Characteristics of osteoarthritis: a joint lesion that begins with cartilage degeneration. Statistical analysis shows that 80% of people over the age of 50 have arthritis, with the spine and knee being the most commonly affected joints. It is the number one cause of disability in the elderly and is also known as the undead cancer. The pathology of osteoarthritis: degeneration, wear and tear of articular cartilage, loss of subchondral bone, sclerosis, cystic change of subchondral bone hematoma, formation of bone redundancy, synovial hyperplasia, effusion, degeneration and fibrosis of ligaments and menisci, muscle atrophy, and eventually extensive destruction of joint surfaces and joint deformity. Classification of osteoarthritis: Primary osteoarthritis apparently arises spontaneously, but may also be associated with some minor recurrent injury as well as joint degeneration, heredity, body fat, middle-aged and elderly women with extensive lesions. Secondary osteoarthritis is caused by a known disorder, usually due to trauma, and is most often seen in young adults with limited lesions. Clinical symptoms of osteoarthritis: recurrent joint pain (pain going up and down stairs, squatting pain, walking pain), joint swelling, joint stiffness, deformity, and impaired movement. As people age, an increasing percentage of people develop osteoarthritis in one or more joints. There are two main reasons for this condition: First, human life expectancy is increasing (China’s fifth census [2000] 10.26% > 60 years old. The second is the increase in sports trauma as people of all ages improve and maintain their vitality through sports and recreational activities. In the past, treatment of osteoarthritis was generally conservative, with severe joint lesions for some patients resulting in major surgery such as arthrotomy cleanup, osteotomy, or replacement of artificial joints. With the invention of arthroscopic surgery, a newer, minimally invasive surgical treatment concept based on less trauma has emerged and been developed. Osteoarthritis is divided into early, intermediate and late stages. The three stages of treatment for osteoarthritis of the knee are early conservative treatment with Chinese and Western medicine, intermediate minimally invasive arthroscopic cleanup surgery, and late arthroscopic cleanup osteotomy or artificial joint replacement surgery. When osteoarthritis occurs in the knee, the first treatment is conservative, including proper rest, weight loss, oral pain medication and non-steroidal anti-inflammatory drugs, and occasionally intra-articular steroid injections. Intra-articular injections of hyaluronic acid may also be used. When conservative treatment fails, minimally invasive arthroscopic surgery can be performed, including flushing the inflamed joint, cleaning the cartilage surface and ruptured meniscus, removing part of the synovial membrane and sensitive bones that cause soft tissue symptoms, and decompressing the subchondral bone bore. If the degree of joint degeneration has become quite severe and various treatment measures cannot relieve the symptoms, arthrotomy to clean up the osteotomy, total knee artificial joint replacement or unicondylar replacement surgery may be used.