Histomorphology of treated knee joints of Balb/C mice. The joints were analyzed 12 weeks after the first intra-articular injection of (a), (c), (e) the control solution or (b), (d), (f) 100 μM 2-methoxyestradiol (2ME2). In the control joints, representative coronar sections of (a) the patellofemoral joint, as well as (c) the medial knee compartment and (e) the lateral knee compartment, did not show relevant signs of cartilage degeneration or osteophyte formation. (c) The menisci remained intact. 2ME2-treated joints were characterized by significant osteophyte formation (asterisks) and degeneration of the articular cartilage in (b) the patellofemoral joint, as well as in the (f) lateral and (d) medial knee compartments. Toluidine blue staining. Bar = 1 mm. P, patella; F, femur; T, tibia.