Rheumatoid arthritis may cause swelling of the lower limbs, but swelling of the lower limbs may also be caused by renal insufficiency, varicose veins of the lower limbs, etc. Rheumatoid arthritis may involve the joints and cause clinical symptoms such as swelling, morning stiffness and joint pain. 1. Rheumatoid arthritis: Rheumatoid arthritis can involve the joints and lead to joint swelling, morning stiffness, joint pain and other clinical symptoms, so the patient’s lower extremity swelling may be caused by rheumatoid arthritis. 2. Renal insufficiency: patients with renal dysfunction may suffer from proteinuria due to decreased glomerular filtration, which may lead to lower extremity swelling. 3. Varicose veins of the lower limbs: Varicose veins of the lower limbs may cause swelling due to increased pressure and stagnation of blood flow in the veins of the lower limbs. Swelling of the lower limbs may also be caused by other reasons, and it is recommended that patients with this symptom go to the relevant departments of regular hospitals for detailed consultation.