There are several reasons for swelling below the knee: unilateral swelling may be due to a venous thrombosis of the lower extremity. Bilateral symmetric swelling may be due to hypothyroidism, peripheral venous stasis due to heart failure, or massive protein urine leakage followed by plasma hypoproteinemia, clinically mainly due to nephrotic syndrome and acute and chronic nephritis. Another factor is the occurrence of rheumatoid arthritis combined with symmetrical sunken swelling of the limbs.