Fig 1.
Histopathological assessment of regions in the sagittal section at the center of the patellofemoral joint.
(A) Assessment of the articular cartilage with hematoxylin and eosin staining was performed at each region (2-mm wide). (B) Infrapatellar fat pad. Scale bar = 2 mm. Articular cartilage region: proximal femur (FP), central femur (CF), distal femur (DF), and patella.
Fig 2.
Histopathological features according to the Osteoarthritis Research Society International grade and staining method.
Slides from the (A) patellofemoral joint and (B) tibiofemoral joint were stained with hematoxylin and eosin and safranin O. Grade 1, surface intact; grade 2, surface discontinuity; grade 3, vertical fissures; grade 4, erosion; grade 5, denudation and reparative tissue surface present; and grade 6, deformation and osteophyte formation. Scale bar = 1 mm (grades 1–5) and 2 mm (grade 6).
Table 1.
Synovitis score and fibrosis score of the infrapatellar fat pad.
Fig 3.
Representative histopathological changes of articular cartilage in the patellofemoral joint induced using 0.2-mg monosodium iodoacetate.
The upper and lower sections present an overview of the patellofemoral joint stained with hematoxylin and eosin (HE) and safranin-O fast green. Deformation of the whole joint is not observed. Weak safranin-O staining of the cartilage matrix is observed at 4 weeks. However, staining of the cartilage matrix showed slight regeneration at the margin at 8 and 12 weeks. The middle section shows high magnification images of the contact area of the articular cartilage of the patella and femur stained with HE. Early-stage osteoarthritic histological changes, such as fibrillation and fissuring, are not detected. Scale bar = 2 mm (upper and lower sections) and 1 mm (middle section).
Fig 4.
Representative histopathological changes of articular cartilage in the patellofemoral joint induced using 1.0-mg monosodium iodoacetate.
The upper and lower sections present the overview of the patellofemoral joint stained with hematoxylin and eosin (HE) and safranin-O fast green. Deformation of the whole joint is observed after 8 weeks. Weak safranin-O staining of the cartilage matrix is observed during the experimental period. The middle section shows high magnification images of the contact area of articular cartilage of the patella and femur stained with HE. Early-stage osteoarthritic histological changes are observed after 4 weeks, and end-stage osteoarthritic changes, such as the eburnation or deformation, are observed after 8 weeks. Scale bar = 2 mm (upper and lower sections) and 1 mm (middle section).
Fig 5.
Characteristic histological changes of the articular cartilage in the patellofemoral joint.
A: In the left image, normal articular cartilage and chondrocytes of the control group are shown. In the right image, histological changes of the chondrocyte nuclei are observed, including weak hematoxylin and eosin (HE) staining of nuclei, nuclear enlargement, disintegration of nuclei, and differences in nuclear size at the patella and femur (white triangles). B: Replacement of the articular cartilage surface with the membranous structure (black triangles) is shown stained with HE (left image) and safranin-O fast green (right image). Scale bar = 200 μm (A) and 1 mm (B).
Fig 6.
Articular cartilage degeneration in the regions of the patellofemoral joint using the OARSI scoring system.
A: Changes in the OARSI scores of each region according to time. B: Differences in the OARSI scores between regions. Boxplots display median values and interquartile ranges. Articular cartilage region: proximal femur (FP), central femur (CF), distal femur (DF), and patella. There is no statistically significant difference in any of the results. OARSI, Osteoarthritis Research Society International.
Fig 7.
Articular cartilage degeneration in the tibiofemoral joint using the OARSI scoring system.
Changes in the OARSI scores over time in the 0.2-mg and 1.0-mg groups. Boxplots display median values and interquartile ranges. In the 0.2-mg and 1.0-mg groups, the scores of the femur and tibia tended to increase over time, but there were no significant differences. OARSI, Osteoarthritis Research Society International.
Fig 8.
Representative histopathological features and changes in infrapatellar fat pad inflammation scores over time.
Histological features were examined according to the infrapatellar fat pad inflammation scores for the (A) surface and (B) body of the infrapatellar fat pad. Changes in the (A) synovitis and (B) fibrosis scores of the infrapatellar fat pad were analyzed by group over time. The synovitis score is deceased over time. The fibrosis score in the 0.2-mg group remains low, but the score in the 1.0-mg group is increased over time. Scale bar = 200 μm.