Patient-reported outcome measures have become important tools for assessing health status in a variety of patient populations. Many historically or commonly used patient-reported outcome measures in orthopaedics are narrow in scope and are limited by the burden associated with their administration, making them useful only for specific populations. The Patient-Reported Outcomes Measurement Information System (PROMIS) was developed to overcome these limitations. The system was developed using item response theory, which allows for reliable and efficient estimation of underlying health traits using targeted item banks to assess physical function in the upper and lower extremities. PROMIS has been validated in patient populations with orthopaedic disorders of the foot and ankle, upper extremity, and spine and has demonstrated a marked improvement in measurement characteristics and reduced patient and administrative burden. PROMIS Physical Function measures are useful for assessing orthopaedic outcomes and are superior to legacy measures in several key populations.