Afsaneh Zeinalzadeh - Department of Physiotherapy, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
Salman Nazary-Moghadam - Department of Physiotherapy, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
Sayyed Hadi Sayyed Hoseinian - Orthopedic Research Center, Shahid Kamyab Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
Mohammad H. Ebrahimzadeh - Orthopedic Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
Esmaeel Imani - Department of Physiotherapy, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
Samira Karimpour - Department of Physiotherapy, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran

Background: To evaluate the relative and absolute reliability of reaction time measuring methods during differentconditions in participants with and without patellofemoral pain syndrome (PFPS).Methods: 30 patients with PFPS and 30 healthy controls were recruited in the present study. The upper extremityreaction time, upper extremity error rate, involved and non-involved lower extremity braking reaction times, and involvedand non-involved knee extension reaction times were measured. Each condition was repeated three times, 2 sessionswith a 5-7 days interval. The intra-session reliability was evaluated in three-trial (A), second- and third-trial (B) modes.In addition, the inter-session reliability was evaluated in mode A, mode B, and best score (C) mode.Results: The result of inter-session reliability of mode A showed that all measurements except upper extremity reactiontime in PFPS group showed high to very high relative reliability (ICC: 0.74-0.94). In mode B, all measurements exceptnon-involved knee extension reaction time in PFPS group showed high to very high relative reliability (ICC: 0.71-0.93).In mode C, all measurements showed high to very high relative reliability (ICC: 0.70-0.94) except upper extremity errorrate and non-involved knee extension reaction time in PFPS group. The result of intra-session reliability showed thatall measurements had high to very high relative reliability (ICC: 0.78-0.94) in mode A. In mode B, all measurementsshowed high to very high relative reliability (0.78-0.94).Conclusion: The braking time seems more reliable than other reaction time tasks. In addition, the results showedthat mode A is more reliable than other modes. The newly designed package is a reliable tool to measure the kneeextension reaction time in patients with knee musculoskeletal disorders.Level of evidence: II

knee, patellofemoral pain syndrome, Reaction time, Reliability