Knee cruciate ligament injury has become a common sports injury and traffic injury in recent years, and the development of arthroscopic technology has further improved the repair and reconstruction of the cruciate ligament, whose advantages are: minimally invasive surgery with little injury, accurate positioning, less chance of infection, no obvious surgical complications, and fast postoperative recovery, which is the best surgical technique for the treatment of cruciate ligament injury at present. Since March 1999, we have been using autologous tendon graft to reconstruct the cruciate ligament of the knee joint under arthroscopy with satisfactory clinical results. Clinical data The group consisted of 130 cases, 86 males and 44 females, aged 16-55 years old. There were 83 cases of right knee and 47 cases of left knee. There were 102 cases of anterior cruciate ligament injury and 28 cases of posterior cruciate ligament injury. Cause of injury: 82 cases of traffic accident injury, 39 cases of sports injury, and 9 cases of direct smash injury. There were 57 cases of combined meniscal injury (medial 45 cases, lateral 12 cases) and 48 cases of combined medial collateral ligament injury. Surgical reconstruction time from injury: <4 weeks in 36 cases, 4-8 weeks in 86 cases, and 16-48 weeks in 8 cases. Treatment In this group of cases, autologous middle 1/3 bone-patellar tendon-bone (B-P-B) was used in 32 cases, autologous double femoral semitendinosus tendon and thin femoral tendon were fixed with absorbable interface screws at both ends in 65 cases, autologous double femoral semitendinosus tendon and thin femoral tendon were fixed with button plate at the femoral end and absorbable interface screws at the tibial end in 33 cases, all In the 57 cases with meniscal injury, 16 were repaired and 41 were repaired or partially resected. Postoperative rehabilitation Animal tests showed that the healing time of the grafted tendon to the bone tract was at least 8 weeks. Therefore, premature overload of functional exercise may cause extraction of the unhealed grafted tendon and decrease its stability. However, over-emphasis on braking will inevitably lead to slow recovery of knee function and even limitation of flexion function. It is recommended to perform static exercise of the quadriceps muscle 24 hours after surgery, requiring knee flexion of 90° within the first week, and to instruct the patient to perform functional exercises in bed, together with CPM machine assisted knee functional exercises 1-2 times/day. knee flexion of 120° within 3 weeks. Within 6 weeks after surgery, the patient should walk short distances without weight-bearing (combined medial collateral ligament injury can be extended appropriately). Gradually start walking on the ground at 8 weeks after surgery. At 3 months after surgery, they started to participate in restorative physical exercise, and at 6 months, they started to participate in regular physical exercise. Results All cases in this group were followed up. The duration was 1-4.5 years, and the mean follow-up time was 2 years and 3 months. The efficacy was evaluated according to the literature criteria and the results are shown in the table.Of the 48 cases with combined medial collateral ligament injury, 46 had medial collateral ligament tightening, compared to the treatment with simple reconstruction of the cruciate ligament:Postoperative knee stiffness was found to be more pronounced in the group with repair of the medial collateral ligament, and restoration of range of motion was more difficult. X-ray and CT were reviewed 3 months after surgery, and MRI was reviewed in 65 cases, all of which showed no significant loosening and dislodgement of the fixation screws. The Lachman test and axial shift test were all negative. The patient was able to walk up and down stairs, jump with one leg bent and run at a slow speed. Reconstruction time Number of cases Excellent Good Poor Excellent rate (%) <4 weeks 36 cases 14 8 12 2 61 4-8 weeks 86 cases 54 28 4 0 95* 16-48 weeks 8 cases 2 0 4 2 25 *P<0.01 compared with <4 weeks and 16-48 weeks Discussion Choice of graft Cross-ligament injury The selection of autologous tendons for reconstruction of grafts is currently dominated by bone-patellar ligament-bone (B-P-B) graft and N cord tendon (semitendinosus tendon, thin femoral tendon) graft. The autologous 1/3 of B-P-B is not only of suitable length but also has better tensile strength than other tissues.Noyes [5] concluded that with the strength of the cruciate ligament in young people as 100%, 1/3 of B-P-B as 175%, single femoral semitendinosus tendon as 75% and thin femoral tendon as 49%, 1/3 of B-P-B is four times stiffer than the cruciate ligament and has sufficient strength for cruciate ligament reconstruction strength, and with bone blocks at both ends for