In this study,the Autologous chondrocyte implantation (ACI)technology and cell sheet technology are used to Cells Sheet-Autologous Chondrocyte Implantation(CS-ACI) for treating Cartilage Defects.The Safety and Efficacy Study of CS-ACI are evaluated.

All procedures are carried out after obtaining informed written consent from patients. Cartilage tissue is acquired from the Non-weight-bearing area of patients. chondrocyte are isolated and grown in culture for 6-8 weeks. After this time interval, the cells are reprocessed and the cell sheet is obtained. Implantation of the chondrocyte sheet into the Cartilage defect of the keen.The patients will be assessed clinically with scoring systems preoperatively as well as 24 months postoperatively to assess relief of symptoms and joint function. Radiological assessment (MRIs)of the affected joints will be performed at the same time points aforementioned to assess integrity of the formed cartilage. Second look arthroscopy and biopsy will also be performed to histologically assess the repair tissue and grade it via arthroscopic grading system according to the International Cartilage Repair Society guidelines.

Inclusion Criteria:

• Male or female patients, age: between 18 and 50 years
• Defect: isolated ICRS grade III or IV single defect chondral lesions on Articular Cartilage
• Defect size: 2.5 to < 5 cm2 after debridement to healthy cartilage up to 6 mm in depth.
• Nearly intact chondral structure surrounding the defect as well as an intact corresponding joint area
• Informed consent signed and dated by patient and Patient understands the strict rehabilitation protocol and follow-up programme and is willing to follow it
• No ligament damage or ligament damage after reconstruction

Exclusion Criteria:

• Patients younger than 18 years and older than 50 years.
• Arthrofibrosis or Ankylosis
• Arthritis
• Obesity
• Infectious diseases
• the other cases of patients which Doctors determine not participate in the trial