*2.3. Adipocyte Morphology Evaluation*

Adipocytes dimension in ACL and OA IFP was quantified, showing an increase of the cell area in adipocytes of OA IFP compared to ACL IFP (*p* < 0.0001) (Figure 1a,b and Table 2). The number of adipocytes was evaluated, revealing a decrease in OA compared to ACL IFP (*p* = 0.0013) consistent with the increase of the adipocyte area in OA (Figure 1c).


**Table 2.** Infrapatellar fat pad adipocytes characteristics.

ACL = anterior cruciate ligament; OA = osteoarthritis. Data are expressed as median (IQR).

**Figure 1.** Adipocytes morphology evaluation. (**a**) ACL (on the left) and end-stage OA (on the right) adipocytes were reported from HE stained sections and then converted into the corresponding binary images. For each image, adipocytes areas (white regions) were identified and approximated to ellipses (red line). The comparison between adipocytes area (**b**) and number (**c**) for ACL and end-stage OA (Median and IQR) showed the increment of adipocytes size and the decrease of adipocytes number in OA IFP. ACL = anterior cruciate ligament; OA = osteoarthritis.

### *2.4. Gene Expression Analysis and Immunohistochemistry*
