The upper extremities are necessary to independently perform everyday activities, engage with the environment and others and, importantly, work. Unfortunately, upper extremity (UE) conditions, resulting in pain and impairments, are common. Although returning to work is usually straightforward, for some it can be difficult and prolonged, impacting significantly on the worker, key stakeholders and society.This thesis utilized mixed methodology to explore factors influencing RTW following surgery for traumatic and non-traumatic UE conditions. Specifically, the overall aims were to: 1) identify gaps in the literature; 2) generate a list of factors influencing RTW; 3) explore stakeholders perspectives of barriers and the strategies to facilitate RTW; 4) determine the assessment tools used by health care providers (HCPs) to evaluate RTW barriers; 5) clarify a definition for delayed RTW; and 6) explore injured workers' lived experiences to understand the context surrounding the factors and processes that may influence RTW.A scoping review identified gaps in the literature (Aim 1), generating the remaining thesis aims. A systematic review of prognostic studies for RTW following a common UE surgery, carpal tunnel release, was then conducted (Aim 2). This review revealed an inconsistent and low level of evidence for any studied prognostic factor for RTW or work disability.A three-round Delphi study determined expert opinion on the barriers and facilitators for RTW following surgery for non-traumatic UE conditions (Aim 2). Thirty-one experts completed all rounds. Strong consensus was achieved for these barriers: mood disorder; symptoms at more than one site; heavy UE work exertions; lack of flexible RTW arrangements; lack of supervisor support; and high pain catastrophising. Strong consensus was achieved for these facilitators: high motivation to RTW; high RTW and recovery selfefficacy; availability of modified duties; flexible RTW arrangements; positive coping skills; limited heavy UE work exertions; no catastrophic thinking; no fear avoidance to RTW, pain or activity; return to meaningful work duties; supportive RTW policies; supportive supervisor; and high job satisfaction.A cross-sectional study of 1011 RTW stakeholders (HCPs, employers, insurers and lawyers) was conducted. This study contained four sub-studies. In the first sub-study, a list ii of factors that stakeholders perceived influence RTW was generated (Aim 2). Highest agreement was found for: RTW self-efficacy; post-operative psychological status; supportive employer or supervisor; employer's willingness to accommodate job modifications; worker's recovery expectations; mood disorder diagnosis; post-operative pain level; and whether the job can be modified. Disagreements between stakeholder groups existed for a third of the factors. Further analysis of the 787 HCPs was conducted in sub-study two (Aim 2). This revealed that HCPs rated difficulty coping with the pain as the main RTW barrier. Few differences between the disciplines existed.In sub-study th...