The development, validation and internal consistency of the Norwich Patellar Instability (NPI) score

Smith, Toby, Donell, Simon, Clark, Allan, Chester, Rachel, Cross, Jane, Kader, Deiary and Arendt, Elizabeth (2014) The development, validation and internal consistency of the Norwich Patellar Instability (NPI) score. Knee Surgery, Sports Traumatology, Arthroscopy, 22 (2). pp. 324-335. ISSN 0942-2056

Full text not available from this repository. (Request a copy)
Official URL:


Purpose - No outcome measurements have previously been designed to assess patient-perceived patellar instability. The purposes of this study were to address this limitation and to describe the development and validation of the Norwich Patellar Instability (NPI) scores, a self-administered 19-item questionnaire to assess perceived patellar instability.

Methods - A previous study assessed activities that aggravated symptoms in individuals with patellar dislocation and instability symptoms. These reported activities were ranked in order of severity, and a weighting system was calculated. The NPI score was introduced to routine clinical practice in three institutions. One hundred and two people who had experienced a lateral patellar dislocation completed 102 NPI questionnaires. The completed NPI score was correlated with the Knee injury and Osteoarthritis Outcome Score (KOOS) to evaluate divergent validity and with the J-sign, patellar mobility, apprehension test, Beighton score, Kujala Patellofemoral Disorder Score and Lysholm Knee Score to evaluate convergent validity. Internal consistency of the 19 items was also calculated.

Results - The results indicated a moderate correlation between the NPI score and the Kujala Patellofemoral Disorder Score (rho = −0.66; p < 0.01) and Lysholm Knee Score (rho = −0.54; p = 0.03), suggesting good convergent validity. There was a little correlation between the KOOS and NPI score, indicating divergent validity (rho = −0.02 to −0.17; n.s.). There was high internal consistency (Cronbach’s alpha = 0.93).

Conclusion - These results indicate the NPI score to be a valid tool to assess patellar instability for individuals following patellar dislocation. Further study is now required in order to assess the reliability and responsiveness of this new outcome measure.

Item Type: Article
Uncontrolled Keywords: Patella, dislocation, instability, outcome measure, construction, validation
Subjects: B900 Others in Subjects allied to Medicine
Department: Faculties > Health and Life Sciences > Sport, Exercise and Rehabilitation
Depositing User: Becky Skoyles
Date Deposited: 13 Mar 2014 08:56
Last Modified: 12 Oct 2019 16:26

Actions (login required)

View Item View Item


Downloads per month over past year

View more statistics