A commentary by H. Kerr Graham, MD, Pam Thomason, BPhty, MPhysio, and Morgan Sangeux, PhD, is linked to the online version of this article at jbjs.org. Long-Term Outcomes of Distal Femoral Extension Osteotomy and Patellar Tendon Advancement in Individuals with Cerebral Palsy Elizabeth R. Boyer, PhD, Jean L. Stout, MS, PT, Jennifer C. Laine, MD, Sarah M. Gutknecht, NP, Lucas H. Araujo de Oliveira, MD, Meghan E. Munger, MPH, Michael H. Schwartz, PhD, and Tom F. Novacheck, MD Investigation performed at Gillette Children’ s Specialty Healthcare, St. Paul, Minnesota Background: We examined long-term outcomes across the domains of the International Classification of Functioning, Disability and Health for 2 groups of participants with cerebral palsy who demonstrated crouch gait at clinical gait analysis. One group underwent a distal femoral extension osteotomy with patellar tendon advancement (DFEO 1 PTA). The other group received other treatments (non-DFEO 1 PTA). Methods: Fifty-one participants returned for a long-term gait analysis, physical examination, energy consumption test, knee radiographs, and questionnaires (median, 13 years post-DFEO 1 PTA or post-baseline [range, 8 to 21 years]). A subset of participants in the DFEO 1 PTA group also had a short-term analysis (9 to 24 months postoperatively). Results: Participants were reasonably well-matched at baseline, although the DFEO 1 PTA group demonstrated greater crouch: minimum knee flexion, a median of 37° (width of the interquartile range, 12°) compared with 27° (9°); and knee flexion contracture, a median of 15° (10°) compared with 10° (5°). The gait deviation index (GDI) and sagittal plane knee kinematics were most improved at short term for the DFEO 1 PTA participants, with a subsequent slight decline at long- term analysis. Fewer DFEO 1 PTA participants were in crouch at long term (37% compared with 65%). At the long-term assessment, group scores for function, mobility, participation, quality of life, and most pain questionnaires were similar. Knee pain and osteoarthritis ratings did not differ between the groups. Conclusions: At long-term analysis, DFEO 1 PTA improves stance phase knee extension and knee flexion contracture compared with conventional treatment, but these benefits do not translate to improved activity, participation, or knee pain in early adulthood. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence. M any adolescents with cerebral palsy (CP) demonstrate a crouch gait in walking 1-3 , which is typically character- ized by excessive knee flexion throughout stance 3 . Without treatment, gait may improve or deteriorate 4 . On the basis of musculoskeletal modeling, crouch gait places the psoas, and possibly the hamstrings, in a functionally shortened state 5,6 , which may contribute to contracture development or worsening 4 . In addition, both knee flexion contracture and knee flexion in gait are associated with patellar fracture 7,8 , chondromalacia 9 , and pa- tella alta 8 . Treatment is often sought because of the association with knee pain, the progressive nature, possible social stigma, and increased energy consumption 10 . A distal femoral extension osteotomy (DFEO) removes an anterior femoral wedge (trapezoid if shortening the limb) to straighten the knee 11 . A patellar tendon advancement (PTA) or, if the patient is skeletally mature, a tibial tubercle advancement, is Disclosure: This work and E.R. Boyer’s position are supported by the Gait and Motion Outcomes Fund of the Gillette Children’s Foundation. The study sponsors had no role in the study design, collection, analysis, and interpretation of data, writing of the manuscript, or the decision to submit the manuscript for publication. No external funding was received for this study. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article ( http://links.lww.com/JBJS/E494). 31 COPYRIGHT Ó 2018 BY THE J OURNAL OF BONE AND J OINT SURGERY,I NCORPORATED J Bone Joint Surg Am. 2018;100:31-41 d http://dx.doi.org/10.2106/JBJS.17.00480