Contents lists available at ScienceDirect Research in Developmental Disabilities journal homepage: www.elsevier.com/locate/redevdis Review article The natural history of crouch gait in bilateral cerebral palsy: A systematic review Rory O’Sullivan a,b, ⁎ , Frances Horgan b , Tim O’Brien a , Helen French b a Gait Laboratory, Central Remedial Clinic, Dublin, Ireland b School of Physiotherapy, Royal College of Surgeons in Ireland, 123 St Stephens Green, Dublin 2, Ireland ARTICLE INFO Keywords: Cerebral palsy Crouch gait Knee flexion Kinematics ABSTRACT Aim: To systematically review the natural history of crouch gait in bilateral cerebral palsy (CP) in the absence of surgical intervention and to review any relationship between clinical variables and progression of knee crouch. Methods: Relevant literature was identified by searching article databases (PubMed, CINAHL, EMBASE, and Web of Science). Included studies reported on participants with bilateral CP who had 3-dimensional gait analysis on at least two occasions with no surgical interventions between analyses. Results: Five papers (4 retrospective cohort studies; 1 case report) comprised the final selection. Studies varied in follow-up times and participant numbers. Increased knee flexion over time was reported in the four retrospective studies with two distinct patterns of increasing knee flexion evident. Only the case-study reported improved knee extension between assessments. Four stu- dies demonstrated increased hamstring tightness over time with the biggest increases related to longer follow-up time rather than increase in crouch. Conclusion and Implications: The existing literature suggests that the natural history of crouch gait is towards increasing knee flexion over time. Future prospective studies of bigger groups are needed to examine the relationship between increasing crouch and clinical variables. What this paper adds? Crouch gait is very prevalent in cerebral palsy (CP) and has been shown to increase the forces acting on the knee and the energy cost of gait. It has been suggested that if left untreated this gait pattern can lead to pain, joint deformity, radiological abnormalities and loss of independent gait. This systematic review suggests that, in the absence of surgical intervention, the natural history of crouch gait is towards increasing knee flexion over time. The rate of progression of crouch gait appears to increase in those with knee flexion greater than 20° during gait suggesting that this might be an indicator for more urgent intervention. While studies have shown that not all those who walk in crouch have short hamstrings, this pattern is typically treated with surgical lengthening of this muscle group. This systematic review found that while hamstring tightness increased over time, this appeared to occur secondary to walking in crouch rather than contributing to the progression of this pattern. However, the results should be interpreted with caution due to the limited number of studies meeting the inclusion criteria of this systematic review as well as the methodological limitations of the included studies. This review highlights that longer term follow ups of larger numbers are needed to examine the multi-factorial nature of crouch progression in CP. Any further study should include assessment of function and participation in conjunction with gait analysis in the laboratory. https://doi.org/10.1016/j.ridd.2018.06.013 Received 18 October 2017; Received in revised form 5 April 2018; Accepted 19 June 2018 ⁎ Corresponding author at: Central Remedial Clinic, Vernon Avenue, Clontarf, Dublin 3, Ireland. E-mail addresses: rosullivan@crc.ie, roryosullivan@rcsi.com (R. O’Sullivan). Research in Developmental Disabilities 80 (2018) 84–92 0891-4222/ © 2018 Elsevier Ltd. All rights reserved. T