Patellofemoral pain syndrome is one of the most common orthopaedic complaints presenting to physical therapists. Although its etiology is uncertain, the cause is most often considered to be malalignment or lateral tracking of the patella. Consequently, measurement of patellar alignment has come to be accepted as an integral part of the examination of patellofemoral pain syndrome. Various measurement techniques exist, both clinical and radiological, and these have been frequently used in the diagnosis and treatment of the condition. As a corollary, the widespread use of such measurements has also lent weight to the theory that patellar malalignment is one of the primary causes of patellofemorai pain syndrome. However, an analysis of the literature reveals that the vast majority of these measurement procedures lack the appropriate scientific qualities to be considered acceptable measurement tools, including questionable reliability and validity, and an absence of appropriate normative data and a gold standard. This paper assesses the evidence for the usefulness of the most commonly used measures of patellar alignment and concludes that many of the beliefs of the clinical community with regard to the existence and measurement of patellar malalignment in patellofemoral pain syndrome may be based largely on assumptions and not on evidence.