The Norwich Patellar Instability Score: Validity, internal consistency and responsiveness for people conservatively-managed following first-time patellar dislocation

T O Smith; R Chester; N Hunt; J L Cross; A Clark; S T Donell

doi:10.1016/j.knee.2015.10.003

The Norwich Patellar Instability Score: Validity, internal consistency and responsiveness for people conservatively-managed following first-time patellar dislocation

Knee. 2016 Mar;23(2):256-60. doi: 10.1016/j.knee.2015.10.003. Epub 2016 Jan 18.

Authors

T O Smith¹, R Chester², N Hunt³, J L Cross², A Clark⁴, S T Donell⁵

Affiliations

¹ School of Health Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, United Kingdom. Electronic address: toby.smith@uea.ac.uk.
² School of Health Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, United Kingdom.
³ Physiotherapy Department, Norfolk and Norwich University Hospital, Colney Lane, Norwich NR4 7UY, United Kingdom.
⁴ Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, United Kingdom.
⁵ Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, United Kingdom; Norfolk and Norwich University Hospital, Colney Lane, Norwich NR4 7UY, United Kingdom.

PMID: 26794922
DOI: 10.1016/j.knee.2015.10.003

Abstract

Background: This paper assessed the validity, internal consistency, responsiveness and floor-ceiling effects of the Norwich Patellar Instability (NPI) Score for a cohort of conservatively managed people following first-time patellar dislocation (FTPD).

Methods: Fifty patients were recruited, providing 130 completed datasets over 12 months. The NPI Score, Lysholm Knee Score, Tegner Level of Activity Score and isometric knee extension strength were assessed at baseline, six weeks, six and 12 months post-injury.

Results: There was high convergent validity with a statistically significant correlation between the NPI Score and the Lysholm Knee Score (p<0.001), Tegner Level of Activity Score (p<0.001) and isometric knee extension strength (p<0.002). Principal component analysis revealed that the NPI Score demonstrated good concurrent validity with four components account for 70.4% of the variability. Whilst the NPI Score demonstrated a flooring-effect for 13 of the 19 items, no ceiling effect was reported. There was high internal consistency with a Cronbach Alpha value of 0.93 (95% CI: 0.91 to 0.93). The NPI Score was responsive to change over the 12 months period with an effect size of 1.04 from baseline to 12 months post-injury.

Conclusions: The NPI Score is a valid tool to assess patellar instability symptoms in people conservatively managed following FTPD.

Level of evidence: Level II.

Keywords: Instability; Instrument; Outcome measure; Patellar dislocation; Physiotherapy; Reliability; Validity.

Publication types

Randomized Controlled Trial
Research Support, Non-U.S. Gov't

MeSH terms

Female
Follow-Up Studies
Humans
Joint Instability / diagnosis*
Joint Instability / etiology
Joint Instability / rehabilitation
Lysholm Knee Score*
Male
Patellar Dislocation / complications
Patellar Dislocation / diagnosis
Patellar Dislocation / rehabilitation*
Physical Therapy Modalities*
Reproducibility of Results
Retrospective Studies
Time Factors
Young Adult