Analysis of Risk Factors on Patellofemoral Osteoarthritis: Distribution Characteristics and Radiographic Parameters of Patellofemoral Joint

Abstract

Objective: The risk factors for the degeneration of the patellofemoral joint (PFJ) have not been adequately and thoroughly studied. This study aimed to analyze the population distribution characteristics of patients with patellofemoral osteoarthritis (PFOA) and assess the correlation between PFOA and radiological parameters, including patella morphology, PFJ congruity, and patellar alignment. Moreover, the risk factors across various demographic groups were further analyzed.

Methods: A retrospective analysis was conducted to examine the population distribution characteristics of PFOA patients from September 2020 to September 2023. Radiological parameters of the PFJ were measured from the anteroposterior and lateral views of knee joint as well as axial view of patella using X-ray imaging and the PACS imaging system at the First Affiliated Hospital of Kunming Medical University. These parameters included patella morphology (patella type, width, thickness, and Wiberg index), PFJ congruity (patella height, Wiberg angle, sulcus angle, and lateral patella angle), and patellofemoral alignment (patella tilt angle, displacement, and lateral patellofemoral angle). PFOA severity was classified according to the Iwano PFJ radiological classification, and its correlation with the aforementioned parameters was examined. Additionally, risk factors for PFOA across different populations were further evaluated.

Results: The study included 1080 patients according to the inclusion and exclusion criteria. Age, female gender, overweight or obesity, and manual workers were significantly associated with PFOA. Moreover, type III patella (OR = 3.03, p < 0.05), greater patella width (OR = 1.12, p = 0.01), sulcus angle (OR = 1.04, p < 0.01), patella tilt angle (OR = 1.13, p < 0.01), and patella displacement (OR = 1.22, p < 0.01) as well as smaller patella thickness (OR = 0.87, p < 0.01), Insall-Salvati index (OR = 0.24, p = 0.04), and lateral patellofemoral angle (OR = 0.93, p = 0.02) were identified as risk factors for PFOA. Furthermore, greater patella thickness (OR = 1.17, p < 0.05) and smaller patella displacement (OR = 0.79, p < 0.01) correlated with higher Kujala patellofemoral scores. Discrepancies in risk factors across different populations were also observed.

Conclusions: Older age, female gender, obesity, manual workers, and specific aberrations in patellofemoral parameters are predictive factors for PFOA. Additionally, greater patella thickness and smaller patella displacement were associated with increased severity of clinical symptoms. Thus, more attention should be paid to the discrepancies that exist in different populations.

Keywords: knee; osteoarthritis; patellofemoral joint; radiology; regression analysis.

FIGURE 1

Iwano patellofemoral joint radiological classification. (A) Stage I: Mild narrowing of the joint space, where the narrowest part of the articular surface is ≥ 3 mm. (B) Stage II: Moderate narrowing of the joint space, with the narrowest part of the articular surface < 3 mm, but without bony contact. (C) Stage III: Severe narrowing of the joint space, with partial bony contact encompassing less than one‐quarter of the joint space. (D) Stage IV: Extremely severe narrowing of the joint space, with complete contact between the bony joint surfaces.

FIGURE 2

(A1–A4) Wiberg and Baumgartl classification of the patella. (B) Patella width; Patella thickness; (C) Wiberg index; (D) Lateral patella angle; (E) Patella tilt angle; (F) Wiberg angle; (G) Sulcus angle; (H) Lateral patellofemoral angle; (L) Patella displacement; (M) Insall–Salvati index.

FIGURE 3

Population distribution characteristics of PFOA patients. (A) Proportion of age distribution; (B) proportion of gender distribution; (C) proportion of BMI distribution; and (D) proportion of profession distribution.