The common causes of increasingly curved legs are osteoarthritis of the knee, rheumatoid diseases, etc., as follows: 1, osteoarthritis of the knee: is the most common cause of knee deformation, can make the knee joint inversion deformity, the patient will show O-shaped leg, and the appearance of exotropic deformity, the patient will show X-shaped leg. Lower extremity force line change, accompanied by joint pain and limited activity, usually artificial joint replacement surgery to relieve clinical symptoms. 2, rheumatoid disease: rheumatoid arthritis can also lead to joint pain, limited activity, long-term uncontrolled, may occur joint function destruction and joint shape change, patients can appear joint deformity, calf bending, through surgery to completely relieve . Patients with increasingly bent legs are treated early to enable satisfactory control of symptoms, otherwise it can affect the weight bearing of the lower limbs and lead to significant aggravation of the disease.