The American Orthopaedic Foot & Ankle Society (AOFAS) has developed four rating systems, in which the clinical status of the ankle and foot is reported [16]. In the original publication, the AOFAS ankle-hindfoot score was described to be used for ankle replacement, ankle arthrodesis, ankle instability operations, subtalar arthrodesis, subtalar instability operations, talonavicular arthrodesis, calcaneocuboid arthrodesis, calcaneal osteotomy, calcaneus fracture, talus fracture, and ankle fractures [16]. This scale incorporates both subjective and objective factors with a maximal score of 100, indicating no symptoms or impairments. The scale includes nine items that can be divided into three subscales (pain, function, and alignment). Pain consists of one item with a maximal score of 40, indicating no pain. Function consists of seven items with a maximal score of 50, indicating full function. Alignment consists of one item with a maximal score of 10, indicating good alignment.

The AOFAS ankle-hindfoot score, as a complete score, has been shown to be valid [22, 37, 51]. The score has shown good responsiveness over time in two studies, with reported effect sizes of 1.69 [22] and 1.12 [38]. The subjective portion of the scale has been shown to be valid and reliable [12]. The objective portion of the scale has not been evaluated for reliability. This is one of the main criticisms of the AOFAS score. The second major concern of the AOFAS score is the weighting and calculations of the items; for example, high scores are obtained relatively easily (i.e., ceiling effect). Furthermore, the subscale pain is heavily weighted (40 points), and there is a 20-point difference between rating pain as severe (almost always present) and moderate (daily). To establish reliability, validity, and responsiveness, the scale has been evaluated related to a wide spectrum of diagnoses, such as general ankle-hindfoot complaints [37], pending ankle or foot surgery [12], surgically treated calcaneal fractures [51], and end-stage ankle arthritis [22]. However, there is no study that has evaluated the psychometric properties in patients with talar OCD.

The Foot and Ankle Outcome Score (FAOS) [32] is a patient-reported score, which evaluates symptoms and functional limitations related to the foot and ankle (www.​koos.​nu). It includes five different subscales: pain (nine items), other symptoms (stiffness, swelling, and range of motion; seven items), activities of daily living (17 items), sports and recreational activities (five items), and foot-and-ankle-related quality of life (four items). The items are scored on a 0–4-point scale and then normalized, resulting in a subscale score of 0–100. A score of 100 equals no symptoms or difficulty with activities. The FAOS is based on the Knee injury and Osteoarthritis Outcome Score (KOOS) and has been shown to have good validity and reliability in patients with ankle injury [32]. When used as an outcome measure for patients with Achilles tendinopathy, it has been shown to be responsive to changes over time [17, 33]. No study has evaluated the minimal clinically important difference, nor has the reliability or validity been investigated specifically for talar OCD. The FAOS is available in numerous languages (www.​koos.​nu), enabling its use in international multicenter studies.