Chapter 7 86 The aim of the present study was therefore to investigate the effectiveness of PWB in surgically treated trauma patients with peri- and intra-articular fractures of the lower extremities, reporting on patients’ self-perceived outcome levels regarding ADL, quality of life, pain, weight bearing or patients’ compliance and postoperative complications, in comparison to RWB, over a 26-week post-surgery follow-up period. Methods Study design and participants This prospective comparative multicenter cohort study included surgically treated trauma patients with peri- and intra-articular fractures of the lower extremities. Subjects were consecutively recruited from six hospitals in the Netherlands between October 2017 and September 2018. The allocation of the patients to the intervention or control group depended on the regimen adhered to by the hospital in which the patients were surgically treated. During the conceptualization of this study design, an important choice had to be made concerning randomization. Patient randomization was not considered feasible because of the nature of the two different interventions. Implementation of these different protocols includes patient instructions as well as physical therapy guidance and nursing staff participation. A mix of treatment protocols on a single ward was therefore considered suboptimal because of information bias. However, this meant we had to take into account that not randomizing the study could introduce observer bias, which may be a study limitation. Patients from two hospitals underwent the PWB protocol2 as aftercare rehabilitation treatment, while the others followed the RWB1 protocol. Surgically treated trauma patients with peri- and intra-articular fractures of the lower extremities (i.e. pelvic fractures, acetabular fractures, distal femur fractures, tibial plateau fractures, pilon fractures, calcaneal fractures and talar fractures) were eligible for inclusion if they were aged 18 years or over. Patients with pathological fractures, shaft fractures treated with intra-medullary nailing, hip fractures treated with prosthesis, or fractures treated with external fixation, and patients with amputations in the area of the lower extremity, were excluded. Patients with cognitive dysfunction to follow instructions or due to the consequences of severe neurotrauma or due to concomitant or mental illness were also excluded.16 Protocols The PWB treatment involves a gradual progression in functional activities guided by patients’ subjective experience (pain and confidence to bear weight) and by objective clinical symptoms of the patients occurring during the process of rehabilitation,