Classification approaches used to grade radiographic patellofemoral osteoarthritis: A scoping review

Conduct a scoping review to describe the use and application of different radiographic classification approaches to grade patellofemoral osteoarthritis (PFOA) in literature published during a representative period (2014-2018), and describe reported measurement properties of these grading criteria.

The scoping review was conducted in accordance with PRISMA-ScR guidelines. Eight electronic databases were searched using keywords relating to "patellofemoral" and "radiograph". Two independent assessors screened each record for eligibility. English-language studies published in the years 2014 to 2018 were included if they acquired patellofemoral joint (PFJ) radiographs, described the method of radiograph acquisition, and reported grading PFOA. We excluded non-human and cadaveric studies, single-case studies, and studies with mean participant age <10 years. Studies that reported measurement properties underwent quality appraisal using the COSMIN Risk of Bias Tool. Descriptive statistics were reported.

Of 18,678 records identified, 177 articles were selected. Twenty-six classification approaches to grade radiographic PFOA were reported, with Kellgren-Lawrence (KL) (n = 70, 40 %), OsteoArthritis Research Society International (OARSI) (n = 26, 15 %), and Iwano (n = 25, 14 %) most prevalent. Axial projections (n = 81, 46 %) were most commonly used to grade PFOA, followed by lateral (n = 31, 18 %) and frontal (n = 16, 9 %) projections. KL was most frequently used across settings, disciplines, and regions. Reliability data was reported by 32 (18 %) studies.

Multiple radiographic OA classification approaches were used to grade PFOA during the representative period, although few are specific to the PFJ. We recommend that a reliable and valid PFOA radiographic grading approach be developed using standardized PFJ radiograph acquisition techniques.