Cartilage injury remains one of the common clinical problems due to its limited regeneration capacities. Meniscectomy commonly performed for meniscus injury leads to osteoarthritis, but the indication of meniscus repair is limited. We have identified that synovial mesenchymal stem cells(MSCs)are superior to MSCs derived from other tissues in proliferation capacity and in vitro/in vivo chondrogenic potentials. When suspension of synovial MSCs was placed on the cartilage defect for 10 minutes, 60% of the cells attached to the defect site. Based on these basic researches, we started a clinical study for cartilage regeneration by arthroscopic transplantation of synovial MSCs. Additionally, we transplanted synovial MSCs for meniscus injury after meniscus repair. We obtained good clinical results of cartilage regeneration and meniscus healing without any serious side effects. Transplantation of synovial MSCs will be useful for cartilage or meniscus injuries.