Patient-reported outcomes (PROs) are widely used in the orthopaedic field to assess the impact of conservative and surgical interventions from a patient's perspective. Available instruments cover a range of outcome parameters, such as pain, function, stiffness, quality of life or joint awareness. Choice of instrument for a specific study for clinical practice should include the appraisal of the psychometric characteristics of the measure. The presentation will focus on the assessment of the psychometric characteristics of PRO instruments and provide criteria for evaluating those. The concepts of objectivity, reliability and validity will be explained in the context of PRO instrument and the interpretation of score points derived from PRO instruments will be discussed detailing concepts such as minimal important change/difference, norm data, and thresholds based on external criteria. Finally, international guidelines that define standards for the various procedures on development, validation and translation of PRO instruments will be summarised.