Sore and swollen knees in pregnancy may be caused by the increased burden on the knees after pregnancy, or considered to be caused by knee osteoarthritis, knee synovitis and other diseases. 1. Increased knee burden: pregnant women during pregnancy, with the gradual increase in gestational weeks, the weight will gradually increase, the burden on the knee also increased, muscles, ligaments and other tissues will appear fatigue, manifested as knee soreness. This is a normal phenomenon, no need to worry, to ensure adequate rest. 2. Knee osteoarthritis: the etiology and pathogenesis of knee osteoarthritis is not yet clear, may be due to obesity, inflammation, trauma, genetics, infection and other factors. Patients will experience joint pain, limited joint movement, joint swelling and other symptoms. 3. Knee synovitis: knee synovitis may be caused by biochemical stimulation, knee injury, obesity and other factors. Patients mainly manifested as knee joint swelling, pain, limited activities, etc., will appear pregnant knee soreness. There are many causes of pregnancy knee soreness, patients should go to the hospital, to identify the cause of the disease.