In 2007 Prof. Markus S. Kuster, an experienced arthroplasty surgeon, had the idea of developing a questionnaire for the reliable and valid assessment of the forgotten joint concept. The FJS-12 Knee was published in 2012 by Henrik Behrend, Karlmeinrad Giesinger, Johannes M. Giesinger and Markus S. Kuster in the Journal of Arthroplasty.
The FJS Knee was designed to assess patient outcome in patients undergoing conservative or operative treatment of the knee. This questionnaire shows its strengths in patients with a good level of knee function and a low pain level. It has been designed specifically to reduce ceiling effects commonly associated with many PRO measures in this patient group, e.g. when assessing short- to mid-term results in total knee arthroplasty patients.

The FJS-12 Knee has an increasing number of clinicians and researchers (in e.g. Switzerland, UK, Belgium, Japan) using this novel score.

We are planning to further improve the assessment of joint awareness in knee patients through development of a comprehensive item bank. This will allow computer-adaptive assessments (CAT). A CAT prototype for the FJS Knee has been published in 2013. This pilot study was designed to test unidimensionality (internal consistency) of the Forgotten Joint concept and to investigate the association of item number and measurement precision for this construct. A very important  finding was the fact that the assessment of joint awareness in hip and knee patients cannot rely on the same measurement model due to extensive differential item functioning.

Naturally, CAT scores from this item bank will be comparable with the FJS-12 Knee.

Development of this item bank will rely on an extensive literature search, expert opinion and patient interviews to create an initial item list that will be used in a large international field study to develop a measurement model and psychometric item characteristics.

We encourage researchers and clinicians with an interest to participate in this field study to contact us. Additional languages to German and English are most welcome to foster international collaborations and studies.