Are there three main subgroups within the patellofemoral pain population? A detailed characterisation study of 127 patients to help develop targeted intervention (TIPPs)

James Selfe, Jessie Janssen, Michael Callaghan, Erik Witvrouw, Chris Sutton, Jim Richards, Maria Stokes, Denis Martin, John Dixon, Russell Hogarth, Vasilios Baltzopoulos, Elizabeth Ritchie, Nigel Arden, Paola Dey