【Overview】 Osteoarthritis (OA) is one of the most common joint diseases. It is a chronic joint disease characterized by degeneration of articular cartilage, destruction an? and osteophytes as a chronic joint disease. The occurrence of this disease is associated with aging, obesity, inflammation, trauma, joint overuse, metabolic disorders and genetics. Osteoarthritis is more prevalent after middle age and is more common in women than men. The prevalence of the disease ranges from 10% to 17% in people aged 40 years, 50% in people aged 60 years or older, and up to 80% in people aged 75 years or older. The disease has a certain rate of disability. The disease is divided into primary osteoarthritis and secondary osteoarthritis according to its cause. The former refers to osteoarthritis of unknown cause, which is related to genetic and physical factors and is mostly seen in middle-aged and elderly people; the latter is secondary to joint trauma, congenital or hereditary diseases, endocrine and metabolic diseases, inflammatory arthropathies, endemic arthropathies, and other osteoarthropathies. It is sometimes difficult to distinguish primary osteoarthritis from secondary osteoarthritis. Questioning and physical examination can help determine the cause. Imaging can help in the diagnosis of secondary osteoarthritis. The disease is divided into symptomatic osteoarthritis and radiographic osteoarthritis according to the presence or absence of clinical symptoms. The former is accompanied by obvious clinical symptoms of osteoarthritis, while the latter has no clinical symptoms but only radiographic osteoarthritis manifestations. Clinical manifestations】 1. Common symptoms and signs The disease is common in the knee, hip, hand (distal interphalangeal joint, first carpometacarpal joint), foot (first metatarsophalangeal joint, heel), spine (cervical and lumbar spine) and other joints that carry more weight or activity. (1) Joint pain and pressure pain The most common manifestation of this disease is localized pain and pressure pain in the joints. The weight-bearing joints and hands are most likely to be involved. It is usually mild or moderate intermittent pain in the early stage, which improves with rest and worsens with activity. There may be localized pressure pain in the joints, which is especially noticeable in the presence of joint swelling. (2) Enlargement of the joint In the early stage, there is limited swelling around the joint, and as the disease progresses, there may be diffuse swelling of the joint, bursal thickening or joint effusion. (3) Morning stiffness Patients may experience stiffness in the morning or after a period of rest, called morning stiffness, which may be relieved by activity. The duration of morning stiffness usually ranges from a few minutes to ten minutes, but rarely exceeds half an hour; (4) Joint friction sounds (sensation) Most often seen in the knee joint. Due to the destruction of cartilage and roughness of the joint surface, bone rubbing sound (sensation) occurs when the joint is moved; (5) Restricted joint movement Due to joint swelling and pain, reduced activity, muscle atrophy, soft tissue contracture, etc. causing joint weakness and restricted movement. It occurs slowly, with early signs of joint immobility and later a decrease in the range of joint movement. It can also occur as a result of free bodies or cartilage fragments in the joint, which can cause “locking” when moving. (1) Hand The distal interphalangeal joint is the most commonly involved, showing bony enlargement on both sides of the extensor side of the joint, called Heberden’s node. The proximal interphalangeal joint is called Bouchard’s node when it is present on the extensor side. It may be associated with mild localized erythema, pain, and tenderness of the nodule. The involvement of the first carpometacarpal joint may result in a square hand deformity due to osteophytes at its base and a snake-like deformity due to hyperplasia and lateral subluxation of the finger joints. (2) Knee Knee involvement is the most common in clinical practice. Risk factors include obesity, knee trauma, and meniscectomy. The main manifestation is knee pain, which is aggravated by activity, more pronounced after descending stairs, and relieved after rest. In severe cases, internal or external knee valgus deformity may occur. There is localized swelling, pressure pain, and limitation of flexion and extension movement in the joint, and most of them have bone friction sound. (3) Hip The hip joint is more commonly involved in men than in women, and more often unilaterally than bilaterally. The pain is mostly localized as intermittent dull pain, which may become persistent with the development of the disease. In some patients, the pain can radiate to the groin, inner thighs and buttocks. The hip joint motion is mostly limited by internal rotation and external rotation, followed by internal retraction, external rotation and extension. Gait abnormalities may be present. (4) Foot The metatarsophalangeal joint is often involved and may present with localized pain, pressure and bony hypertrophy, as well as deformities such as bunions. Bone spurs may appear on the bottom of the foot, causing difficulty in walking. (5) Spine The cervical spine is commonly involved, and the third and fourth vertebrae of the lumbar spine are the most frequent sites. There may be hyperplasia and osteophytes of the vertebral body and posterior synovial joints, causing local pain and stiffness, and corresponding radiological pain and neurological symptoms when local blood vessels and nerves are compressed. Compression of the vertebrobasilar artery by cervical spine involvement may cause symptoms of inadequate blood supply to the brain. Intermittent claudication and cauda equina syndrome can occur when lumbar spine osteophytes lead to spinal stenosis.