ACL injuries are common sports injuries of the knee joint, with high-risk sports such as basketball, skiing, soccer, and rugby, mostly seen in adolescents who love sports. Acute ACL injuries are common when the knee joint is sprained during jumping and landing during sports, and sometimes the joint feels misaligned in the hand. Also, ACL injuries may be accompanied by meniscal and/or medial collateral ligament injuries, so early diagnosis and treatment is important. After ACL rupture, the typical symptoms are knee instability and a sense of misalignment, especially when doing sharp turns or sharp stops. For long ACL ruptures, there may also be symptoms of joint aliasing or interlocking due to meniscus tears. Even some movements in daily life such as turning can cause a knee joint misalignment sensation. For acute knee sprains, if the joint is significantly swollen and painful, it is necessary to apply ice immediately and go to the hospital for diagnosis and treatment as soon as possible. Current hospital testing technology is very convenient for diagnosing ACL injuries. Knee MRI can clearly visualize the ACL, as well as observe damage to the meniscus and articular cartilage. Patients with ACL injuries who continue to participate in jumping and twisting sports have repeated instability in the knee joint putting the meniscus and articular cartilage at high risk. Conservative treatment can be used in older patients with minimal sporting demands and simple ACL injuries, which are aimed at restoring most daily activities and cannot meet the demands of strenuous sports. While previous conservative treatment included rest, ice, and brace braking, the new conservative treatment aims at rehabilitation. The rehabilitation process consists of two steps: the first step aims to eliminate the inflammatory response and restore joint mobility and muscle control. Ice is usually used to reduce pain and swelling, and joint mobility and patellar movement can be started immediately, along with muscle strength training to avoid muscle atrophy. The second step can be started once the patient returns to normal gait. The second step emphasizes N-cord and quadriceps strength training with open and closed chain exercises, ranging from high frequency and low intensity to low frequency and high intensity. Balance training and proprioceptive training are then performed. Conservative treatment should use a functional brace, which provides all-around knee stability and allows for a range of motion in patients with ACL injuries. The functional brace serves two purposes: first, to improve proprioception and second, to avoid reinjury. Currently, the classic surgical treatment for ACL rupture is arthroscopic ACL reconstruction surgery. The ruptured ACL can be replaced with an autologous or allogeneic tendon. Surgery should be considered in younger patients with complete ACL rupture, combined with meniscal or other ligament injuries, who participate in sports at a high athletic level. For the timing of surgery for acute ACL injuries, doctors recommend surgery once the joint effusion disappears and joint mobility and quadriceps strength are restored. Functional exercises such as straight leg raising can be started on the second to third day after surgery, and passive knee flexion and extension activities can be practiced for 4 weeks in the range of 0° to 90°, and return to normal in 6 to 8 weeks. After surgery, a brace should be worn for 6 weeks for protection, and the affected limb can be partially weight-bearing under the protection of the brace. When recovered to be able to walk normally you can start fixed bicycle and lower limb muscle strength recovery exercises. Running and jumping exercises can be started 3 months after surgery, simple sports can be resumed 6 months after surgery, and normal sports activities can be basically resumed one year after surgery.