Figure 4. Gross view and grading of repaired regions.

Most osteochondral defects in the 2-week group and all of the defects in the blank group were covered by fibrous-like tissue that infiltrated deep into subchondral bone; irregular surfaces were also observed (A–C). Defects in the 4- and 8-week groups were primarily repaired by glistening, white cartilage-like tissue and bone-like tissue exhibiting relatively smooth surfaces, good integration, and cartilage thickness similar to native structures (D–F). The detailed gross-view grading was listed in the grading table (G). Black arrows indicate repaired regions.