Females, but not males, exhibit a smaller fat pad volume after knee surgery compared with no surgery controls, and among runners with a history of knee surgery, fat pad volume does not appear to be associated with patellofemoral-related symptoms.
Female runners with prior knee surgery had significantly smaller infrapatellar fat pad volumes compared to female controls without surgery.
Male runners with prior knee surgery did not show a significant difference in infrapatellar fat pad volume compared to male controls without surgery.
Among runners with prior knee surgery, infrapatellar fat pad volume was not associated with patellofemoral-related symptoms in females.
Among runners with prior knee surgery, infrapatellar fat pad volume was not associated with patellofemoral-related symptoms in males.
The study identified a sex-specific association between knee surgery history and infrapatellar fat pad volume, with the effect present only in females.
This research suggests that the infrapatellar fat pad — a cushioning structure located just below the kneecap — may be affected differently by knee surgery depending on a person's sex. In a study of over 200 recreational runners, women who had previously undergone knee surgery had measurably smaller fat pads (about 1.8 cubic centimeters smaller on average) compared to women who had never had knee surgery. This difference was not seen in men, suggesting that the fat pad may be more vulnerable to surgical effects in women, possibly due to biological differences in tissue response or healing. Despite this structural difference in women, the study found that the size of the fat pad was not linked to knee pain symptoms around the kneecap in either men or women who had undergone surgery. This means that having a smaller fat pad after surgery did not necessarily translate into more patellofemoral (kneecap-related) pain or worse outcomes as measured by a standardized knee symptom questionnaire. This research matters because it highlights that knee surgery may have sex-specific effects on joint structures, which could be relevant for rehabilitation and monitoring after surgery. However, since fat pad size alone was not associated with symptoms in this group, other factors likely play a role in determining who experiences kneecap-related pain after surgery. Clinicians and researchers may need to consider sex as an important variable when studying joint tissue changes and recovery following knee operations.
Upload your bloodwork. We'll cross-reference your results against this study and 4,700 others.
Upload Your LabsHart H, Crossley K, Mentiplay B, Sylvestre E, Haberfield M, Girdwood M, et al.. (2026). Sex-Differences in Infrapatellar Fat Pad Size in Runners After Knee Surgery and Associations With Patellofemoral-Related Symptoms: TRAIL Cohort Cross-Sectional Study.. Journal of orthopaedic research : official publication of the Orthopaedic Research Society. https://doi.org/10.1002/jor.70300