Initial validity and reliability of the Banff Patella Instability Instrument.

Area of Science:

• Orthopedics
• Patient-Reported Outcome Measures
• Knee Instability Research

Background:

• Patellofemoral instability is a common orthopedic issue.
• Existing quality of life measures lack disease specificity for this condition.
• A validated, patient-centered tool is needed for patellofemoral instability assessment.

Purpose of the Study:

• To establish content validity, construct validity, and reliability of the Banff Patella Instability Instrument (BPII).
• To introduce a disease-specific patient-reported outcome measure for patellofemoral instability.

Main Methods:

• Content validity assessed via a modified 3-stage Ebel procedure.
• Internal consistency measured using Cronbach alpha; test-retest reliability using ICC.
• Construct validity evaluated in 150 patients with patellofemoral instability using ANOVA.

Main Results:

• High content validity achieved with expert panel agreement (83.3%-100%).
• Excellent reliability demonstrated: Cronbach alpha (0.91-0.97) and ICC (0.98).
• Statistically significant construct validity confirmed by BPII score differences across time points (P < .001).

Conclusions:

• The BPII is a valid and reliable patient-reported outcome measure for patellofemoral instability.
• It demonstrates strong content validity and statistically significant construct validity.
• The BPII is suitable for assessing quality of life in patients with recurrent or surgically treated patellofemoral instability.