The subchondral bone plate divides the bone marrow, which has a rich vascular plexus, from the articular cartilage, which has no vascular distribution. By developing the subchondral bone, fibroblasts and bone marrow mesenchymal stem cells can enter the area of injury and produce repair tissue that will eventually fill the cartilage defect. Although the repair tissue initially resembles cartilage tissue in appearance, it will eventually regress to fibrocartilage over time. Various angled bone cones are placed under the arthroscope and used to penetrate the subchondral bone and stimulate stem cells to produce cartilage-like tissue. 1. Method: The unstable cartilage is removed and the marginal cartilage is required to be vertical after trimming. The calcified cartilage layer above the subchondral bone plate is removed using a scraping spoon, which should not penetrate the subchondral bone plate. using a perforating awl and a percussion instrument, holes are made in the bed of diseased cartilage at a spacing of 3-4 mm and a depth of approximately 4 mm. the microfracture chisel should be perpendicular to the subchondral bone plate as much as possible when chiseling the holes. blood and fat droplets are seen to ooze out of the bone holes after the procedure. 2. Indications: Local IV degree cartilage degeneration and local traumatic lesions. Small defects (0.5-2cm2) or large injuries but low functional requirements, good quality of cartilage at the edge of the injury area. 3. Contraindications: Significant subchondral bone defects, poor alignment of the knee joint and patients who are uncooperative to treatment. This method is also not recommended for large cartilage injuries because microfractures are less effective in treating large cartilage defects of 4 cm2 or more. 4. Post-operative rehabilitation: After surgery, patients should be lightly weight-bearing for 4-8 weeks; perform 6-8 hours of continuous passive activity every day for 6 weeks; wait until the repaired cartilage tissue matures before resuming sports, a process that takes about 6-9 months. The efficacy of this method is limited by the age of the patient and the area of the cartilage defect, and is better in patients < 30 years of age and in patients with a defect area < 4 cm2. 233 patients were treated with microfracture by Steadman et al. The long-term results were not conclusive. 6. Advantages: simple operation, few complications, reliable near-term results, low cost, and preserves the opportunity for reoperation. 7. Disadvantages: slow repair of cartilage defects, cumbersome rehabilitation program; repair tissue is fibrocartilage rather than hyaline cartilage, the collagen fiber structure in the repair tissue is disorganized throughout the articular cartilage base, and the lack of important membrane-like features in the articular cartilage surface layer may be the main factor leading to cartilage regeneration failure.