Osteoarthritis, commonly known as “long bone spurs” and “osteophytes”, is caused by the destruction of joint cartilage, loss of elasticity, loss of strength, and the formation of subchondral bone sclerosis or cystic changes and bone redundancy, resulting in pain and movement disorders, leading to severe disability of the affected limb. This leads to pain and movement disorders, and serious limb disability. Currently, the prevalence of osteoarthritis is increasing globally year by year and has become one of the most common joint diseases in the world, with the prevalence increasing rapidly with age; more than 50% of people older than 65 years have radiographic evidence of osteoarthritis, but 25% have symptoms, and 80% of people older than 75 years have symptoms. The incidence of osteoarthritis of the knee is highest due to the heavy load on the knee joint, high activity, and susceptibility to trauma, strain, and wind and cold stimuli, which can result in impairment of squatting and stairs, severe inversion and flexion contracture deformity, and eventually joint disability. In mild cases of osteoarthritis of the knee, conservative treatment is the mainstay, but when conservative treatment is ineffective, surgical treatment may be required. These include minimally invasive arthroscopic debridement, arthroscopic debridement combined with knee preservation surgery (periprosthetic osteotomy orthopedic surgery) and artificial joint replacement. We currently perform minimally invasive knee debridement and osteotomies to preserve the patient’s original knee and delay or avoid total knee replacement, and perform over a thousand knee surgeries annually. Arthroscopic debridement is useful for removing or repairing free bodies, cartilage fragments, meniscal fragments, and bone fragments that cause mechanical impairment of the joint, and removing synovitis-causing inflammatory factors through intraoperative high-dose joint irrigation to reduce symptoms by eliminating mechanical impairment factors and inflammatory factors. With the development of arthroscopic technology, rapid anesthesia and the concept of accelerated recovery surgery (ERAS), we have standardized surgical management measures to achieve adequate post-surgical analgesia, early mobility and promotion of organ function recovery, thereby reducing post-surgical complications and providing short, flat and fast medical services. To this end, we have introduced day surgery. (1) Knee osteoarthritis cleanup (including synovial cleanup, free body removal, and meniscectomy) (2) Internal fixation removal after anterior and posterior cruciate ligament reconstruction and tibial high osteotomy. (1) Patients with knee pain, strangulation and limitation of motion, with imaging: knee degeneration, combined with free body and/or meniscus injury; (2) Knee joint postoperative internal fixation (after anterior and posterior cruciate ligament reconstruction and tibial high osteotomy). Necessary preoperative tests Routine blood, urine, electrolytes, liver function, kidney function, coagulation, infectious disease screening (hepatitis B, hepatitis C, syphilis, AIDS); chest X-ray, electrocardiogram; optional tests according to the patient’s condition: CT, electromyography, pulmonary function test, echocardiogram, etc. Anesthesia Lumbar anesthesia or nerve block. Surgical procedure: (a) Knee osteoarthritis cleanup (including synovectomy, free body removal, meniscectomy, etc.) 1. Knee synovectomy for traumatic synovitis, chromovillitis, rheumatic and rheumatoid synovitis, synovial crepitus syndrome, etc. Patients with chromovillous nodular synovitis with extensive synovial lesions visible arthroscopically Arthroscopic synovectomy for lesions 2. Arthroscopic free body removal: for the removal of free bodies and foreign bodies in the knee, elbow, hip and ankle joints to resolve the symptoms of joint strangulation and relieve the development of arthritis. The patient’s preoperative X-ray examination shows that there is a high-density shadow in the joint. The intra-articular free body is visible under the arthroscope. Intraoperative arthroscopic visible meniscal degeneration tear Intraoperative arthroscopic meniscoplasty After arthroscopic meniscoplasty, the torn meniscus is given excision and shaping Knee arthroscopy cleaning wound is about 0.5-1.0cm long incision on both sides. (b) Arthroscopic debridement + removal of internal fixation: for arthroscopic debridement and removal of internal fixation after anterior and posterior cruciate ligament reconstruction, tibial high osteotomy, and distal femoral osteotomy. Preoperative X-ray images: Intraoperative X-ray reveals complete removal of the internal fixation portal nail Hospitalization days The standard hospitalization day for patients is 2 days (48 hours). Patients may be discharged if they have a normal temperature, no significant abnormalities in routine laboratory tests, no signs of infection in the wound, no complications and/or comorbidities requiring hospitalization, and no significant swelling of the joint or affected limb. The minimally invasive knee arthroscopy, which becomes a day surgery, not only conforms to the modern concept of rapid rehabilitation, but also responds to public opinion, reduces hospitalization time and costs, and, crucially, solves the problem of difficult hospitalization for the majority of patients.