Translation, reliability and validity of the Turkish versions of Norwich Patellar Instability score and The Banff Patellar Instability Instrument 2.0.

Background: Current treatment options for patellofemoral (PF) instability have required functional scoring systems. The Banff Patellar Instability Instrument (BPII) 2.0 and Norwich Patellar Instability (NPI) scores were explicitly created to meet the need to evaluate PF instability.