The aim of the study is to determine "the additional effect of... function" for patellofemoral pain syndrome (PFPS). The additional effect of orthotic devices over exercise therapy on pain and function. A systematic literature search was conducted in MEDLINE, CINAHL, EMBASE, Cochrane and PEDro. Randomised controlled trials and controlled clinical trials of patients diagnosed with PFPS evaluating a clinically relevant outcome were included. Treatment had to include exercise therapy combined with orthotics, compared with an identical exercise programme with or without sham orthotics. Data were summarised using a best evidence synthesis. Eight trials fulfilled the inclusion criteria, of which three had a low risk of bias. There is moderate evidence for no additive effectiveness of knee braces to exercise therapy on pain (effect sizes (ES) varied from -0.14 to 0.04) and conflicting evidence on function (ES -0.33). There is moderate evidence for no difference between knee braces and exercise therapy versus placebo knee braces and exercise therapy on pain and function (ES -0.1-0.10). More studies of high methodological quality are needed to draw definitive conclusions.