bone-bone healing in the bone tunnel. However, the use of B-P-B for grafts often has a donor area lesion, which is prone to patellofemoral problems. The anterior knee skin incision is located in the active area and has a large incision, which has a higher probability of postoperative patellofemoral pain, causing knee swelling, claudication, patella fracture and reduced muscle strength of the knee extension device. Also, the B-P-B graft is eccentric, the flat ligament at the tunnel opening oscillates anteriorly and posteriorly, and the graft stiffness is high, and patients often experience stiffness. Clinical studies have proved that the initial strength of the semitendinosus tendon and thin femoral tendon bifolded and applied into 4 strands can reach 250%, which can fully meet the tensile strength of the reconstructed cruciate ligament, and this is beneficial to the early rehabilitation activities. The semitendinosus tendon and the thin femoral tendon are only part of the medial knee stabilization structure, so they have less impact on the knee function after excision, and it is easier and less time consuming to excise them with the special tendon extractor. In chronic cases, there was no statistically significant difference in knee stability after long-term follow-up of the reconstruction of the cruciate ligament with either the patellar tendon or the bifemoral semitendinosus tendon. Moreover, the reconstruction of the cruciate ligament with the double femoral semitendinosus tendon was fixed with new absorbable interface screws or button plates through the bone cavities on both sides, instead of using expensive titanium screws, which avoided the contracture of the patellar ligament and infrapatellar capsule after taking the middle 1/3B-P-B, leading to complications such as knee extension stiffness. However, the disadvantage is that the bone tendon healing of the N cord tendon in the tunnel is slower than the bone bone healing, and the formation of a fibrous joint with high viscoelasticity requires adequate prestressing, and the postoperative creep characteristics make the anterior-posterior laxity greater than that of B-P-B. The choice of internal fixation The metal interface screws were mostly used at the ends of the cruciate ligament reconstruction grafts in the early stage, which are characterized by non-absorbability; the interface between the nail and the bone and ligament is prone to loosening; some patients have psychological rejection of the metal foreign body in the knee joint, and in five cases in this group, the metal interface screws were removed by secondary arthroscopic surgery at the request of the patients. Absorbable interface screws are made of SR-PL-LA polypropylene resin, which can expand radially and contract longitudinally after 2h of implantation and produce automatic pressure, and can be absorbed after surgery. 98 cases in this group (65 cases used absorbable screws at both ends and 33 cases used absorbable screws at the tibial end) eliminated patients' foreign body sensation and fear of secondary surgery, and avoided the pendulum effect. In 33 cases of this group, the femoral end was fixed with button plate, and after the ligament implantation and fixation, the tension of the ligament can be increased by rotating the button, and the expansion of the tunnel can be avoided, which is less likely to cause wear and tear of the graft, and the fixation method is simple and quick, which greatly shortens the operation time and provides a quick method for the operator, and also shortens the time of anesthesia and tourniquet application for the patient at the same time. Timing of cruciate ligament reconstruction Studies have shown that reconstructing the cruciate ligament within the first month after injury, during the acute inflammatory phase of the knee joint and when activity is limited, has a higher risk of joint adhesions and loss of joint activity, especially in cases with combined medial collateral ligament injury. 2 cases in our group had significantly limited knee function (<90°) after surgery, and later recovered normal knee movement after re-admission to the hospital for comprehensive treatment. Surgical treatment of the recently damaged knee served to induce scarring at the site where the joint had begun the healing process, prompting the formation of firmer scar tissue that interfered with the motion of the knee joint, which is the process of joint fibrosis. Therefore, after a cruciate ligament injury of the knee, surgical reconstruction is not necessary immediately, but can be treated with non-steroidal anti-inflammatory drugs first, and then reconstructed when the inflammatory exudation of the knee disappears and joint movement is restored 4-8 weeks after the injury, which can reduce postoperative complications, especially knee stiffness.