*2.6. Histological Analysis*

Histological changes were assessed to determine the e ffects of FP-MD and Celecoxib on joint cartilage degeneration. After 3 weeks post-OA induction, the rats were euthanized with CO2, and the affected knee joints were dissected and fixed in 10% formalin for 24 h at 4 ◦C, decalcified with 5% formic acid for 2 weeks, and then dehydrated in graded acetone and embedded in para ffin. Sections (thickness, 4–5 μm) were stained with hematoxylin and eosin (H&E) and Safranin-O/Fast green to evaluate structural cartilage damage and the proteoglycan loss, respectively, and then observed under Carl Zeiss Axio Imager A2 microscope (Carl Zeiss, Deisenhofen, Germany). All stained slides were histologically evaluated and statistically graded on a scale of 0–13 by double-blind observation, according to the modified Mankin scoring system [37].
