reported QOL in the range of healthy peers, long-term cALL survivors at highest risk for late morbidity had clinically significant impairments and activity limitations. These data are in keeping with the frailty phenotype described in childhood cancer survivors.