The purpose of this trial is to investigate the safety and effect of CaReS-1S to repair knee cartilage defects.

CaReSR-1S is a sterile, ready for use round implant based on a dense matrix of native Collagen type I. It is indicated for the defect filling of focal, full layer and clearly defined knee and ankle cartilage defects of longest diameter 1.1-2.2cm. The fixation of CaReSR-1S is made for all sizes with fibrin glue, whereas the 11 mm implants also allow a press-fit anchoring due to the elasticity of the implant.

The physical nature of the CaReSR-1S allows the in-growth of healthy chondrocytes, as well as progenitor cells from the surrounding healthy tissue.

Inclusion Criteria:

1. Aged from 18 to 55 years old;
2. Diagnosed with isolated knee cartilage defects in condyles of femur by arthroscopy, and the longest diameter is 1.1-2.2cm. The degree of the cartilage defects is Outerbridge IV degree or III degree but approximate to IV degree;
3. Outerbridge degree of cartilage in the other articular facet ≤Ⅱ;
4. Normal lower limb mechanical force line (varus or valgum < 5°);
5. Skeletal mature;
6. 18Kg/M2 ≤ BMI ≤ 30Kg/M2;
7. Agree to sign the informed consent form;
8. Can cooperate in a post-operative rehabilitation program.

Exclusion Criteria:

1. Superficial cartilage defects;
2. Concomitant with subchondral bone defect;
3. Varus or valgum > 5°;
4. Serious meniscus injury;
5. Fractures around the knee;
6. Cannot join in the post-operative rehabilitation program;
7. The contralateral lower-limb cannot stand weight-bearing;
8. A history of knee surgery within 6 months;
9. Secondary arthritis affecting cartilage;
10. Serious arthrocleisis;
11. Undergoing clinical trial;
12. Serious illness of the heart, lung, and other vital organs;
13. Liver function test equal to two times or greater than the upper normal limits; serum creatinine equal to two times or greater than the upper normal limit;
14. Have a contagious disease;
15. Allergic to the agents;
16. Lactating or pregnant women;
17. Serious neuropathy or mental disease;
18. Be addicted with drug or alcohol.