Objective To investigate the effectiveness of free latissimus dorsi myocutaneous flap transplantation combined with external fixation in the treatment of bone and soft tissue defects around the knee joint. Methods A retrospective analysis was conducted on the clinical data of 13 patients with high-energy trauma-induced bone and soft tissue defects around the knee joint admitted between January 2016 and July 2023. Among them, 11 were male and 2 were female, the age ranged from 23 to 61 years, with an average of 35.7 years. The causes of injury included 10 cases of traffic accident, 2 cases of machine entanglement injury, and 1 case of heavy object crush injury. According to the Gustilo-Anderson classification, 11 cases were type Ⅲ B and 2 cases were type Ⅲ C. Post-injury, 2 cases had wound infection and 2 cases had popliteal artery injury. The time from injury to flap repair was 40-49 days, with an average of 27.5 days. The wound size was 18 cm×13 cm to 32 cm×20 cm, all accompanied by distal femoral bone defects and quadriceps muscle defects. After primary debridement, vacuum sealing drainage combined with external fixation was used for treatment. In the second stage, free latissimus dorsi myocutaneous flaps were transplanted to repair soft tissue defects, with the flap size ranging from 20 cm×15 cm to 34 cm×22 cm. The donor sites of 9 flaps were directly sutured, and 4 cases with large tension were repaired with a keystone flap based on the posterior intercostal artery perforator. At 6-15 months postoperatively, with an average of 10.5 months, 11 patients underwent knee arthrodesis surgery; 2 patients with large bone defects at the distal femur and proximal tibia underwent multi-segment bone transport reconstruction of the bone defect. At last follow-up, the recovery of the flap and the donor site was recorded, and the function of the shoulder joint was evaluated by the American Shoulder and Elbow Surgeons (ASES) score, and the function of the affected knee joint was evaluated by the Knee Society Score (KSS). ResultsAll the flaps survived after operation, the wounds and donor site incisions healed by first intention. All 13 patients were followed up 15-55 months, with an average of 21.6 months. Four patients who underwent the restoration of the donor site with the thoracodorsal keystone perforator flap had obvious scar hyperplasia around the wound, but no contracture and symmetrical breasts on both sides. At last follow-up, the appearance and texture of the flaps were good; the bony fusion of the knee joint was good, and the range of motion and function recovered well; the shoulder joint function on the flap-harvested side was not significantly affected, and the range of motion was satisfactory. The ASES shoulder joint score of the latissimus dorsi muscle-harvested side was 85-95, with an average of 89.5. The knee joint function KSS score was 75-90, with an average of 81.2. ConclusionFree latissimus dorsi myocutaneous flap transplantation combined with external fixation for the treatment of bone and soft tissue defects around the knee joint caused by high-energy trauma can effectively preserve the integrity of the limb and soft tissues, and improve the patient’s ability of self-care. At the same time, it can repair bone and soft tissue defects and reconstruct the stability of the knee joint.