Introduction: The aim of this study was to determine whether participant characteristics and clinical assessments could identify radiographic osteoarthritis (OA) in individuals with clinically diagnosed, symptomatic patellofemoral osteoarthritis (PFOA).
Methods: Participant characteristics and clinical assessments were obtained from 179 individuals aged 50 years and over with clinically diagnosed symptomatic PFOA, who were enrolled in a randomised trial. Anteroposterior, lateral, and skyline X-rays were taken of the symptomatic knee. The presence of radiographic PFOA was defined as “no or early PFOA” (Kellgren and Lawrence [KL] grade ≤1 in the PF compartment) or “definite PFOA” (KL grade ≥2). Diagnostic test statistics were applied to ascertain which participant characteristics and clinical assessments could identify the presence of definite radiographic PFOA.
Results: A total of 118 participants (66%) had definite radiographic PFOA. Univariate analysis identified that older age (>61 years), female sex, higher body mass index (BMI) (>29 kg/m2 ), longer pain duration (>2.75 years), higher maximum knee pain during stair ambulation (>47/100 mm), and fewer repeated single step-ups to pain onset (<21) were associated with the presence of definite radiographic PFOA. Multivariate logistic regression indicated that BMI, pain duration, and repeated single step-ups to pain onset were independently associated with radiographic PFOA and identified the presence of definite radiographic PFOA with an overall accuracy of 73%.
Conclusion: In individuals over 50 years of age with a clinical diagnosis of PFOA, higher BMI, longer pain duration, and fewer repeated single step-ups to pain onset increased the likelihood of radiographic PFOA. However, overall diagnostic accuracy was modest, suggesting that radiographic PFOA cannot be confidently identified using these tests.
Keywords: diagnosis; osteoarthritis; patellofemoral; rehabilitation; sensitivity; specificity.