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Objective <p>Patellofemoral osteoarthritis (PFOA) comprises distinct medial (MPFOA) and lateral (LPFOA) subtypes, yet their specific risk factors remain poorly defined. This study aimed to investigate the independent and interactive effects of patellar morphology (Wiberg classification) and femorotibial rotation (FTR) on the risk of developing compartment-specific PFOA in patients with stable patellofemoral joints.</p> Methods <p>This retrospective, single-center study analyzed 246 knees from 235 patients with stable patellofemoral joints. Patients were categorized into MPFOA and LPFOA groups based on MRI-assessed cartilage damage using the WORMS score. Radiographic and MRI data were used to measure anatomical parameters, including FTR angle, Wiberg patellar type, hip-knee-ankle angle, patellar tilt, and TT-TG distance. Multivariate logistic regression analyses, adjusted for age, sex, and BMI, were performed to identify independent risk factors for MPFOA and LPFOA. The interaction between FTR and Wiberg type was also assessed.</p> Results <p>For MPFOA, Wiberg type I patella (OR = 4.364, 95% CI: 1.910–9.969, <i>P</i> &lt; 0.001) and an FTR angle &gt; 10° (indicative of internal tibial rotation) (OR = 3.497, 95% CI: 1.370–8.926, <i>P</i> = 0.009) were identified as significant independent risk factors. For LPFOA, Wiberg type III patella (OR = 2.916, 95% CI: 1.267–6.712, <i>P</i> = 0.012) and an FTR angle &lt; 0° (external tibial rotation) (OR = 4.601, 95% CI: 1.416–14.946, <i>P</i> = 0.011) were significant predictors. Furthermore, a significant interaction was found between Wiberg type and FTR for both MPFOA (<i>P</i> = 0.032) and LPFOA (<i>P</i> = 0.042), suggesting these factors synergistically influence the compartmental pattern of degeneration.</p> Conclusion <p>MPFOA and LPFOA are associated with distinct and opposing anatomical risk profiles. Wiberg type I patella combined with internal FTR significantly increases the risk of MPFOA, whereas Wiberg type III patella with external FTR predisposes to LPFOA. The interaction between patellar morphology and femoral-tibial rotation alignment highlights the need for comprehensive assessment to accurately stratify risk and guide personalized PFOA interventions.</p> Level of evidence <p>Observational and retrospective (level III).</p>

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Risk factors for osteoarthritis in the medial compartment of the stable patellofemoral joint: FTR angle and Wiberg type I patella

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月5日

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  • Min Li,
  • Huijun Kang,
  • Bo Chang,
  • Xiaomeng Wang,
  • Zhao Li,
  • Lingce Kong,
  • Enzeng Xing,
  • Fei Wang

摘要

Objective

Patellofemoral osteoarthritis (PFOA) comprises distinct medial (MPFOA) and lateral (LPFOA) subtypes, yet their specific risk factors remain poorly defined. This study aimed to investigate the independent and interactive effects of patellar morphology (Wiberg classification) and femorotibial rotation (FTR) on the risk of developing compartment-specific PFOA in patients with stable patellofemoral joints.

Methods

This retrospective, single-center study analyzed 246 knees from 235 patients with stable patellofemoral joints. Patients were categorized into MPFOA and LPFOA groups based on MRI-assessed cartilage damage using the WORMS score. Radiographic and MRI data were used to measure anatomical parameters, including FTR angle, Wiberg patellar type, hip-knee-ankle angle, patellar tilt, and TT-TG distance. Multivariate logistic regression analyses, adjusted for age, sex, and BMI, were performed to identify independent risk factors for MPFOA and LPFOA. The interaction between FTR and Wiberg type was also assessed.

Results

For MPFOA, Wiberg type I patella (OR = 4.364, 95% CI: 1.910–9.969, P < 0.001) and an FTR angle > 10° (indicative of internal tibial rotation) (OR = 3.497, 95% CI: 1.370–8.926, P = 0.009) were identified as significant independent risk factors. For LPFOA, Wiberg type III patella (OR = 2.916, 95% CI: 1.267–6.712, P = 0.012) and an FTR angle < 0° (external tibial rotation) (OR = 4.601, 95% CI: 1.416–14.946, P = 0.011) were significant predictors. Furthermore, a significant interaction was found between Wiberg type and FTR for both MPFOA (P = 0.032) and LPFOA (P = 0.042), suggesting these factors synergistically influence the compartmental pattern of degeneration.

Conclusion

MPFOA and LPFOA are associated with distinct and opposing anatomical risk profiles. Wiberg type I patella combined with internal FTR significantly increases the risk of MPFOA, whereas Wiberg type III patella with external FTR predisposes to LPFOA. The interaction between patellar morphology and femoral-tibial rotation alignment highlights the need for comprehensive assessment to accurately stratify risk and guide personalized PFOA interventions.

Level of evidence

Observational and retrospective (level III).