Swelling in just one leg usually points to a localized issue rather than a full-body problem. It can result from injury or trauma, such as a sprain, fracture, or muscle strain, which causes inflammation and fluid buildup. Prolonged standing or sitting can also trigger swelling when circulation is reduced.
Infections are another possible cause. Conditions like cellulitis often bring redness, warmth, pain, and sometimes fever, and may start from a small cut or insect bite. Because infections can worsen quickly, one-sided leg swelling with these symptoms should be checked by a doctor promptly.
