Sex-Differences in Infrapatellar Fat Pad Size in Runners After Knee Surgery and Associations With Patellofemoral-Related Symptoms: TRAIL Cohort Cross-Sectional Study.

The study aimed to examine the association between knee surgery and infrapatellar fat pad volume in female and male runners, and the association between fat pad volume and patellofemoral-related symptoms among runners with knee surgery. This study presents a secondary exploratory analysis of a prospective cohort study. Data from female and male runners with (n = 104, 49% female) or without (n = 99, 52% female) knee surgery were included. Fat pad volumes were measured from knee magnetic resonance images. Patellofemoral-related symptoms were evaluated using the patellofemoral pain and osteoarthritis subscale of the Knee injury and Osteoarthritis Outcome Score. Linear regression models were used to assess the associations between prior knee surgery and fat pad volume in females and males, and zero-inflated beta regression models were used to evaluate the associations between fat pad volume and patellofemoral-related symptoms in the knee surgery group. All models were adjusted for age, body mass, and height. Females with prior knee surgery had a smaller fat pad volume (mean difference [95% CI]: -1.80 cm3 [-3.02, -0.57], p = 0.004) than controls. However, this was not observed in males (0.30 cm3 [-1.39, 2.00], p = 0.723). Among runners with prior knee surgery, fat pad volume was not associated with symptoms in either females (average marginal effects [95% CI]: -0.035 [-0.831, 83.10], p = 0.931) or males (0.255 [-0.233, 23.30], p = 0.306). Females, but not males, exhibit a smaller fat pad volume after knee surgery compared with no surgery controls. Among runners with a history of knee surgery, fat pad volume does not appear to be associated with patellofemoral-related symptoms.