Abstract
Knee osteoarthritis is a common degenerative or posttraumatic condition associated
with significant pain and disability among patients. Isolated patellofemoral osteoarthritis
(PFOA) occurs in approximately 24% of women and approximately 11% of men aged >55
years presenting with knee pain. In contrast to the tibiofemoral compartments, the
current literature lacks a reliable magnetic resonance imaging (MRI) scoring system
for quantitative evaluation of patellofemoral cartilage degeneration. This study aimed
to describe, apply, and assess the interobserver reliability of a novel MRI scoring
system for assessment of the patellofemoral cartilage. Patients who underwent patellofemoral
arthroplasty for isolated PFOA between January 2012 and December 2021 were identified.
Preoperative MRI scans were performed on 3.0-Tesla magnets utilizing dedicated extremity
coils and standardized clinical imaging protocols consistent with International Cartilage
Regeneration and Joint Preservation Society (ICRS) guidelines for the assessment of
articular cartilage. A novel semiquantitative MRI patellofemoral scoring system included
assessment of patellar and trochlear cartilage, bony architecture, patellofemoral
alignment, and synovitis. Interobserver agreement was assessed using Cohen's Kappa
coefficient for categorical variables, and the intraclass correlation coefficient
(ICC) was used for the total score. A total of 72 knee MRIs were included in the final
analysis. Patellar bone edema (kappa = 0.61) and patellar cysts (kappa = 0.59) demonstrated
moderate interobserver agreement. All cartilage features, trochlear bone edema and
cysts, osteophytes, subchondral remodeling, patellar height, and synovitis demonstrated
good interobserver agreement (kappa > 0.61). Patellofemoral alignment and total score
demonstrated excellent interobserver agreement (kappa > 0.81). The novel MRI scoring
system for PFOA proposed in this study represents a comprehensive method to assess
patellofemoral joint cartilage degeneration, including evaluation of patellar and
trochlear cartilage changes, bony architecture, patellofemoral alignment, and synovitis.
Importantly, all features of the scoring system demonstrated at least moderate interobserver
agreement, with the majority of variables and total score demonstrating good to excellent
agreement.
Keywords
patellofemoral - osteoarthritis - arthroplasty - magnetic resonance imaging
