(A) Proliferative osteoarthritis The age of onset is more than 40 years old, without systemic diseases. There is no local redness or swelling of the joints, the damaged joints are more common in the weight-bearing knees and spine, there is no wandering phenomenon, muscle atrophy and joint deformity with lipoid hyperplasia or bone wart formation at the edges, normal blood sedimentation and negative RF. (2) Rheumatoid arthritis This disease is especially easy to be confused with rheumatoid arthritis at the onset, and the following points can be distinguished: ① the onset is usually acute, with sore throat, fever and increased white blood cells; ② the involvement of large joints of the extremities is common, as wandering joint swelling and pain, no permanent damage after the disappearance of joint symptoms; ③ often occurs simultaneously with cardiac inflammation; ④ serum anti-streptococcal hemolysin “O (4) serum anti-streptococcal hemolysin “O”, anti-streptococcal kinase and anti-hyaluronidase are positive, while RF is negative; (5) salicylic acid preparations often have rapid and significant efficacy. (iii) Tuberculous arthritis Rheumatoid arthritis should be differentiated from this disease when it is limited to a single joint or a few joints. The disease can be associated with other sites of tuberculosis, such as spinal tuberculosis often has paravertebral abscess, more than two joints at the same time is rare. x-ray examination is not easy to distinguish early, if there is limited destruction of bone or paravertebral abscess shadow, help to diagnose. Tuberculosis culture of joint cavity exudate is often positive. Anti-tuberculosis treatment is effective. (D) Ankylosing spondylitis This disease was previously thought to be a type of rheumatoid arthritis, but it begins in the low iliac joints, not in the small joints of the extremities; synovitis is not obvious, but calcification and ossification are obvious; rheumatoid factor tests are negative, and subcutaneous rheumatoid nodules do not appear; aspirin and other drugs that are not effective in rheumatoid arthritis can be effective in treating this disease. (E) Other connective tissue diseases (with polyarthritis) 1. Systemic lupus erythematosus is not easily distinguished from early rheumatoid arthritis; the former occurs mostly in young women, and synovitis of the proximal interphalangeal joints and metacarpophalangeal joints can also occur, but the joint symptoms are not heavy, and there is usually no cartilage or bone destruction, and the systemic symptoms are obvious, with multi-organ damage. Typically, butterfly or disc-shaped erythema appears on the face. Lupus cells, anti-ds-DNA antibody, Sm antibody, and positive lupus band test are helpful for diagnosis. Scleroderma, which occurs in women aged 20 to 50 years, is easily confused with RA because of symmetrical hand stiffness, finger and knee pain and swelling of the surrounding soft tissues caused by synovitis in the early edema stage. The early stage of the disease is self-limiting, and the swelling often disappears suddenly after several weeks, and Raynaud’s phenomenon appears, which is favorable for the diagnosis of the disease. Sclerosis and atrophy stage shows skin sclerosis, “bitter smile” face is easy to distinguish. 3, mixed connective tissue disease clinical symptoms are similar to RA, but there are high titers of granular fluorescent anti-nuclear antibodies, high titers of anti-soluble ribonucleoprotein (RNP) antibodies positive, while Sm antibodies negative. 4. muscle pain and edema in dermatomyositis are not limited to the vicinity of joints, and cardiac and renal lesions are also common, while joint lesions are rare. ana (+), anti-PM-1 antibody, anti-Jo-1 antibody positive.