(a) Time-dependent changes in average percentage of TUNEL-positive chondrocytes in the UF layer after surgery. The average percentages of TUNEL-positive chondrocytes in the resection group at 1 and 2 weeks were significantly higher than those in the sham group. The average percentage of TUNEL-positive chondrocytes at 1 week was significantly higher than that at 4 weeks. The average percentage of TUNEL-positive chondrocytes at 2 weeks was significantly higher than those at 4 weeks and 6 weeks. Shaded bars: Resection group, Unshaded bars: Sham group Safranin-O staining of histological sections of at 2 weeks in UF layer; (b): resection group, (d): sham group. (c) and (e) are magnified views of the boxed part in (b) and (d) that are TUNEL of histological sections at 2 weeks in UF layer. The TUNEL-positive chondrocytes are brown (arrow).